【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

簡單的說，copy方法用於複製對象的副本，並返回對象的不可變副本（即使對象本身可變）。

mutablecopy方法則用於複製對象的可變副本，總是返回對象的可變副本（即使被複制對象的本身是不可變的）。

當程序對複製的原對象副本進行修改時，原對象不會受到影響。

//
//  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 意義對於非可變對象來說，並不是產生新的對象，
而對於可變對象來說，是產生一個新的對象
 
multablecopy
 
對於非可變對象的話，也是產生一個可變對象，
對於可變對象來說，自然也是產生一個可變對象
 

*/

int main(int argc, const char * argv[]) {
    @autoreleasepool {
       
        //用alloc方法新建一個p1對象
        People * p1 = [[People alloc]init];
        p1.age = 45;//設置age屬性
       
        //使用copy方法複製p2對象
        People * p2 = [p1 copy];
        p2.age = 32;
        //輸出p1，p2及其屬性
        NSLog(@"實例對象p1:%@,p1的副p2:%@, %i,%i",p1,p2,p1.age,p2.age);
       
        //分別用alloc、copy、retain方法創建對象。
        Dog * dog1 = [[Dog alloc]initWithColor:4];
        Dog * dog2 =  [dog1 copy];
        Dog * dog3 = [dog1 retain];
        //查看對象返回值
        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;
       
        //釋放內存
        [dog release];
        [gp release];
        [gp1 release];
        [p1 release];
        [p2 release];
       
    }
    return 0;

}

#import "People.h"

@implementation People

-(id)copyWithZone:(NSZone *)zone
{
      //深拷貝，爲copy副本申請新的內存空間
//    People *p = [[self class] allocWithZone:zone];
//   
//    p.age = self.age;
//   
//    return p;
    //淺拷貝，將copy副本的self指針指向原對象的內存地址，原對象和副本地址將會是同一個
    return  [self retain];
}
@end

===>

2014-12-01 18:32:22.882 NeuCopy[3013:303] 實例對象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