swift 包含两个子项的大纲视图 children

Question

我在 macOS 上使用 swift 4，我有一个 NSOutlineView:

我从核心数据中获取数据。

结构：

实体人（与实体书的关系）
实体书

我对此结果的代码：

@IBOutlet weak var myOutlineView: NSOutlineView!

    let context = (NSApplication.shared.delegate as! AppDelegate).persistentContainer.viewContext
    var people = [Person]()

    override func viewWillAppear() {
       requestPeople()
    }

    func outlineView(_ outlineView: NSOutlineView, viewFor tableColumn: NSTableColumn?, item: Any) -> NSView? {
        let view = outlineView.makeView(withIdentifier: NSUserInterfaceItemIdentifier(rawValue: "Cell"), owner: self) as? CustomCell
        if let person = item as? Person {
           // Show Person
        } else if let book = item as? Book {
            // Show Books
        }
        return view
    }


    func outlineView(_ outlineView: NSOutlineView, numberOfChildrenOfItem item: Any?) -> Int {
        if let person = item as? Person {
            return person.books.count
        }
        return people.count
    }


    func outlineView(_ outlineView: NSOutlineView, child index: Int, ofItem item: Any?) -> Any {
        if let person = item as? Person {
            return person.books[index]
        }
        return people[index]
    }


    func outlineView(_ outlineView: NSOutlineView, isItemExpandable item: Any) -> Bool {
        if let person = item as? Person {
            return person.books.count > 0
        }
        return false
    }



    func requestPeople() {
        let request = NSFetchRequest<Person>(entityName: "Person")
        do {
            people = try context.fetch(request)
            myOutlineView.reloadData()
        } catch { print(error) }
    }

现在我的问题是：我想创建另一个大纲视图。

我的 Book 实体看起来像这样（属性）：

名字
创建日期

我的新大纲视图应该采用这种结构：

+ Year
++ Month
+++ Bookname

但我不知道如何实现这个结构。和我的第一个大纲视图不一样。

有人可以帮我吗？

=======

我想我已经为年份和月份创建了没有重复的数组。为此，我尝试使用此函数来获取数据：

 var year = [String]()
 var month = [String]()
 var books = [Book]()

    func requestBooks() {
        let request = NSFetchRequest<Book>(entityName: "Book")
        do {
            books = try context.fetch(request)

            for x in 0 ...< books.count {

                if !year.contains("\(Calendar.current.component(.year, from: books[x].creationDate))") {
                    year.append("\(Calendar.current.component(.year, from: books[x].creationDate))")
                }

                if !month.contains("\(Calendar.current.component(.month, from: books[x].creationDate))") {
                    month.append("\(Calendar.current.component(.month, from: books[x].creationDate))")
                }

            }

            myOutlineView.reloadData()
        } catch { print(error) }
    }

Answer 1

当您的底层数据结构是分层的（即树结构）时，多级大纲更易于管理。

以下是如何为图书创建 "Tree" 节点 class 的示例：

class BookNode
{
   // levels and relationships, from parent to children
   enum Level { case Top, Year, Month, Book }       
   let subLevels:[Level:Level] = [ .Top:.Year, .Year:.Month, .Month:.Book ]       

   var label    = ""               // description and unique "key"
   var level    = Level.Top        
   var children : [BookNode] = []       
   var book     : Book! = nil      // .Book level will store the actual Book

   // add book to hierarchy, auto-create intermediate levels        
   func add(_ book:Book) 
   {
      var subLabel = ""
      switch level
      {
         case .Top   : subLabel   = String(Calendar.current.component(.year, from:book.creationDate))
         case .Year  : subLabel   = String(Calendar.current.component(.month, from:book.creationDate))
         case .Month : subLabel   = book.name
         case .Book  : self.book  = book  // last level stores the book 
                       return             // and has no children
      }                     
      // Add branch (.Year, .Month) or leaf (.Book) node as needed
      var subNode:BookNode! = children.first{[=10=].label == subLabel}
      if subNode == nil 
      { 
        subNode       = BookNode() 
        subNode.level = subLevels[level]!
        subNode.label = subLabel
        children.append(subNode)
      }
      // keep adding recursively down to .Book level          
      subNode.add(book) 
   }
}

您的数据将存储在 BookNodes 的层次结构中，您可以从提取请求中加载它（您可以像我一样对其进行预排序，或者将其留给 BookNode class）

var topNode = BookNode()

func requestBooks() 
{
  let request = NSFetchRequest<Book>(entityName: "Book")
  do {
       let books = try context.fetch(request)

       topNode = BookNode()
       for book in books.sorted(by:{[=11=].creationDate < .creationDate}) 
       {
          topNode.add(book)
       }
     }
}

有了这个，使用 BookNodes 作为大纲项目将很容易响应你的大纲协议：

func outlineView(_ outlineView: NSOutlineView, viewFor tableColumn: NSTableColumn?, item: Any) -> NSView? 
{
  let view = outlineView.makeView(withIdentifier: NSUserInterfaceItemIdentifier(rawValue: "Cell"), owner: self) as? CustomCell

  let node = (item as? BookNode) ?? topNode
  switch node.level
  { 
     case .Year    : // show year      : node.label
     case .Month   : // show month     : node.label
     case .Book    : // show book name : node.label and/or node.book
     default       : break
  }

  return view
}

func outlineView(_ outlineView: NSOutlineView, numberOfChildrenOfItem item: Any?) -> Int 
{        
  let node = (item as? BookNode) ?? topNode
  return node.children.count        
}


func outlineView(_ outlineView: NSOutlineView, child index: Int, ofItem item: Any?) -> Any 
{
  let node = (item as? BookNode) ?? topNode
  return node.children[index]        
}


func outlineView(_ outlineView: NSOutlineView, isItemExpandable item: Any) -> Bool 
{
  let node = (item as? BookNode) ?? topNode
  return node.children.count > 0        
}

如果您的程序需要允许 adding/changing/removing 本书，BookNode class 可用于反映个人更改（例如，删除一个书子或添加一个新书）。然后，您只需要在大纲上调用 reloadData()，而不必从数据库中取回所有内容。

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