【Object-C】Copy




-copyWithZone:

Returns a new instance that’s a copy of the receiver. (required)

-mutableCopy

Returns the object returned by mutableCopyWithZone: where the zone is nil.

Declaration:

- (id)copyWithZone:(NSZone *)zone

- (id)mutableCopy

简单的说，copy方法用于复制对象的副本，并返回对象的不可变副本（即使对象本身可变）。

mutablecopy方法则用于复制对象的可变副本，总是返回对象的可变副本（即使被复制对象的本身是不可变的）。

当程序对复制的原对象副本进行修改时，原对象不会受到影响。

//
//  main.m
//  NeuCopy
//
//  Created by mac on 14-12-1.
//  Copyright (c) 2014年 mac. All rights reserved.
//

#import <Foundation/Foundation.h>
#import "People.h"
#import "Dog.h"
#import "GoodPeople.h"

/*
 
copy 意义对于非可变对象来说，并不是产生新的对象，
而对于可变对象来说，是产生一个新的对象
 
multablecopy
 
对于非可变对象的话，也是产生一个可变对象，
对于可变对象来说，自然也是产生一个可变对象
 

*/

int main(int argc, const char * argv[]) {
    @autoreleasepool {
       
        //用alloc方法新建一个p1对象
        People * p1 = [[People alloc]init];
        p1.age = 45;//设置age属性
       
        //使用copy方法复制p2对象
        People * p2 = [p1 copy];
        p2.age = 32;
        //输出p1，p2及其属性
        NSLog(@"实例对象p1:%@,p1的副p2:%@, %i,%i",p1,p2,p1.age,p2.age);
       
        //分别用alloc、copy、retain方法创建对象。
        Dog * dog1 = [[Dog alloc]initWithColor:4];
        Dog * dog2 =  [dog1 copy];
        Dog * dog3 = [dog1 retain];
        //查看对象返回值
        NSLog(@"%@ ,%@ , %@ ,%i, %i",dog1,dog2,dog3,dog1.color,dog2.color);
       
       
     
        Dog * dog = [[Dog alloc]init];
        GoodPeople * gp = [[GoodPeople alloc]init];
       
        gp.dog = dog;
        GoodPeople * gp1 = [gp copy];
        NSLog(@"dog:%@, gp:%@, gp1:%@",dog,gp.dog,gp1.dog);
        gp1.sex = 0;
       
        //释放内存
        [dog release];
        [gp release];
        [gp1 release];
        [p1 release];
        [p2 release];
       
    }
    return 0;

}

#import "People.h"

@implementation People

-(id)copyWithZone:(NSZone *)zone
{
      //深拷贝，为copy副本申请新的内存空间
//    People *p = [[self class] allocWithZone:zone];
//   
//    p.age = self.age;
//   
//    return p;
    //浅拷贝，将copy副本的self指针指向原对象的内存地址，原对象和副本地址将会是同一个
    return  [self retain];
}
@end

===>

2014-12-01 18:32:22.882 NeuCopy[3013:303] 实例对象p1:<People: 0x100102300>,p1的副p2:<People: 0x100102300>, 32,32
2014-12-01 18:32:22.884 NeuCopy[3013:303] <Dog: 0x1006013b0> ,<Dog: 0x100602290> , <Dog: 0x1006013b0> ,4, 4
2014-12-01 18:32:22.885 NeuCopy[3013:303] dog:<Dog: 0x10010a050>, gp:<Dog: 0x10010bac0>, gp1:<Dog: 0x10010bac0>
2014-12-01 18:32:22.886 NeuCopy[3013:303] dog is releaseing
2014-12-01 18:32:22.886 NeuCopy[3013:303] dog is releaseing

Program ended with exit code: 0