Copy方法

最新推荐文章于 2022-08-12 17:50:03 发布

原创最新推荐文章于 2022-08-12 17:50:03 发布 · 212 阅读

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//
//  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

//
//  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