如何在Swift 3中使用NSCoder對[Character：Int]屬性進行編碼？

Question

import UIKit 

class Foo: NSObject, NSCoding { 
    var cx: [Character : Int] 

    init(cx: [Character : Int]) { 
     self.cx = cx 
    } 

    // MARK: - <NSCoding> 

    required convenience init(coder aDecoder: NSCoder) { 
     let cx = aDecoder.decodeObject(forKey: "cxKey") as! [Character : Int] 
     self.init(cx: cx) 
    } 

    func encode(with aCoder: NSCoder) { 
     aCoder.encode(cx, forKey: "cxKey") 
    } 
} 

電話：

class ViewController: UIViewController { 

    override func viewDidLoad() { 
     super.viewDidLoad() 
     // Do any additional setup after loading the view, typically from a nib. 

     var foo = Foo(cx: ["C": 5, "X": 6]) 

     let encodedData = NSKeyedArchiver.archivedData(withRootObject: foo) 
     print("encodedData: \(encodedData))") 

     if let foo1 = NSKeyedUnarchiver.unarchiveObject(with: encodedData) as? Foo { 
      print("cx = ", foo1.cx) 
     } else{ 
      print("There is an issue") 
     } 
    } 
} 

Xcode中拋出一個錯誤：***終止應用程序由於未捕獲的異常 'NSInvalidArgumentException'，原因是：「 - [_ SwiftValue encodeWithCoder：]：無法識別的選擇發送到實例

Answer 1

原因

這是因爲在cx的Character -typed鍵將被作爲盒裝對象_SwiftValue其中將被髮送encodeWithCoder:，這導致無法識別的選擇器異常。

看到的SwiftValue.h頂部的評論：

This implements the Objective-C class that is used to carry Swift values that have been bridged to Objective-C objects without special handling. The class is opaque to user code, but is NSObject - and NSCopying - conforming and is understood by the Swift runtime for dynamic casting back to the contained type.

解決方案

如果你可以改變的cx類型[String : Int]，一切都會開箱即用（沒有雙關語意） 。

否則你必須在Foo.encode(with:)中將cx轉換爲可編碼的東西（例如[String : Int]），反之亦然。

有關某些代碼，請參閱How do I encode Character using NSCoder in swift?和How do I encode enum using NSCoder in swift?。