【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 18:32:22.886 NeuCopy[3013:303] dog is releaseing

Program ended with exit code: 0