如何在Swift 2中符合NSCopying并实现copyWithZone? [英] How to conform to NSCopying and implement copyWithZone in Swift 2?

问题描述

我想在Swift 2中实现一个简单的GKGameModel.Apple的示例在Objective-C中表达，并包含以下方法声明(GKGameModel所继承的协议NSCopying所要求的):

I would like to implement a simple GKGameModel in Swift 2. Apple's example is expressed in Objective-C and includes this method declaration (as required by protocol NSCopyingfrom which GKGameModel inherits):

- (id)copyWithZone:(NSZone *)zone {
    AAPLBoard *copy = [[[self class] allocWithZone:zone] init];
    [copy setGameModel:self];
    return copy;
}

这如何转换为Swift 2?就效率和忽略区域而言，以下内容是否合适?

How does this translate into Swift 2? Is the following appropriate in terms of efficiency and ignoring zone?

func copyWithZone(zone: NSZone) -> AnyObject {
    let copy = GameModel()
    // ... copy properties
    return copy
}

推荐答案

NSZone长时间不在Objective-C中使用.并忽略传递的zone参数.引用allocWithZone...文档:

NSZone is no longer used in Objective-C for a long time. And passed zone argument is ignored. Quote from the allocWithZone... docs:

此方法存在是出于历史原因；内存区域不再 由Objective-C使用.

This method exists for historical reasons; memory zones are no longer used by Objective-C.

您也可以忽略它.

这是一个如何符合NSCopying协议的示例.

Here's an example how to conform to NSCopying protocol.

class GameModel: NSObject, NSCopying {

  var someProperty: Int = 0

  required override init() {
    // This initializer must be required, because another
    // initializer `init(_ model: GameModel)` is required
    // too and we would like to instantiate `GameModel`
    // with simple `GameModel()` as well.
  }

  required init(_ model: GameModel) {
    // This initializer must be required unless `GameModel`
    // class is `final`
    someProperty = model.someProperty
  }

  func copyWithZone(zone: NSZone) -> AnyObject {
    // This is the reason why `init(_ model: GameModel)`
    // must be required, because `GameModel` is not `final`.
    return self.dynamicType.init(self)
  }

}

let model = GameModel()
model.someProperty = 10

let modelCopy = GameModel(model)
modelCopy.someProperty = 20

let anotherModelCopy = modelCopy.copy() as! GameModel
anotherModelCopy.someProperty = 30

print(model.someProperty)             // 10
print(modelCopy.someProperty)         // 20
print(anotherModelCopy.someProperty)  // 30

P.S.本示例适用于Xcode 7.0 beta 5(7A176x).尤其是dynamicType.init(self).

P.S. This example is for Xcode Version 7.0 beta 5 (7A176x). Especially the dynamicType.init(self).

为Swift 3编辑

以下是由于不推荐使用dynamicType的Swift 3的copyWithZone方法实现:

Below is the copyWithZone method implementation for Swift 3 as dynamicType has been deprecated:

func copy(with zone: NSZone? = nil) -> Any
{
    return type(of:self).init(self)
}

这篇关于如何在Swift 2中符合NSCopying并实现copyWithZone?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！