Swift 上的常见可等式 class

Question

我需要 Any Equatable 项目的容器 NOT Generic class（对于示例 UI classes initial from storyboard）。我需要这样

var items: [Equatable]?

但它不起作用，Equatable 需要 Generic。不存在的问题 common Equatable class.

好的 - 转到通用！但是如果我这样做

class Item<Value: Equatable>: Equatable {
   var value: Value
   init(_ value: Value) {
       self.value = value
   }
   //Equatable
   public static func ==(lhs: Item, rhs: Item) -> Bool {
       return (lhs.value == rhs.value)
   }
}

然后我将被迫在我的nonGeneric-UI class中指定类型。像这样

var items: [Item<WhatShouldBeHere?>]?

但我们又遇到了不存在共同点的问题 Equatable class

All Equatable 容器的任何解决方案？

Answer 1

代替存在类型，您需要使用类型橡皮擦：

public struct AnyEquatable: Equatable {
    public let value: Any
    private let equals: (Any) -> Bool

    public init<E: Equatable>(_ value: E) {
        self.value = value
        self.equals = { ([=10=] as? E) == value }
    }

    public static func == (lhs: AnyEquatable, rhs: AnyEquatable) -> Bool {
        return lhs.equals(rhs.value) || rhs.equals(lhs.value)
    }
}

用法示例：

let items = [
    AnyEquatable(1),
    AnyEquatable(1.23),
    AnyEquatable(true),
    AnyEquatable("some string")
]

let desired = "some string"
let desiredAsAnyEquatable = AnyEquatable(desired)
let desiredDescription = String(reflecting: desired)

for item in items {
    let itemDescription = String(reflecting: item.value)
    let isEqualToDesired = item == desiredAsAnyEquatable
    print("\(itemDescription) is \(isEqualToDesired ? "": "not ")equal to \(desiredDescription)")
}

示例输出：

1 is not equal to "some string"

1.23 is not equal to "some string"

true is not equal to "some string"

"some string" is equal to "some string"

Swift 上的常见可等式 class

Common Equatable class on Swift

generics

swift

equatable