我想在
Swift 2中实现一个简单的GKGameModel.苹果的例子在Objective-C中表达,并包含这个方法声明(根据GKGameModel继承的NSCopying协议的要求)：
- (id)copyWithZone:(NSZone *)zone {
AAPLBoard *copy = [[[self class] allocWithZone:zone] init];
[copy setGameModel:self];
return copy;
}
这怎么翻译成Swift 2？在效率和忽视区方面是否适合？
func copyWithZone(zone: NSZone) -> AnyObject {
let copy = GameModel()
// ... copy properties
return copy
}
NSZone已经不再在Objective-C中使用了很长时间.而传递的区域参数被忽略.从allocWithZone引用… docs：
This method exists for historical reasons; memory zones are no longer
used by Objective-C.
你也可以忽略它.
下面是一个如何符合NSCopying协议的例子.
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
附：此示例适用于Xcode Version 7.0 beta 5(7A176x).特别是dynamicType.init(self).
为Swift 3编辑
以下是Swift 3的copyWithZone方法实现,因为dynamicType已被弃用：
func copy(with zone: NSZone? = nil) -> Any
{
return type(of:self).init(self)
}
