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

#import <Foundation/Foundation.h>
#import "Person.h"
int main(int argc, const char * argv[]) {
    @autoreleasepool {
        // 浅拷贝 不产生新的对象
        // 深拷贝 重新创建对象
        Person * p = [[Person alloc] init];
        p.name = @"Tom";
        p.age = 18;
        Person * p2 = [p copy];
        NSLog(@"%p %p",p,p2);
        NSLog(@"%@ %@",p,p2);
        // 浅拷贝
        NSString * str1 = @"abc";
        NSString * str2 = [str1 copy];
        
        NSLog(@"%p %p",str1,str2);
        // 深拷贝
        NSMutableString * mustr1 = [[NSMutableString alloc] initWithString:@"bcd"];
        NSMutableString * mustr2 = [mustr1 copy];
        NSLog(@"%p %p",mustr1,mustr2);
//        @property的属性 NSString 类型要用copy
        // 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
        // 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
        // NSString block  copy
    }
    return 0;
}

#import <Foundation/Foundation.h>

@interface Person : NSObject<NSCopying>
@property (nonatomic,copy) NSString * name;
@property (nonatomic,assign) int age;
@end

#import "Person.h"

@implementation Person
- (id)copyWithZone:(NSZone *)zone {
    // 1 实现对象的直接拷贝 也称为浅拷贝
//    return self;
    // 2 深拷贝
    // 重新创建一个对象
    Person * p = [[Person alloc] init];
    p.name = self.name;
    p.age = self.age;
    return p;
}
- (NSString *)description {
    return [NSString stringWithFormat:@"name:%@ age:%d",_name,_age];
}
@end

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