Copy方法
//// main.m// MutableCopy//// Created by rayln on 13-9-13.// Copyright (c) 2013年 rayln. All rights reserved.//#import <Foundation/Foundation.h>#import "Student.h"void copy(){ //若要copy自定义的对象，必须实现NSCopying协议, 并且实现copyWithZone方法 Student *stu = [[Student alloc] init]; Student *stu1 = [stu copy]; [stu release]; [stu1 release];}int main(int argc, const char * argv[]){ @autoreleasepool {#pragma mark - mutablecopy深拷贝 NSString *str1 = @"100"; NSMutableString *str2 = [str1 mutableCopy]; //copy出来的对象需要释放内存 [str2 release]; #pragma mark - copy 浅拷贝 NSString *string1 = @"101"; NSString *string2 = [string1 copy]; //string1对象和string2对象是同一个对象，因为NSString本来就是不可变的 [string2 release]; Student *stu = [[Student alloc] init]; NSMutableString *name = [[NSMutableString alloc] initWithString:@"rayln"]; NSMutableString *passport = [[NSMutableString alloc] initWithString:@"445281"]; stu.name = name; stu.passport = passport; [name appendString:@"Guan"]; [passport appendString:@"1983"]; //由此可见，retain策略的话，外面重新符值，student的name也会改变 //使用copy策略的话，外面重新符值，student的passport还是没有改变 NSLog(@"Student.name:%@ name:%@", stu.name, name); NSLog(@"Student.passport:%@ passport:%@", stu.passport, passport); [name release]; [passport release]; [stu release]; } return 0;}
Student.h
//// Student.h// MutableCopy//// Created by rayln on 13-9-13.// Copyright (c) 2013年 rayln. All rights reserved.//#import <Foundation/Foundation.h>@interface Student : NSObject <NSCopying>//建议NSString对象用copy，其他对象用retain策略@property (nonatomic, retain) NSString *name;@property (nonatomic, copy) NSString *passport;@end
//// Student.m// MutableCopy//// Created by rayln on 13-9-13.// Copyright (c) 2013年 rayln. All rights reserved.//#import "Student.h"@implementation Student//实现copyWithZone方法，使用copy方法必须实现他- (id)copyWithZone:(NSZone *)zone{ Student *stu = [[Student allocWithZone:zone] init]; stu.name = self.name; stu.passport = self.passport; return stu;}- (void)dealloc{ [_name release]; [_passport release]; [super dealloc];}@end