iOS开发之深复制浅复制

iOS开发中，对象拥有复制特性，必须实现NSCopying，NSMutableCopying协议，实现该协议的copyWithZone方法和mutableCopyWithZone方法

深拷贝和浅拷贝的区别就在于copyWithZone方法的实现,

浅拷贝代码如下：

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#import <foundation foundation.h="">   @interface Person : NSObject<nscopying> @property(nonatomic,retain)NSString *name; @property(nonatomic,retain)NSString *age;   @end </nscopying></foundation>

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#import "Person.h"   @implementation Person   - (id)copyWithZone:(NSZone *)zone {    //实现自定义浅拷贝     Person *person=[[self class] allocWithZone:zone];     person.age=_age;     person.name=_name;     return person; } @end

main函数为：

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@autoreleasepool {           Person *person=[[Person alloc] init];     person.name=@"andy";     person.age=@"20";           Person *person2=[person copy];     NSLog(@"person 地址为%p,person2地址为%p",person.name,person2.name); }

输出结果为：

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1	2013-09-30 17:48:41.007 FDAS[732:303] person 地址为0x1000022c8,person2地址为0x1000022c8

深拷贝代码如下：

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- (id)copyWithZone:(NSZone *)zone {    //实现自定义浅拷贝     Person *person=[[self class] allocWithZone:zone];     person.age=[_age copy];     person.name=[_age copy];     return person; }

结果：

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1	2013-09-30 17:55:13.603 FDAS[742:303] person 地址为0x1000022c8,person2地址为0x1000022e8

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NSArray *arr=[NSArray arrayWithObjects:@"one",@"two",nil]; NSArray *arr2=[arr copy]; NSLog(@"the dress of arr is %p the dress of arr2 is %p",arr,arr2); NSLog(@"the retainCount is %ld",arr.retainCount);

执行结果为：

2015-09-30 18:01:01.394 FDAS[787:303] the dress of arr is 0x100108320 the dress of arr2 is 0x100108320

2015-09-30 18:01:01.396 FDAS[787:303] the retainCount is 2

结果是一样的，是因为Foundation对于不可变复制对象而言，copy方法做了优化，相当于retain，故retaincount变成2.

相当于 在copyWithZone方法中：return [self retain];

欢迎大家批评指正~