在 Swift 4 中解码通用 类 的可编码树
Decoding a codable tree of generic classes in Swift 4
目标
我需要以树状方式互连的通用对象的表示。这棵树及其对象应具有以下特征：
- 应该可以用 3 个部分构建一棵树：trunk、branch 和 apple
- 无法将父级添加到 trunk
- 其中一个trunk只能获取多个branch节点作为子元素
- 其中一个 branch 只能有多个 apple 节点作为子元素
- 其中 branch 只能有 trunk 或 branch[= 类型的父级84=]
- 无法将子元素添加到 apple
- 检查有效配置应该在编译时>>使用泛型
- 它应该可以通过实现
Codable 协议来编码
- 所以可以编码成JSON
- 并从 JSON
解码
作为这个问题末尾的一个例子，我创建了一个满足所有要求但只有一个要求的游乐场：
从 JSON
解码树
示例代码的解释
一棵树由节点组成，在本例中为 TreePartNodes，它们正在实施 TreePartNodeBase 协议。
此示例中的树是一个 AnyTreePartNode 数组，它们也实现了 TreePartNodeBase 协议并包装了一个实现 TreePartNodeBase 协议的对象，该协议应该是通用的 TreePartNode (TreePartNode<Trunk>、TreePartNode<Branch> 或 TreePartNode<Apple>).
A TreePartNode 具有类型 AnyTreePart 的 属性 treePart。 AnyTreePart（类似于AnyTreePartNode）包装一个实现了TreePart协议（Trunk、Branch或Apple）的对象。
所有这些 类 都在实施 Codable 和 Equatable。
代码已准备好粘贴到 Xcode 游乐场
import Foundation
///////////// TreePart -> implemented by Trunk, Branch, Apple and AnyTreePart
protocol TreePart: Codable {
var name: String { get set }
func isEqualTo( _ other: TreePart ) -> Bool
func asEquatable() -> AnyTreePart
}
extension TreePart where Self: Equatable {
func isEqualTo( _ other: TreePart ) -> Bool {
guard let otherTreePart = other as? Self else { return false }
return self == otherTreePart
}
func asEquatable() -> AnyTreePart {
return AnyTreePart( self )
}
}
///////////// AnyTreePart -> wrapper for Trunk, Branch and Apple
class AnyTreePart: TreePart, Codable {
var wrappedTreePart: TreePart
var name: String {
get {
return self.wrappedTreePart.name
}
set {
self.wrappedTreePart.name = newValue
}
}
init( _ treePart: TreePart ) {
self.wrappedTreePart = treePart
}
// MARK: Codable
enum CodingKeys: String, CodingKey {
case trunk,
branch,
apple
}
required convenience init( from decoder: Decoder ) throws {
let container = try decoder.container( keyedBy: CodingKeys.self )
var treePart: TreePart?
if let trunk = try container.decodeIfPresent( Trunk.self, forKey: .trunk ) {
treePart = trunk
}
if let branch = try container.decodeIfPresent( Branch.self, forKey: .branch ) {
treePart = branch
}
if let apple = try container.decodeIfPresent( Apple.self, forKey: .apple ) {
treePart = apple
}
guard let foundTreePart = treePart else {
let context = DecodingError.Context( codingPath: [CodingKeys.trunk, CodingKeys.branch, CodingKeys.apple], debugDescription: "Could not find the treePart key" )
throw DecodingError.keyNotFound( CodingKeys.trunk, context )
}
self.init( foundTreePart )
}
func encode( to encoder: Encoder ) throws {
var container = encoder.container( keyedBy: CodingKeys.self )
switch self.wrappedTreePart {
case let trunk as Trunk:
try container.encode( trunk, forKey: .trunk )
case let branch as Branch:
try container.encode( branch, forKey: .branch )
case let apple as Apple:
try container.encode( apple, forKey: .apple )
default:
fatalError( "Encoding error: No encoding implementation for \( type( of: self.wrappedTreePart ) )" )
}
}
}
extension AnyTreePart: Equatable {
static func ==( lhs: AnyTreePart, rhs: AnyTreePart ) -> Bool {
return lhs.wrappedTreePart.isEqualTo( rhs.wrappedTreePart )
}
}
///////////// TreePartNodeBase -> implemented by TreePartNode<T: TreePart> and AnyTreePartNode
protocol TreePartNodeBase: class {
var treePart: AnyTreePart { get set }
var uuid: UUID { get }
var parent: AnyTreePartNode? { get set }
var weakChildren: NSPointerArray { get }
func isEqualTo( _ other: TreePartNodeBase ) -> Bool
func asEquatable() -> AnyTreePartNode
}
extension TreePartNodeBase where Self: Equatable {
func isEqualTo( _ other: TreePartNodeBase ) -> Bool {
guard let otherTreePartNode = other as? Self else { return false }
return self == otherTreePartNode &&
self.treePart == other.treePart &&
self.uuid == other.uuid &&
self.parent == other.parent &&
self.children == other.children
}
func asEquatable() -> AnyTreePartNode {
return AnyTreePartNode( self )
}
}
extension TreePartNodeBase {
var children: [AnyTreePartNode] {
guard let allNodes = self.weakChildren.allObjects as? [AnyTreePartNode] else {
fatalError( "The children nodes are not of type \( type( of: AnyTreePartNode.self ) )" )
}
return allNodes
}
}
///////////// AnyTreePartNode -> wrapper of TreePartNode<T: TreePart>
class AnyTreePartNode: TreePartNodeBase, Codable {
unowned var wrappedTreePartNode: TreePartNodeBase
var treePart: AnyTreePart {
get {
return self.wrappedTreePartNode.treePart
}
set {
self.wrappedTreePartNode.treePart = newValue
}
}
var uuid: UUID {
return self.wrappedTreePartNode.uuid
}
/// The parent node
weak var parent: AnyTreePartNode? {
get {
return self.wrappedTreePartNode.parent
}
set {
self.wrappedTreePartNode.parent = newValue
}
}
/// The weak references to the children of this node
var weakChildren: NSPointerArray {
return self.wrappedTreePartNode.weakChildren
}
init( _ treePartNode: TreePartNodeBase ) {
self.wrappedTreePartNode = treePartNode
}
// MARK: Codable
enum CodingKeys: String, CodingKey {
case trunkNode,
branchNode,
appleNode
}
required convenience init( from decoder: Decoder ) throws {
let container = try decoder.container( keyedBy: CodingKeys.self )
// even if an empty Trunk is created, the decoder crashes
self.init( TreePartNode<Trunk>( Trunk() ) )
// This attempt of decoding possible nodes doesn't work
/*
if let trunkNode: TreePartNode<Trunk> = try container
.decodeIfPresent( TreePartNode<Trunk>.self, forKey: .trunkNode ) {
self.init( trunkNode )
} else if let branchNode: TreePartNode<Branch> = try container
.decodeIfPresent( TreePartNode<Branch>.self, forKey: .branchNode ) {
self.init( branchNode )
} else if let appleNode: TreePartNode<Apple> = try cont«ainer
.decodeIfPresent( TreePartNode<Apple>.self, forKey: .appleNode ) {
self.init( appleNode )
} else {
let context = DecodingError.Context( codingPath: [CodingKeys.trunkNode,
CodingKeys.branchNode,
CodingKeys.appleNode],
debugDescription: "Could not find the treePart node key" )
throw DecodingError.keyNotFound( CodingKeys.trunkNode, context )
}
*/
// TODO recreating the connections between the nodes should happen after all objects are decoded and will be done based on the UUIDs
}
func encode( to encoder: Encoder ) throws {
var container = encoder.container( keyedBy: CodingKeys.self )
switch self.wrappedTreePartNode {
case let trunkNode as TreePartNode<Trunk>:
try container.encode( trunkNode, forKey: .trunkNode )
case let branchNode as TreePartNode<Branch>:
try container.encode( branchNode, forKey: .branchNode )
case let appleNode as TreePartNode<Apple>:
try container.encode( appleNode, forKey: .appleNode )
default:
fatalError( "Encoding error: No encoding implementation for \( type( of: self.wrappedTreePartNode ) )" )
}
}
}
extension AnyTreePartNode: Equatable {
static func ==( lhs: AnyTreePartNode, rhs: AnyTreePartNode ) -> Bool {
return lhs.wrappedTreePartNode.isEqualTo( rhs.wrappedTreePartNode )
}
}
// enables printing of the wrapped tree part and its child elements
extension AnyTreePartNode: CustomStringConvertible {
var description: String {
var text = "\( type( of: self.wrappedTreePartNode.treePart.wrappedTreePart ))"
if !self.children.isEmpty {
text += " { " + self.children.map { [=12=].description }.joined( separator: ", " ) + " }"
}
return text
}
}
///////////// TreeParts (Trunk, Branch and Apple)
class Trunk: TreePart, Codable, Equatable {
var name: String
var color: String
init( name: String = "trunk",
color: String = "#CCC" ) {
self.name = name
self.color = color
}
static func ==(lhs: Trunk, rhs: Trunk) -> Bool {
return lhs.name == rhs.name &&
lhs.color == rhs.color
}
}
class Branch: TreePart, Codable, Equatable {
var name: String
var length: Int
init( name: String = "branch",
length: Int = 4 ) {
self.name = name
self.length = length
}
static func ==(lhs: Branch, rhs: Branch) -> Bool {
return lhs.name == rhs.name &&
lhs.length == rhs.length
}
}
class Apple: TreePart, Codable, Equatable {
var name: String
var size: Int
init( name: String = "apple",
size: Int = 2 ) {
self.name = name
self.size = size
}
static func ==(lhs: Apple, rhs: Apple) -> Bool {
return lhs.name == rhs.name &&
lhs.size == rhs.size
}
}
///////////// TreePartNode -> The node in the tree that contains the TreePart
class TreePartNode<T: TreePart>: TreePartNodeBase, Codable {
var equatableSelf: AnyTreePartNode!
var uuid: UUID
var treePart: AnyTreePart
var weakChildren = NSPointerArray.weakObjects()
private var parentUuid : UUID?
private var childrenUuids : [UUID]?
weak var parent: AnyTreePartNode? {
willSet {
if newValue == nil {
// unrelated code
// ... removes the references to this object in the parent node, if it exists
}
}
}
init( _ treePart: AnyTreePart,
uuid: UUID = UUID() ) {
self.treePart = treePart
self.uuid = uuid
self.equatableSelf = self.asEquatable()
}
convenience init( _ treePart: T,
uuid: UUID = UUID() ) {
self.init( treePart.asEquatable(),
uuid: uuid )
}
init( _ treePart: AnyTreePart,
uuid: UUID,
parentUuid: UUID?,
childrenUuids: [UUID]?) {
self.treePart = treePart
self.uuid = uuid
self.parentUuid = parentUuid
self.childrenUuids = childrenUuids
self.equatableSelf = self.asEquatable()
}
private func add( child: AnyTreePartNode ) {
child.parent = self.equatableSelf
self.weakChildren.addObject( child )
}
private func set( parent: AnyTreePartNode ) {
self.parent = parent
parent.weakChildren.addObject( self.equatableSelf )
}
// MARK: Codable
enum CodingKeys: String, CodingKey {
case treePart,
uuid,
parent,
children,
parentPort
}
required convenience init( from decoder: Decoder ) throws {
let container = try decoder.container( keyedBy: CodingKeys.self )
// non-optional values
let uuid: UUID = try container.decode( UUID.self, forKey: .uuid )
let treePart: AnyTreePart = try container.decode( AnyTreePart.self, forKey: .treePart )
// optional values
let childrenUuids: [UUID]? = try container.decodeIfPresent( [UUID].self, forKey: .children )
let parentUuid: UUID? = try container.decodeIfPresent( UUID.self, forKey: .parent )
self.init( treePart,
uuid: uuid,
parentUuid: parentUuid,
childrenUuids: childrenUuids)
}
func encode( to encoder: Encoder ) throws {
var container = encoder.container( keyedBy: CodingKeys.self )
// non-optional values
try container.encode( self.treePart, forKey: .treePart )
try container.encode( self.uuid, forKey: .uuid )
// optional values
if !self.children.isEmpty {
try container.encode( self.children.map { [=12=].uuid }, forKey: .children )
}
try container.encodeIfPresent( self.parent?.uuid, forKey: .parent )
}
}
extension TreePartNode: Equatable {
static func ==( lhs: TreePartNode, rhs: TreePartNode ) -> Bool {
return lhs.treePart == rhs.treePart &&
lhs.parent == rhs.parent &&
lhs.children == rhs.children
}
}
// enables printing of the wrapped tree part and its child elements
extension TreePartNode: CustomStringConvertible {
var description: String {
var text = "\( type( of: self.treePart.wrappedTreePart ))"
if !self.children.isEmpty {
text += " { " + self.children.map { [=12=].description }.joined( separator: ", " ) + " }"
}
return text
}
}
// MARK: functions for adding connections to other TreeParts for each specific TreePart type
extension TreePartNode where T: Trunk {
func add( child branch: TreePartNode<Branch> ) {
self.add( child: branch.equatableSelf )
}
}
extension TreePartNode where T: Branch {
func add( child apple: TreePartNode<Apple> ) {
self.add( child: apple.equatableSelf )
}
func add( child branch: TreePartNode<Branch> ) {
self.add( child: branch.equatableSelf )
}
func set( parent branch: TreePartNode<Branch> ) {
self.set( parent: branch.equatableSelf )
}
func set( parent trunk: TreePartNode<Trunk> ) {
self.set( parent: trunk.equatableSelf )
}
}
extension TreePartNode where T: Apple {
func set( parent branch: TreePartNode<Branch> ) {
self.set( parent: branch.equatableSelf )
}
}
////////////// Helper
extension NSPointerArray {
func addObject( _ object: AnyObject? ) {
guard let strongObject = object else { return }
let pointer = Unmanaged.passUnretained( strongObject ).toOpaque()
self.addPointer( pointer )
}
}
////////////// Test (The actual usage of the implementation above)
let trunk = Trunk()
let branch1 = Branch()
let branch2 = Branch()
let branch3 = Branch()
let apple1 = Apple()
let apple2 = Apple()
let trunkNode = TreePartNode<Trunk>( trunk )
let branchNode1 = TreePartNode<Branch>( branch1 )
let branchNode2 = TreePartNode<Branch>( branch2 )
let branchNode3 = TreePartNode<Branch>( branch3 )
let appleNode1 = TreePartNode<Apple>( apple1 )
let appleNode2 = TreePartNode<Apple>( apple2 )
trunkNode.add( child: branchNode1 )
trunkNode.add( child: branchNode2 )
branchNode2.add( child: branchNode3 )
branchNode1.add( child: appleNode1 )
branchNode3.add( child: appleNode2 )
let tree = [trunkNode.equatableSelf,
branchNode1.equatableSelf,
branchNode2.equatableSelf,
branchNode3.equatableSelf,
appleNode1.equatableSelf,
appleNode2.equatableSelf]
print( "expected result when printing the decoded trunk node: \(trunkNode)" )
let encoder = JSONEncoder()
let decoder = JSONDecoder()
encoder.outputFormatting = [.prettyPrinted, .sortedKeys]
// This is how the encoded tree looks like
let jsonTree = """
[
{
"trunkNode" : {
"children" : [
"399B35A7-3307-4EF6-8B4C-1B83A8F734CD",
"60582654-13B9-40D0-8275-3C6649614069"
],
"treePart" : {
"trunk" : {
"color" : "#CCC",
"name" : "trunk"
}
},
"uuid" : "55748AEB-271E-4560-9EE8-F00C670C8896"
}
},
{
"branchNode" : {
"children" : [
"0349C0DF-FE58-4D8E-AA72-7466749EB1D6"
],
"parent" : "55748AEB-271E-4560-9EE8-F00C670C8896",
"treePart" : {
"branch" : {
"length" : 4,
"name" : "branch"
}
},
"uuid" : "399B35A7-3307-4EF6-8B4C-1B83A8F734CD"
}
},
{
"branchNode" : {
"children" : [
"6DB14BD5-3E4A-40C4-8EBF-FBD3CC6050C7"
],
"parent" : "55748AEB-271E-4560-9EE8-F00C670C8896",
"treePart" : {
"branch" : {
"length" : 4,
"name" : "branch"
}
},
"uuid" : "60582654-13B9-40D0-8275-3C6649614069"
}
},
{
"branchNode" : {
"children" : [
"9FCCDBF6-27A7-4E21-8681-5F3E63330504"
],
"parent" : "60582654-13B9-40D0-8275-3C6649614069",
"treePart" : {
"branch" : {
"length" : 4,
"name" : "branch"
}
},
"uuid" : "6DB14BD5-3E4A-40C4-8EBF-FBD3CC6050C7"
}
},
{
"appleNode" : {
"parent" : "399B35A7-3307-4EF6-8B4C-1B83A8F734CD",
"treePart" : {
"apple" : {
"name" : "apple",
"size" : 2
}
},
"uuid" : "0349C0DF-FE58-4D8E-AA72-7466749EB1D6"
}
},
{
"appleNode" : {
"parent" : "6DB14BD5-3E4A-40C4-8EBF-FBD3CC6050C7",
"treePart" : {
"apple" : {
"name" : "apple",
"size" : 2
}
},
"uuid" : "9FCCDBF6-27A7-4E21-8681-5F3E63330504"
}
}
]
""".data(using: .utf8)!
do {
print( "begin decoding" )
/* This currently produces an error: Playground execution aborted: error: Execution was interrupted, reason: signal SIGABRT. The process has been left at the point where it was interrupted, use "thread return -x" to return to the state before expression evaluation.
let decodedTree = try decoder.decode( [AnyTreePartNode].self, from: jsonTree )
print( decodedTree.first( where: { [=12=].wrappedTreePartNode.treePart.wrappedTreePart is Trunk } )! )
*/
} catch let error {
print( error )
}
AnyTreePartNode 中的解码函数应该如何解码 JSON？我错过了什么？
我有变化只是从 unowned var wrappedTreePartNode: TreePartNodeBase 行删除 unowned
并编译了相同的代码。
结果：
打印解码后的中继节点时的预期结果：Trunk { Branch { Apple }, Branch { Branch { Apple } } }
开始解码
[树干，树枝，树枝，树枝，苹果，苹果]
代码：
//
// ViewController.swift
// TestDrive
//
// Created by Mahipal on 25/04/18.
// Copyright © 2018 Vandana. All rights reserved.
//
import UIKit
class ViewController: UIViewController {
override func viewDidLoad() {
super.viewDidLoad()
// Do any additional setup after loading the view, typically from a nib.
////////////// Test (The actual usage of the implementation above)
let trunk = Trunk()
let branch1 = Branch()
let branch2 = Branch()
let branch3 = Branch()
let apple1 = Apple()
let apple2 = Apple()
let trunkNode = TreePartNode<Trunk>( trunk )
let branchNode1 = TreePartNode<Branch>( branch1 )
let branchNode2 = TreePartNode<Branch>( branch2 )
let branchNode3 = TreePartNode<Branch>( branch3 )
let appleNode1 = TreePartNode<Apple>( apple1 )
let appleNode2 = TreePartNode<Apple>( apple2 )
trunkNode.add( child: branchNode1 )
trunkNode.add( child: branchNode2 )
branchNode2.add( child: branchNode3 )
branchNode1.add( child: appleNode1 )
branchNode3.add( child: appleNode2 )
let tree = [trunkNode.equatableSelf,
branchNode1.equatableSelf,
branchNode2.equatableSelf,
branchNode3.equatableSelf,
appleNode1.equatableSelf,
appleNode2.equatableSelf]
print( "expected result when printing the decoded trunk node: \(trunkNode)" )
let encoder = JSONEncoder()
let decoder = JSONDecoder()
encoder.outputFormatting = [.prettyPrinted, .sortedKeys]
// This is how the encoded tree looks like
let jsonTree = """
[
{
"trunkNode" : {
"children" : [
"399B35A7-3307-4EF6-8B4C-1B83A8F734CD",
"60582654-13B9-40D0-8275-3C6649614069"
],
"treePart" : {
"trunk" : {
"color" : "#CCC",
"name" : "trunk"
}
},
"uuid" : "55748AEB-271E-4560-9EE8-F00C670C8896"
}
},
{
"branchNode" : {
"children" : [
"0349C0DF-FE58-4D8E-AA72-7466749EB1D6"
],
"parent" : "55748AEB-271E-4560-9EE8-F00C670C8896",
"treePart" : {
"branch" : {
"length" : 4,
"name" : "branch"
}
},
"uuid" : "399B35A7-3307-4EF6-8B4C-1B83A8F734CD"
}
},
{
"branchNode" : {
"children" : [
"6DB14BD5-3E4A-40C4-8EBF-FBD3CC6050C7"
],
"parent" : "55748AEB-271E-4560-9EE8-F00C670C8896",
"treePart" : {
"branch" : {
"length" : 4,
"name" : "branch"
}
},
"uuid" : "60582654-13B9-40D0-8275-3C6649614069"
}
},
{
"branchNode" : {
"children" : [
"9FCCDBF6-27A7-4E21-8681-5F3E63330504"
],
"parent" : "60582654-13B9-40D0-8275-3C6649614069",
"treePart" : {
"branch" : {
"length" : 4,
"name" : "branch"
}
},
"uuid" : "6DB14BD5-3E4A-40C4-8EBF-FBD3CC6050C7"
}
},
{
"appleNode" : {
"parent" : "399B35A7-3307-4EF6-8B4C-1B83A8F734CD",
"treePart" : {
"apple" : {
"name" : "apple",
"size" : 2
}
},
"uuid" : "0349C0DF-FE58-4D8E-AA72-7466749EB1D6"
}
},
{
"appleNode" : {
"parent" : "6DB14BD5-3E4A-40C4-8EBF-FBD3CC6050C7",
"treePart" : {
"apple" : {
"name" : "apple",
"size" : 2
}
},
"uuid" : "9FCCDBF6-27A7-4E21-8681-5F3E63330504"
}
}
]
""".data(using: .utf8)!
do {
print( "begin decoding" )
// This currently produces an error: Playground execution aborted: error: Execution was interrupted, reason: signal SIGABRT. The process has been left at the point where it was interrupted, use "thread return -x" to return to the state before expression evaluation.
let decodedTree = try decoder.decode( [AnyTreePartNode].self, from: jsonTree )
print( decodedTree )
} catch let error {
print( error )
}
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
// Dispose of any resources that can be recreated.
}
}
import Foundation
///////////// TreePart -> implemented by Trunk, Branch, Apple and AnyTreePart
protocol TreePart: Codable {
var name: String { get set }
func isEqualTo( _ other: TreePart ) -> Bool
func asEquatable() -> AnyTreePart
}
extension TreePart where Self: Equatable {
func isEqualTo( _ other: TreePart ) -> Bool {
guard let otherTreePart = other as? Self else { return false }
return self == otherTreePart
}
func asEquatable() -> AnyTreePart {
return AnyTreePart( self )
}
}
///////////// AnyTreePart -> wrapper for Trunk, Branch and Apple
class AnyTreePart: TreePart, Codable {
var wrappedTreePart: TreePart
var name: String {
get {
return self.wrappedTreePart.name
}
set {
self.wrappedTreePart.name = newValue
}
}
init( _ treePart: TreePart ) {
self.wrappedTreePart = treePart
}
// MARK: Codable
enum CodingKeys: String, CodingKey {
case trunk,
branch,
apple
}
required convenience init( from decoder: Decoder ) throws {
let container = try decoder.container( keyedBy: CodingKeys.self )
var treePart: TreePart?
if let trunk = try container.decodeIfPresent( Trunk.self, forKey: .trunk ) {
treePart = trunk
}
if let branch = try container.decodeIfPresent( Branch.self, forKey: .branch ) {
treePart = branch
}
if let apple = try container.decodeIfPresent( Apple.self, forKey: .apple ) {
treePart = apple
}
guard let foundTreePart = treePart else {
let context = DecodingError.Context( codingPath: [CodingKeys.trunk, CodingKeys.branch, CodingKeys.apple], debugDescription: "Could not find the treePart key" )
throw DecodingError.keyNotFound( CodingKeys.trunk, context )
}
self.init( foundTreePart )
}
func encode( to encoder: Encoder ) throws {
var container = encoder.container( keyedBy: CodingKeys.self )
switch self.wrappedTreePart {
case let trunk as Trunk:
try container.encode( trunk, forKey: .trunk )
case let branch as Branch:
try container.encode( branch, forKey: .branch )
case let apple as Apple:
try container.encode( apple, forKey: .apple )
default:
fatalError( "Encoding error: No encoding implementation for \( type( of: self.wrappedTreePart ) )" )
}
}
}
extension AnyTreePart: Equatable {
static func ==( lhs: AnyTreePart, rhs: AnyTreePart ) -> Bool {
return lhs.wrappedTreePart.isEqualTo( rhs.wrappedTreePart )
}
}
///////////// TreePartNodeBase -> implemented by TreePartNode<T: TreePart> and AnyTreePartNode
protocol TreePartNodeBase: class {
var treePart: AnyTreePart { get set }
var uuid: UUID { get }
var parent: AnyTreePartNode? { get set }
var weakChildren: NSPointerArray { get }
func isEqualTo( _ other: TreePartNodeBase ) -> Bool
func asEquatable() -> AnyTreePartNode
}
extension TreePartNodeBase where Self: Equatable {
func isEqualTo( _ other: TreePartNodeBase ) -> Bool {
guard let otherTreePartNode = other as? Self else { return false }
return self == otherTreePartNode &&
self.treePart == other.treePart &&
self.uuid == other.uuid &&
self.parent == other.parent &&
self.children == other.children
}
func asEquatable() -> AnyTreePartNode {
return AnyTreePartNode( self )
}
}
extension TreePartNodeBase {
var children: [AnyTreePartNode] {
guard let allNodes = self.weakChildren.allObjects as? [AnyTreePartNode] else {
fatalError( "The children nodes are not of type \( type( of: AnyTreePartNode.self ) )" )
}
return allNodes
}
}
///////////// AnyTreePartNode -> wrapper of TreePartNode<T: TreePart>
class AnyTreePartNode: TreePartNodeBase, Codable {
var wrappedTreePartNode: TreePartNodeBase
var treePart: AnyTreePart {
get {
return self.wrappedTreePartNode.treePart
}
set {
self.wrappedTreePartNode.treePart = newValue
}
}
var uuid: UUID {
return self.wrappedTreePartNode.uuid
}
/// The parent node
weak var parent: AnyTreePartNode? {
get {
return self.wrappedTreePartNode.parent
}
set {
self.wrappedTreePartNode.parent = newValue
}
}
/// The weak references to the children of this node
var weakChildren: NSPointerArray {
return self.wrappedTreePartNode.weakChildren
}
init( _ treePartNode: TreePartNodeBase ) {
self.wrappedTreePartNode = treePartNode
}
// MARK: Codable
enum CodingKeys: String, CodingKey {
case trunkNode,
branchNode,
appleNode
}
required convenience init( from decoder: Decoder ) throws {
let container = try decoder.container( keyedBy: CodingKeys.self)
// This attempt of decoding possible nodes doesn't work
if let trunkNode: TreePartNode<Trunk> = try container.decodeIfPresent( TreePartNode<Trunk>.self, forKey: .trunkNode ) {
self.init( trunkNode )
} else if let branchNode: TreePartNode<Branch> = try container
.decodeIfPresent( TreePartNode<Branch>.self, forKey: .branchNode ) {
self.init( branchNode )
} else if let appleNode: TreePartNode<Apple> = try container
.decodeIfPresent( TreePartNode<Apple>.self, forKey: .appleNode ) {
self.init( appleNode )
} else {
let context = DecodingError.Context( codingPath: [CodingKeys.trunkNode,
CodingKeys.branchNode,
CodingKeys.appleNode],
debugDescription: "Could not find the treePart node key" )
throw DecodingError.keyNotFound( CodingKeys.trunkNode, context )
}
// TODO recreating the connections between the nodes should happen after all objects are decoded and will be done based on the UUIDs
}
func encode( to encoder: Encoder ) throws {
var container = encoder.container( keyedBy: CodingKeys.self )
switch self.wrappedTreePartNode {
case let trunkNode as TreePartNode<Trunk>:
try container.encode( trunkNode, forKey: .trunkNode )
case let branchNode as TreePartNode<Branch>:
try container.encode( branchNode, forKey: .branchNode )
case let appleNode as TreePartNode<Apple>:
try container.encode( appleNode, forKey: .appleNode )
default:
fatalError( "Encoding error: No encoding implementation for \( type( of: self.wrappedTreePartNode ) )" )
}
}
}
extension AnyTreePartNode: Equatable {
static func ==( lhs: AnyTreePartNode, rhs: AnyTreePartNode ) -> Bool {
return lhs.wrappedTreePartNode.isEqualTo( rhs.wrappedTreePartNode )
}
}
// enables printing of the wrapped tree part and its child elements
extension AnyTreePartNode: CustomStringConvertible {
var description: String {
var text = "\( type( of: self.wrappedTreePartNode.treePart.wrappedTreePart ))"
if !self.children.isEmpty {
text += " { " + self.children.map { [=10=].description }.joined( separator: ", " ) + " }"
}
return text
}
}
///////////// TreeParts (Trunk, Branch and Apple)
class Trunk: TreePart, Codable, Equatable {
var name: String
var color: String
init( name: String = "trunk",
color: String = "#CCC" ) {
self.name = name
self.color = color
}
static func ==(lhs: Trunk, rhs: Trunk) -> Bool {
return lhs.name == rhs.name &&
lhs.color == rhs.color
}
}
class Branch: TreePart, Codable, Equatable {
var name: String
var length: Int
init( name: String = "branch",
length: Int = 4 ) {
self.name = name
self.length = length
}
static func ==(lhs: Branch, rhs: Branch) -> Bool {
return lhs.name == rhs.name &&
lhs.length == rhs.length
}
}
class Apple: TreePart, Codable, Equatable {
var name: String
var size: Int
init( name: String = "apple",
size: Int = 2 ) {
self.name = name
self.size = size
}
static func ==(lhs: Apple, rhs: Apple) -> Bool {
return lhs.name == rhs.name &&
lhs.size == rhs.size
}
}
///////////// TreePartNode -> The node in the tree that contains the TreePart
class TreePartNode<T: TreePart>: TreePartNodeBase, Codable {
var equatableSelf: AnyTreePartNode!
var uuid: UUID
var treePart: AnyTreePart
var weakChildren = NSPointerArray.weakObjects()
private var parentUuid : UUID?
private var childrenUuids : [UUID]?
weak var parent: AnyTreePartNode? {
willSet {
if newValue == nil {
// unrelated code
// ... removes the references to this object in the parent node, if it exists
}
}
}
init( _ treePart: AnyTreePart,
uuid: UUID = UUID() ) {
self.treePart = treePart
self.uuid = uuid
self.equatableSelf = self.asEquatable()
}
convenience init( _ treePart: T,
uuid: UUID = UUID() ) {
self.init( treePart.asEquatable(),
uuid: uuid )
}
init( _ treePart: AnyTreePart,
uuid: UUID,
parentUuid: UUID?,
childrenUuids: [UUID]?) {
self.treePart = treePart
self.uuid = uuid
self.parentUuid = parentUuid
self.childrenUuids = childrenUuids
self.equatableSelf = self.asEquatable()
}
private func add( child: AnyTreePartNode ) {
child.parent = self.equatableSelf
self.weakChildren.addObject( child )
}
private func set( parent: AnyTreePartNode ) {
self.parent = parent
parent.weakChildren.addObject( self.equatableSelf )
}
// MARK: Codable
enum CodingKeys: String, CodingKey {
case treePart,
uuid,
parent,
children,
parentPort
}
required convenience init( from decoder: Decoder ) throws {
let container = try decoder.container( keyedBy: CodingKeys.self )
// non-optional values
let uuid: UUID = try container.decode( UUID.self, forKey: .uuid )
let treePart: AnyTreePart = try container.decode( AnyTreePart.self, forKey: .treePart )
// optional values
let childrenUuids: [UUID]? = try container.decodeIfPresent( [UUID].self, forKey: .children )
let parentUuid: UUID? = try container.decodeIfPresent( UUID.self, forKey: .parent )
self.init( treePart,
uuid: uuid,
parentUuid: parentUuid,
childrenUuids: childrenUuids)
}
func encode( to encoder: Encoder ) throws {
var container = encoder.container( keyedBy: CodingKeys.self )
// non-optional values
try container.encode( self.treePart, forKey: .treePart )
try container.encode( self.uuid, forKey: .uuid )
// optional values
if !self.children.isEmpty {
try container.encode( self.children.map { [=10=].uuid }, forKey: .children )
}
try container.encodeIfPresent( self.parent?.uuid, forKey: .parent )
}
}
extension TreePartNode: Equatable {
static func ==( lhs: TreePartNode, rhs: TreePartNode ) -> Bool {
return lhs.treePart == rhs.treePart &&
lhs.parent == rhs.parent &&
lhs.children == rhs.children
}
}
// enables printing of the wrapped tree part and its child elements
extension TreePartNode: CustomStringConvertible {
var description: String {
var text = "\( type( of: self.treePart.wrappedTreePart ))"
if !self.children.isEmpty {
text += " { " + self.children.map { [=10=].description }.joined( separator: ", " ) + " }"
}
return text
}
}
// MARK: functions for adding connections to other TreeParts for each specific TreePart type
extension TreePartNode where T: Trunk {
func add( child branch: TreePartNode<Branch> ) {
self.add( child: branch.equatableSelf )
}
}
extension TreePartNode where T: Branch {
func add( child apple: TreePartNode<Apple> ) {
self.add( child: apple.equatableSelf )
}
func add( child branch: TreePartNode<Branch> ) {
self.add( child: branch.equatableSelf )
}
func set( parent branch: TreePartNode<Branch> ) {
self.set( parent: branch.equatableSelf )
}
func set( parent trunk: TreePartNode<Trunk> ) {
self.set( parent: trunk.equatableSelf )
}
}
extension TreePartNode where T: Apple {
func set( parent branch: TreePartNode<Branch> ) {
self.set( parent: branch.equatableSelf )
}
}
////////////// Helper
extension NSPointerArray {
func addObject( _ object: AnyObject? ) {
guard let strongObject = object else { return }
let pointer = Unmanaged.passUnretained( strongObject ).toOpaque()
self.addPointer( pointer )
}
}
目标
我需要以树状方式互连的通用对象的表示。这棵树及其对象应具有以下特征：
- 应该可以用 3 个部分构建一棵树：trunk、branch 和 apple
- 无法将父级添加到 trunk
- 其中一个trunk只能获取多个branch节点作为子元素
- 其中一个 branch 只能有多个 apple 节点作为子元素
- 其中 branch 只能有 trunk 或 branch[= 类型的父级84=]
- 无法将子元素添加到 apple
- 检查有效配置应该在编译时>>使用泛型
- 它应该可以通过实现
Codable协议来编码- 所以可以编码成JSON
- 并从 JSON 解码
作为这个问题末尾的一个例子，我创建了一个满足所有要求但只有一个要求的游乐场： 从 JSON
解码树示例代码的解释
一棵树由节点组成，在本例中为 TreePartNodes，它们正在实施 TreePartNodeBase 协议。
此示例中的树是一个 AnyTreePartNode 数组，它们也实现了 TreePartNodeBase 协议并包装了一个实现 TreePartNodeBase 协议的对象，该协议应该是通用的 TreePartNode (TreePartNode<Trunk>、TreePartNode<Branch> 或 TreePartNode<Apple>).
A TreePartNode 具有类型 AnyTreePart 的 属性 treePart。 AnyTreePart（类似于AnyTreePartNode）包装一个实现了TreePart协议（Trunk、Branch或Apple）的对象。
所有这些 类 都在实施 Codable 和 Equatable。
代码已准备好粘贴到 Xcode 游乐场
import Foundation
///////////// TreePart -> implemented by Trunk, Branch, Apple and AnyTreePart
protocol TreePart: Codable {
var name: String { get set }
func isEqualTo( _ other: TreePart ) -> Bool
func asEquatable() -> AnyTreePart
}
extension TreePart where Self: Equatable {
func isEqualTo( _ other: TreePart ) -> Bool {
guard let otherTreePart = other as? Self else { return false }
return self == otherTreePart
}
func asEquatable() -> AnyTreePart {
return AnyTreePart( self )
}
}
///////////// AnyTreePart -> wrapper for Trunk, Branch and Apple
class AnyTreePart: TreePart, Codable {
var wrappedTreePart: TreePart
var name: String {
get {
return self.wrappedTreePart.name
}
set {
self.wrappedTreePart.name = newValue
}
}
init( _ treePart: TreePart ) {
self.wrappedTreePart = treePart
}
// MARK: Codable
enum CodingKeys: String, CodingKey {
case trunk,
branch,
apple
}
required convenience init( from decoder: Decoder ) throws {
let container = try decoder.container( keyedBy: CodingKeys.self )
var treePart: TreePart?
if let trunk = try container.decodeIfPresent( Trunk.self, forKey: .trunk ) {
treePart = trunk
}
if let branch = try container.decodeIfPresent( Branch.self, forKey: .branch ) {
treePart = branch
}
if let apple = try container.decodeIfPresent( Apple.self, forKey: .apple ) {
treePart = apple
}
guard let foundTreePart = treePart else {
let context = DecodingError.Context( codingPath: [CodingKeys.trunk, CodingKeys.branch, CodingKeys.apple], debugDescription: "Could not find the treePart key" )
throw DecodingError.keyNotFound( CodingKeys.trunk, context )
}
self.init( foundTreePart )
}
func encode( to encoder: Encoder ) throws {
var container = encoder.container( keyedBy: CodingKeys.self )
switch self.wrappedTreePart {
case let trunk as Trunk:
try container.encode( trunk, forKey: .trunk )
case let branch as Branch:
try container.encode( branch, forKey: .branch )
case let apple as Apple:
try container.encode( apple, forKey: .apple )
default:
fatalError( "Encoding error: No encoding implementation for \( type( of: self.wrappedTreePart ) )" )
}
}
}
extension AnyTreePart: Equatable {
static func ==( lhs: AnyTreePart, rhs: AnyTreePart ) -> Bool {
return lhs.wrappedTreePart.isEqualTo( rhs.wrappedTreePart )
}
}
///////////// TreePartNodeBase -> implemented by TreePartNode<T: TreePart> and AnyTreePartNode
protocol TreePartNodeBase: class {
var treePart: AnyTreePart { get set }
var uuid: UUID { get }
var parent: AnyTreePartNode? { get set }
var weakChildren: NSPointerArray { get }
func isEqualTo( _ other: TreePartNodeBase ) -> Bool
func asEquatable() -> AnyTreePartNode
}
extension TreePartNodeBase where Self: Equatable {
func isEqualTo( _ other: TreePartNodeBase ) -> Bool {
guard let otherTreePartNode = other as? Self else { return false }
return self == otherTreePartNode &&
self.treePart == other.treePart &&
self.uuid == other.uuid &&
self.parent == other.parent &&
self.children == other.children
}
func asEquatable() -> AnyTreePartNode {
return AnyTreePartNode( self )
}
}
extension TreePartNodeBase {
var children: [AnyTreePartNode] {
guard let allNodes = self.weakChildren.allObjects as? [AnyTreePartNode] else {
fatalError( "The children nodes are not of type \( type( of: AnyTreePartNode.self ) )" )
}
return allNodes
}
}
///////////// AnyTreePartNode -> wrapper of TreePartNode<T: TreePart>
class AnyTreePartNode: TreePartNodeBase, Codable {
unowned var wrappedTreePartNode: TreePartNodeBase
var treePart: AnyTreePart {
get {
return self.wrappedTreePartNode.treePart
}
set {
self.wrappedTreePartNode.treePart = newValue
}
}
var uuid: UUID {
return self.wrappedTreePartNode.uuid
}
/// The parent node
weak var parent: AnyTreePartNode? {
get {
return self.wrappedTreePartNode.parent
}
set {
self.wrappedTreePartNode.parent = newValue
}
}
/// The weak references to the children of this node
var weakChildren: NSPointerArray {
return self.wrappedTreePartNode.weakChildren
}
init( _ treePartNode: TreePartNodeBase ) {
self.wrappedTreePartNode = treePartNode
}
// MARK: Codable
enum CodingKeys: String, CodingKey {
case trunkNode,
branchNode,
appleNode
}
required convenience init( from decoder: Decoder ) throws {
let container = try decoder.container( keyedBy: CodingKeys.self )
// even if an empty Trunk is created, the decoder crashes
self.init( TreePartNode<Trunk>( Trunk() ) )
// This attempt of decoding possible nodes doesn't work
/*
if let trunkNode: TreePartNode<Trunk> = try container
.decodeIfPresent( TreePartNode<Trunk>.self, forKey: .trunkNode ) {
self.init( trunkNode )
} else if let branchNode: TreePartNode<Branch> = try container
.decodeIfPresent( TreePartNode<Branch>.self, forKey: .branchNode ) {
self.init( branchNode )
} else if let appleNode: TreePartNode<Apple> = try cont«ainer
.decodeIfPresent( TreePartNode<Apple>.self, forKey: .appleNode ) {
self.init( appleNode )
} else {
let context = DecodingError.Context( codingPath: [CodingKeys.trunkNode,
CodingKeys.branchNode,
CodingKeys.appleNode],
debugDescription: "Could not find the treePart node key" )
throw DecodingError.keyNotFound( CodingKeys.trunkNode, context )
}
*/
// TODO recreating the connections between the nodes should happen after all objects are decoded and will be done based on the UUIDs
}
func encode( to encoder: Encoder ) throws {
var container = encoder.container( keyedBy: CodingKeys.self )
switch self.wrappedTreePartNode {
case let trunkNode as TreePartNode<Trunk>:
try container.encode( trunkNode, forKey: .trunkNode )
case let branchNode as TreePartNode<Branch>:
try container.encode( branchNode, forKey: .branchNode )
case let appleNode as TreePartNode<Apple>:
try container.encode( appleNode, forKey: .appleNode )
default:
fatalError( "Encoding error: No encoding implementation for \( type( of: self.wrappedTreePartNode ) )" )
}
}
}
extension AnyTreePartNode: Equatable {
static func ==( lhs: AnyTreePartNode, rhs: AnyTreePartNode ) -> Bool {
return lhs.wrappedTreePartNode.isEqualTo( rhs.wrappedTreePartNode )
}
}
// enables printing of the wrapped tree part and its child elements
extension AnyTreePartNode: CustomStringConvertible {
var description: String {
var text = "\( type( of: self.wrappedTreePartNode.treePart.wrappedTreePart ))"
if !self.children.isEmpty {
text += " { " + self.children.map { [=12=].description }.joined( separator: ", " ) + " }"
}
return text
}
}
///////////// TreeParts (Trunk, Branch and Apple)
class Trunk: TreePart, Codable, Equatable {
var name: String
var color: String
init( name: String = "trunk",
color: String = "#CCC" ) {
self.name = name
self.color = color
}
static func ==(lhs: Trunk, rhs: Trunk) -> Bool {
return lhs.name == rhs.name &&
lhs.color == rhs.color
}
}
class Branch: TreePart, Codable, Equatable {
var name: String
var length: Int
init( name: String = "branch",
length: Int = 4 ) {
self.name = name
self.length = length
}
static func ==(lhs: Branch, rhs: Branch) -> Bool {
return lhs.name == rhs.name &&
lhs.length == rhs.length
}
}
class Apple: TreePart, Codable, Equatable {
var name: String
var size: Int
init( name: String = "apple",
size: Int = 2 ) {
self.name = name
self.size = size
}
static func ==(lhs: Apple, rhs: Apple) -> Bool {
return lhs.name == rhs.name &&
lhs.size == rhs.size
}
}
///////////// TreePartNode -> The node in the tree that contains the TreePart
class TreePartNode<T: TreePart>: TreePartNodeBase, Codable {
var equatableSelf: AnyTreePartNode!
var uuid: UUID
var treePart: AnyTreePart
var weakChildren = NSPointerArray.weakObjects()
private var parentUuid : UUID?
private var childrenUuids : [UUID]?
weak var parent: AnyTreePartNode? {
willSet {
if newValue == nil {
// unrelated code
// ... removes the references to this object in the parent node, if it exists
}
}
}
init( _ treePart: AnyTreePart,
uuid: UUID = UUID() ) {
self.treePart = treePart
self.uuid = uuid
self.equatableSelf = self.asEquatable()
}
convenience init( _ treePart: T,
uuid: UUID = UUID() ) {
self.init( treePart.asEquatable(),
uuid: uuid )
}
init( _ treePart: AnyTreePart,
uuid: UUID,
parentUuid: UUID?,
childrenUuids: [UUID]?) {
self.treePart = treePart
self.uuid = uuid
self.parentUuid = parentUuid
self.childrenUuids = childrenUuids
self.equatableSelf = self.asEquatable()
}
private func add( child: AnyTreePartNode ) {
child.parent = self.equatableSelf
self.weakChildren.addObject( child )
}
private func set( parent: AnyTreePartNode ) {
self.parent = parent
parent.weakChildren.addObject( self.equatableSelf )
}
// MARK: Codable
enum CodingKeys: String, CodingKey {
case treePart,
uuid,
parent,
children,
parentPort
}
required convenience init( from decoder: Decoder ) throws {
let container = try decoder.container( keyedBy: CodingKeys.self )
// non-optional values
let uuid: UUID = try container.decode( UUID.self, forKey: .uuid )
let treePart: AnyTreePart = try container.decode( AnyTreePart.self, forKey: .treePart )
// optional values
let childrenUuids: [UUID]? = try container.decodeIfPresent( [UUID].self, forKey: .children )
let parentUuid: UUID? = try container.decodeIfPresent( UUID.self, forKey: .parent )
self.init( treePart,
uuid: uuid,
parentUuid: parentUuid,
childrenUuids: childrenUuids)
}
func encode( to encoder: Encoder ) throws {
var container = encoder.container( keyedBy: CodingKeys.self )
// non-optional values
try container.encode( self.treePart, forKey: .treePart )
try container.encode( self.uuid, forKey: .uuid )
// optional values
if !self.children.isEmpty {
try container.encode( self.children.map { [=12=].uuid }, forKey: .children )
}
try container.encodeIfPresent( self.parent?.uuid, forKey: .parent )
}
}
extension TreePartNode: Equatable {
static func ==( lhs: TreePartNode, rhs: TreePartNode ) -> Bool {
return lhs.treePart == rhs.treePart &&
lhs.parent == rhs.parent &&
lhs.children == rhs.children
}
}
// enables printing of the wrapped tree part and its child elements
extension TreePartNode: CustomStringConvertible {
var description: String {
var text = "\( type( of: self.treePart.wrappedTreePart ))"
if !self.children.isEmpty {
text += " { " + self.children.map { [=12=].description }.joined( separator: ", " ) + " }"
}
return text
}
}
// MARK: functions for adding connections to other TreeParts for each specific TreePart type
extension TreePartNode where T: Trunk {
func add( child branch: TreePartNode<Branch> ) {
self.add( child: branch.equatableSelf )
}
}
extension TreePartNode where T: Branch {
func add( child apple: TreePartNode<Apple> ) {
self.add( child: apple.equatableSelf )
}
func add( child branch: TreePartNode<Branch> ) {
self.add( child: branch.equatableSelf )
}
func set( parent branch: TreePartNode<Branch> ) {
self.set( parent: branch.equatableSelf )
}
func set( parent trunk: TreePartNode<Trunk> ) {
self.set( parent: trunk.equatableSelf )
}
}
extension TreePartNode where T: Apple {
func set( parent branch: TreePartNode<Branch> ) {
self.set( parent: branch.equatableSelf )
}
}
////////////// Helper
extension NSPointerArray {
func addObject( _ object: AnyObject? ) {
guard let strongObject = object else { return }
let pointer = Unmanaged.passUnretained( strongObject ).toOpaque()
self.addPointer( pointer )
}
}
////////////// Test (The actual usage of the implementation above)
let trunk = Trunk()
let branch1 = Branch()
let branch2 = Branch()
let branch3 = Branch()
let apple1 = Apple()
let apple2 = Apple()
let trunkNode = TreePartNode<Trunk>( trunk )
let branchNode1 = TreePartNode<Branch>( branch1 )
let branchNode2 = TreePartNode<Branch>( branch2 )
let branchNode3 = TreePartNode<Branch>( branch3 )
let appleNode1 = TreePartNode<Apple>( apple1 )
let appleNode2 = TreePartNode<Apple>( apple2 )
trunkNode.add( child: branchNode1 )
trunkNode.add( child: branchNode2 )
branchNode2.add( child: branchNode3 )
branchNode1.add( child: appleNode1 )
branchNode3.add( child: appleNode2 )
let tree = [trunkNode.equatableSelf,
branchNode1.equatableSelf,
branchNode2.equatableSelf,
branchNode3.equatableSelf,
appleNode1.equatableSelf,
appleNode2.equatableSelf]
print( "expected result when printing the decoded trunk node: \(trunkNode)" )
let encoder = JSONEncoder()
let decoder = JSONDecoder()
encoder.outputFormatting = [.prettyPrinted, .sortedKeys]
// This is how the encoded tree looks like
let jsonTree = """
[
{
"trunkNode" : {
"children" : [
"399B35A7-3307-4EF6-8B4C-1B83A8F734CD",
"60582654-13B9-40D0-8275-3C6649614069"
],
"treePart" : {
"trunk" : {
"color" : "#CCC",
"name" : "trunk"
}
},
"uuid" : "55748AEB-271E-4560-9EE8-F00C670C8896"
}
},
{
"branchNode" : {
"children" : [
"0349C0DF-FE58-4D8E-AA72-7466749EB1D6"
],
"parent" : "55748AEB-271E-4560-9EE8-F00C670C8896",
"treePart" : {
"branch" : {
"length" : 4,
"name" : "branch"
}
},
"uuid" : "399B35A7-3307-4EF6-8B4C-1B83A8F734CD"
}
},
{
"branchNode" : {
"children" : [
"6DB14BD5-3E4A-40C4-8EBF-FBD3CC6050C7"
],
"parent" : "55748AEB-271E-4560-9EE8-F00C670C8896",
"treePart" : {
"branch" : {
"length" : 4,
"name" : "branch"
}
},
"uuid" : "60582654-13B9-40D0-8275-3C6649614069"
}
},
{
"branchNode" : {
"children" : [
"9FCCDBF6-27A7-4E21-8681-5F3E63330504"
],
"parent" : "60582654-13B9-40D0-8275-3C6649614069",
"treePart" : {
"branch" : {
"length" : 4,
"name" : "branch"
}
},
"uuid" : "6DB14BD5-3E4A-40C4-8EBF-FBD3CC6050C7"
}
},
{
"appleNode" : {
"parent" : "399B35A7-3307-4EF6-8B4C-1B83A8F734CD",
"treePart" : {
"apple" : {
"name" : "apple",
"size" : 2
}
},
"uuid" : "0349C0DF-FE58-4D8E-AA72-7466749EB1D6"
}
},
{
"appleNode" : {
"parent" : "6DB14BD5-3E4A-40C4-8EBF-FBD3CC6050C7",
"treePart" : {
"apple" : {
"name" : "apple",
"size" : 2
}
},
"uuid" : "9FCCDBF6-27A7-4E21-8681-5F3E63330504"
}
}
]
""".data(using: .utf8)!
do {
print( "begin decoding" )
/* This currently produces an error: Playground execution aborted: error: Execution was interrupted, reason: signal SIGABRT. The process has been left at the point where it was interrupted, use "thread return -x" to return to the state before expression evaluation.
let decodedTree = try decoder.decode( [AnyTreePartNode].self, from: jsonTree )
print( decodedTree.first( where: { [=12=].wrappedTreePartNode.treePart.wrappedTreePart is Trunk } )! )
*/
} catch let error {
print( error )
}
AnyTreePartNode 中的解码函数应该如何解码 JSON？我错过了什么？
我有变化只是从 unowned var wrappedTreePartNode: TreePartNodeBase 行删除 unowned
并编译了相同的代码。
结果：
打印解码后的中继节点时的预期结果：Trunk { Branch { Apple }, Branch { Branch { Apple } } } 开始解码 [树干，树枝，树枝，树枝，苹果，苹果]
代码：
//
// ViewController.swift
// TestDrive
//
// Created by Mahipal on 25/04/18.
// Copyright © 2018 Vandana. All rights reserved.
//
import UIKit
class ViewController: UIViewController {
override func viewDidLoad() {
super.viewDidLoad()
// Do any additional setup after loading the view, typically from a nib.
////////////// Test (The actual usage of the implementation above)
let trunk = Trunk()
let branch1 = Branch()
let branch2 = Branch()
let branch3 = Branch()
let apple1 = Apple()
let apple2 = Apple()
let trunkNode = TreePartNode<Trunk>( trunk )
let branchNode1 = TreePartNode<Branch>( branch1 )
let branchNode2 = TreePartNode<Branch>( branch2 )
let branchNode3 = TreePartNode<Branch>( branch3 )
let appleNode1 = TreePartNode<Apple>( apple1 )
let appleNode2 = TreePartNode<Apple>( apple2 )
trunkNode.add( child: branchNode1 )
trunkNode.add( child: branchNode2 )
branchNode2.add( child: branchNode3 )
branchNode1.add( child: appleNode1 )
branchNode3.add( child: appleNode2 )
let tree = [trunkNode.equatableSelf,
branchNode1.equatableSelf,
branchNode2.equatableSelf,
branchNode3.equatableSelf,
appleNode1.equatableSelf,
appleNode2.equatableSelf]
print( "expected result when printing the decoded trunk node: \(trunkNode)" )
let encoder = JSONEncoder()
let decoder = JSONDecoder()
encoder.outputFormatting = [.prettyPrinted, .sortedKeys]
// This is how the encoded tree looks like
let jsonTree = """
[
{
"trunkNode" : {
"children" : [
"399B35A7-3307-4EF6-8B4C-1B83A8F734CD",
"60582654-13B9-40D0-8275-3C6649614069"
],
"treePart" : {
"trunk" : {
"color" : "#CCC",
"name" : "trunk"
}
},
"uuid" : "55748AEB-271E-4560-9EE8-F00C670C8896"
}
},
{
"branchNode" : {
"children" : [
"0349C0DF-FE58-4D8E-AA72-7466749EB1D6"
],
"parent" : "55748AEB-271E-4560-9EE8-F00C670C8896",
"treePart" : {
"branch" : {
"length" : 4,
"name" : "branch"
}
},
"uuid" : "399B35A7-3307-4EF6-8B4C-1B83A8F734CD"
}
},
{
"branchNode" : {
"children" : [
"6DB14BD5-3E4A-40C4-8EBF-FBD3CC6050C7"
],
"parent" : "55748AEB-271E-4560-9EE8-F00C670C8896",
"treePart" : {
"branch" : {
"length" : 4,
"name" : "branch"
}
},
"uuid" : "60582654-13B9-40D0-8275-3C6649614069"
}
},
{
"branchNode" : {
"children" : [
"9FCCDBF6-27A7-4E21-8681-5F3E63330504"
],
"parent" : "60582654-13B9-40D0-8275-3C6649614069",
"treePart" : {
"branch" : {
"length" : 4,
"name" : "branch"
}
},
"uuid" : "6DB14BD5-3E4A-40C4-8EBF-FBD3CC6050C7"
}
},
{
"appleNode" : {
"parent" : "399B35A7-3307-4EF6-8B4C-1B83A8F734CD",
"treePart" : {
"apple" : {
"name" : "apple",
"size" : 2
}
},
"uuid" : "0349C0DF-FE58-4D8E-AA72-7466749EB1D6"
}
},
{
"appleNode" : {
"parent" : "6DB14BD5-3E4A-40C4-8EBF-FBD3CC6050C7",
"treePart" : {
"apple" : {
"name" : "apple",
"size" : 2
}
},
"uuid" : "9FCCDBF6-27A7-4E21-8681-5F3E63330504"
}
}
]
""".data(using: .utf8)!
do {
print( "begin decoding" )
// This currently produces an error: Playground execution aborted: error: Execution was interrupted, reason: signal SIGABRT. The process has been left at the point where it was interrupted, use "thread return -x" to return to the state before expression evaluation.
let decodedTree = try decoder.decode( [AnyTreePartNode].self, from: jsonTree )
print( decodedTree )
} catch let error {
print( error )
}
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
// Dispose of any resources that can be recreated.
}
}
import Foundation
///////////// TreePart -> implemented by Trunk, Branch, Apple and AnyTreePart
protocol TreePart: Codable {
var name: String { get set }
func isEqualTo( _ other: TreePart ) -> Bool
func asEquatable() -> AnyTreePart
}
extension TreePart where Self: Equatable {
func isEqualTo( _ other: TreePart ) -> Bool {
guard let otherTreePart = other as? Self else { return false }
return self == otherTreePart
}
func asEquatable() -> AnyTreePart {
return AnyTreePart( self )
}
}
///////////// AnyTreePart -> wrapper for Trunk, Branch and Apple
class AnyTreePart: TreePart, Codable {
var wrappedTreePart: TreePart
var name: String {
get {
return self.wrappedTreePart.name
}
set {
self.wrappedTreePart.name = newValue
}
}
init( _ treePart: TreePart ) {
self.wrappedTreePart = treePart
}
// MARK: Codable
enum CodingKeys: String, CodingKey {
case trunk,
branch,
apple
}
required convenience init( from decoder: Decoder ) throws {
let container = try decoder.container( keyedBy: CodingKeys.self )
var treePart: TreePart?
if let trunk = try container.decodeIfPresent( Trunk.self, forKey: .trunk ) {
treePart = trunk
}
if let branch = try container.decodeIfPresent( Branch.self, forKey: .branch ) {
treePart = branch
}
if let apple = try container.decodeIfPresent( Apple.self, forKey: .apple ) {
treePart = apple
}
guard let foundTreePart = treePart else {
let context = DecodingError.Context( codingPath: [CodingKeys.trunk, CodingKeys.branch, CodingKeys.apple], debugDescription: "Could not find the treePart key" )
throw DecodingError.keyNotFound( CodingKeys.trunk, context )
}
self.init( foundTreePart )
}
func encode( to encoder: Encoder ) throws {
var container = encoder.container( keyedBy: CodingKeys.self )
switch self.wrappedTreePart {
case let trunk as Trunk:
try container.encode( trunk, forKey: .trunk )
case let branch as Branch:
try container.encode( branch, forKey: .branch )
case let apple as Apple:
try container.encode( apple, forKey: .apple )
default:
fatalError( "Encoding error: No encoding implementation for \( type( of: self.wrappedTreePart ) )" )
}
}
}
extension AnyTreePart: Equatable {
static func ==( lhs: AnyTreePart, rhs: AnyTreePart ) -> Bool {
return lhs.wrappedTreePart.isEqualTo( rhs.wrappedTreePart )
}
}
///////////// TreePartNodeBase -> implemented by TreePartNode<T: TreePart> and AnyTreePartNode
protocol TreePartNodeBase: class {
var treePart: AnyTreePart { get set }
var uuid: UUID { get }
var parent: AnyTreePartNode? { get set }
var weakChildren: NSPointerArray { get }
func isEqualTo( _ other: TreePartNodeBase ) -> Bool
func asEquatable() -> AnyTreePartNode
}
extension TreePartNodeBase where Self: Equatable {
func isEqualTo( _ other: TreePartNodeBase ) -> Bool {
guard let otherTreePartNode = other as? Self else { return false }
return self == otherTreePartNode &&
self.treePart == other.treePart &&
self.uuid == other.uuid &&
self.parent == other.parent &&
self.children == other.children
}
func asEquatable() -> AnyTreePartNode {
return AnyTreePartNode( self )
}
}
extension TreePartNodeBase {
var children: [AnyTreePartNode] {
guard let allNodes = self.weakChildren.allObjects as? [AnyTreePartNode] else {
fatalError( "The children nodes are not of type \( type( of: AnyTreePartNode.self ) )" )
}
return allNodes
}
}
///////////// AnyTreePartNode -> wrapper of TreePartNode<T: TreePart>
class AnyTreePartNode: TreePartNodeBase, Codable {
var wrappedTreePartNode: TreePartNodeBase
var treePart: AnyTreePart {
get {
return self.wrappedTreePartNode.treePart
}
set {
self.wrappedTreePartNode.treePart = newValue
}
}
var uuid: UUID {
return self.wrappedTreePartNode.uuid
}
/// The parent node
weak var parent: AnyTreePartNode? {
get {
return self.wrappedTreePartNode.parent
}
set {
self.wrappedTreePartNode.parent = newValue
}
}
/// The weak references to the children of this node
var weakChildren: NSPointerArray {
return self.wrappedTreePartNode.weakChildren
}
init( _ treePartNode: TreePartNodeBase ) {
self.wrappedTreePartNode = treePartNode
}
// MARK: Codable
enum CodingKeys: String, CodingKey {
case trunkNode,
branchNode,
appleNode
}
required convenience init( from decoder: Decoder ) throws {
let container = try decoder.container( keyedBy: CodingKeys.self)
// This attempt of decoding possible nodes doesn't work
if let trunkNode: TreePartNode<Trunk> = try container.decodeIfPresent( TreePartNode<Trunk>.self, forKey: .trunkNode ) {
self.init( trunkNode )
} else if let branchNode: TreePartNode<Branch> = try container
.decodeIfPresent( TreePartNode<Branch>.self, forKey: .branchNode ) {
self.init( branchNode )
} else if let appleNode: TreePartNode<Apple> = try container
.decodeIfPresent( TreePartNode<Apple>.self, forKey: .appleNode ) {
self.init( appleNode )
} else {
let context = DecodingError.Context( codingPath: [CodingKeys.trunkNode,
CodingKeys.branchNode,
CodingKeys.appleNode],
debugDescription: "Could not find the treePart node key" )
throw DecodingError.keyNotFound( CodingKeys.trunkNode, context )
}
// TODO recreating the connections between the nodes should happen after all objects are decoded and will be done based on the UUIDs
}
func encode( to encoder: Encoder ) throws {
var container = encoder.container( keyedBy: CodingKeys.self )
switch self.wrappedTreePartNode {
case let trunkNode as TreePartNode<Trunk>:
try container.encode( trunkNode, forKey: .trunkNode )
case let branchNode as TreePartNode<Branch>:
try container.encode( branchNode, forKey: .branchNode )
case let appleNode as TreePartNode<Apple>:
try container.encode( appleNode, forKey: .appleNode )
default:
fatalError( "Encoding error: No encoding implementation for \( type( of: self.wrappedTreePartNode ) )" )
}
}
}
extension AnyTreePartNode: Equatable {
static func ==( lhs: AnyTreePartNode, rhs: AnyTreePartNode ) -> Bool {
return lhs.wrappedTreePartNode.isEqualTo( rhs.wrappedTreePartNode )
}
}
// enables printing of the wrapped tree part and its child elements
extension AnyTreePartNode: CustomStringConvertible {
var description: String {
var text = "\( type( of: self.wrappedTreePartNode.treePart.wrappedTreePart ))"
if !self.children.isEmpty {
text += " { " + self.children.map { [=10=].description }.joined( separator: ", " ) + " }"
}
return text
}
}
///////////// TreeParts (Trunk, Branch and Apple)
class Trunk: TreePart, Codable, Equatable {
var name: String
var color: String
init( name: String = "trunk",
color: String = "#CCC" ) {
self.name = name
self.color = color
}
static func ==(lhs: Trunk, rhs: Trunk) -> Bool {
return lhs.name == rhs.name &&
lhs.color == rhs.color
}
}
class Branch: TreePart, Codable, Equatable {
var name: String
var length: Int
init( name: String = "branch",
length: Int = 4 ) {
self.name = name
self.length = length
}
static func ==(lhs: Branch, rhs: Branch) -> Bool {
return lhs.name == rhs.name &&
lhs.length == rhs.length
}
}
class Apple: TreePart, Codable, Equatable {
var name: String
var size: Int
init( name: String = "apple",
size: Int = 2 ) {
self.name = name
self.size = size
}
static func ==(lhs: Apple, rhs: Apple) -> Bool {
return lhs.name == rhs.name &&
lhs.size == rhs.size
}
}
///////////// TreePartNode -> The node in the tree that contains the TreePart
class TreePartNode<T: TreePart>: TreePartNodeBase, Codable {
var equatableSelf: AnyTreePartNode!
var uuid: UUID
var treePart: AnyTreePart
var weakChildren = NSPointerArray.weakObjects()
private var parentUuid : UUID?
private var childrenUuids : [UUID]?
weak var parent: AnyTreePartNode? {
willSet {
if newValue == nil {
// unrelated code
// ... removes the references to this object in the parent node, if it exists
}
}
}
init( _ treePart: AnyTreePart,
uuid: UUID = UUID() ) {
self.treePart = treePart
self.uuid = uuid
self.equatableSelf = self.asEquatable()
}
convenience init( _ treePart: T,
uuid: UUID = UUID() ) {
self.init( treePart.asEquatable(),
uuid: uuid )
}
init( _ treePart: AnyTreePart,
uuid: UUID,
parentUuid: UUID?,
childrenUuids: [UUID]?) {
self.treePart = treePart
self.uuid = uuid
self.parentUuid = parentUuid
self.childrenUuids = childrenUuids
self.equatableSelf = self.asEquatable()
}
private func add( child: AnyTreePartNode ) {
child.parent = self.equatableSelf
self.weakChildren.addObject( child )
}
private func set( parent: AnyTreePartNode ) {
self.parent = parent
parent.weakChildren.addObject( self.equatableSelf )
}
// MARK: Codable
enum CodingKeys: String, CodingKey {
case treePart,
uuid,
parent,
children,
parentPort
}
required convenience init( from decoder: Decoder ) throws {
let container = try decoder.container( keyedBy: CodingKeys.self )
// non-optional values
let uuid: UUID = try container.decode( UUID.self, forKey: .uuid )
let treePart: AnyTreePart = try container.decode( AnyTreePart.self, forKey: .treePart )
// optional values
let childrenUuids: [UUID]? = try container.decodeIfPresent( [UUID].self, forKey: .children )
let parentUuid: UUID? = try container.decodeIfPresent( UUID.self, forKey: .parent )
self.init( treePart,
uuid: uuid,
parentUuid: parentUuid,
childrenUuids: childrenUuids)
}
func encode( to encoder: Encoder ) throws {
var container = encoder.container( keyedBy: CodingKeys.self )
// non-optional values
try container.encode( self.treePart, forKey: .treePart )
try container.encode( self.uuid, forKey: .uuid )
// optional values
if !self.children.isEmpty {
try container.encode( self.children.map { [=10=].uuid }, forKey: .children )
}
try container.encodeIfPresent( self.parent?.uuid, forKey: .parent )
}
}
extension TreePartNode: Equatable {
static func ==( lhs: TreePartNode, rhs: TreePartNode ) -> Bool {
return lhs.treePart == rhs.treePart &&
lhs.parent == rhs.parent &&
lhs.children == rhs.children
}
}
// enables printing of the wrapped tree part and its child elements
extension TreePartNode: CustomStringConvertible {
var description: String {
var text = "\( type( of: self.treePart.wrappedTreePart ))"
if !self.children.isEmpty {
text += " { " + self.children.map { [=10=].description }.joined( separator: ", " ) + " }"
}
return text
}
}
// MARK: functions for adding connections to other TreeParts for each specific TreePart type
extension TreePartNode where T: Trunk {
func add( child branch: TreePartNode<Branch> ) {
self.add( child: branch.equatableSelf )
}
}
extension TreePartNode where T: Branch {
func add( child apple: TreePartNode<Apple> ) {
self.add( child: apple.equatableSelf )
}
func add( child branch: TreePartNode<Branch> ) {
self.add( child: branch.equatableSelf )
}
func set( parent branch: TreePartNode<Branch> ) {
self.set( parent: branch.equatableSelf )
}
func set( parent trunk: TreePartNode<Trunk> ) {
self.set( parent: trunk.equatableSelf )
}
}
extension TreePartNode where T: Apple {
func set( parent branch: TreePartNode<Branch> ) {
self.set( parent: branch.equatableSelf )
}
}
////////////// Helper
extension NSPointerArray {
func addObject( _ object: AnyObject? ) {
guard let strongObject = object else { return }
let pointer = Unmanaged.passUnretained( strongObject ).toOpaque()
self.addPointer( pointer )
}
}