浅拷贝与深拷贝

浅拷贝不产生新的对象

深拷贝需要重新创建对象

没啥说的看代码

 1 #import <Foundation/Foundation.h>
 2 #import "Person.h"
 3 int main(int argc, const char * argv[]) {
 4     @autoreleasepool {
 5         // 浅拷贝 不产生新的对象
 6         // 深拷贝 重新创建对象
 7         Person * p = [[Person alloc] init];
 8         p.name = @"Tom";
 9         p.age = 18;
10         Person * p2 = [p copy];
11         NSLog(@"%p %p",p,p2);
12         NSLog(@"%@ %@",p,p2);
13         // 浅拷贝
14         NSString * str1 = @"abc";
15         NSString * str2 = [str1 copy];
16         
17         NSLog(@"%p %p",str1,str2);
18         // 深拷贝
19         NSMutableString * mustr1 = [[NSMutableString alloc] initWithString:@"bcd"];
20         NSMutableString * mustr2 = [mustr1 copy];
21         NSLog(@"%p %p",mustr1,mustr2);
22 //        @property的属性 NSString 类型要用copy
23         // 如果指针指向NSString类型的字符串,copy和retain操作是一样的,只会对引用计数retainCount进行操作 copy 为浅拷贝
24         // 如果指针指向NSMutableString的时候,copy操作不仅会对retainCount进行加减,还会重新创建开辟内存空间,存储指向的对象,而retain操作只会对字符串的引用技术进行加减 copy为深拷贝
25         // NSString block  copy
26     }
27     return 0;
28 }

main.m

1 #import <Foundation/Foundation.h>
2 
3 @interface Person : NSObject<NSCopying>
4 @property (nonatomic,copy) NSString * name;
5 @property (nonatomic,assign) int age;
6 @end

Person.h

 1 #import "Person.h"
 2 
 3 @implementation Person
 4 - (id)copyWithZone:(NSZone *)zone {
 5     // 1 实现对象的直接拷贝 也称为浅拷贝
 6 //    return self;
 7     // 2 深拷贝
 8     // 重新创建一个对象
 9     Person * p = [[Person alloc] init];
10     p.name = self.name;
11     p.age = self.age;
12     return p;
13 }
14 - (NSString *)description {
15     return [NSString stringWithFormat:@"name:%@ age:%d",_name,_age];
16 }
17 @end

Person.m

运行结果

2015-11-15 20:47:08.460 02-浅拷贝和深拷贝[749:49637] 0x1006001e0 0x1006003d0

2015-11-15 20:47:08.462 02-浅拷贝和深拷贝[749:49637] name:Tom age:18 name:Tom age:18

2015-11-15 20:47:08.462 02-浅拷贝和深拷贝[749:49637] 0x1000042e0 0x1000042e0

2015-11-15 20:47:08.462 02-浅拷贝和深拷贝[749:49637] 0x103000160 0x64636235

Program ended with exit code: 0