iOS SDK具体解释之NSCopying协议

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http://blog.csdn.net/column/details/huangwenchen-ios-sdk.html

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前言：NSCopy协议是对对象进行拷贝的协议。Copy后的对象和原对象是两个对象，要分开考虑其生命周期。Copy后的对象应当对原始对象不依赖，不影响。
使用NSCopy协议仅仅须要实现一个方法copyWithZone:就可以

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举例

OC

@interface MyModel:NSObject<NSCopying>
@property (copy,nonatomic)NSString * name;
@property (nonatomic)int age;
@end

@implementation MyModel

-(instancetype)copyWithZone:(NSZone *)zone{
    MyModel * copyedModel = [[self.class allocWithZone:zone] init];
    copyedModel->_name = self.name;
    copyedModel->_age = self.age;
    return copyedModel;
}

@end

使用

    MyModel * model = [[MyModel alloc] init];
    model.name = @"wenchen";
    model.age = 24;
    MyModel * copyedModel = [model copy];

然后在LLDB中能够查看对象地址，能够看到是两个独立的对象

(lldb) po copyedModel
<MyModel: 0x7f958971b690>

(lldb) po model
<MyModel: 0x7f958971b5b0>

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Swift

class MyModel:NSObject,NSCopying{
    func copyWithZone(zone: NSZone) -> AnyObject {
        let copyedModel = self.dynamicType()
        return copyedModel
    }
    required override init() {
    }

简单測试

 let model1 = MyModel()
 let model2 = model1.copy()

(lldb) po model1
<SWTest.MyModel: 0x7fafe0476f40>

(lldb) po model2
<SWTest.MyModel: 0x7fafe0476ec0>

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这里顺便提一下，怎样在Swift中声明一个OC中的copy 属性

 @NSCopying var name:NSString?

使用关键字 @NSCopying