iOS中copy的用法

1 深复制：内容拷贝,源对象和副本对象指的是两个不同的对象,源对象引用计数器不变,副本对象引用计数器为1

2 浅复制：指针拷贝,源对象和副本对象指的都是同一个对象,对象引用计数器+1,相当于retain

3 只有不可变对象创建不可变副本(copy)才是浅复制，其它的都是深复制

//
//  main.m
//  CopyTest
//
//  Created by Unisk on 13-9-20.
//  Copyright (c) 2013年 Test. All rights reserved.
//

#import <Foundation/Foundation.h>
#import "Student.h"
#import "GoodStudent.h"


#pragma mark copy
void student()
{
    Student *stu1=[Student studentWithName:@"stu1"];
    Student *stu2=[stu1 copy];
    stu2.name=@"XZQ";
    NSLog(@"%@",stu1);
    NSLog(@"%@",stu2);
    [stu2 release];
}

#pragma mark copy
void goodStudent(){
    GoodStudent *gtu1=[GoodStudent goodStudent:11 name:@"xzq"];
    GoodStudent *gtu2=[gtu1 copy];
    gtu2.age=111;
    gtu2.name=@"google";
    
    NSLog(@"%@",gtu1);
    NSLog(@"%@",gtu2);

    
}



int main(int argc, const char * argv[])
{

    @autoreleasepool {
        goodStudent();
    }
    return 0;
}

#import <Foundation/Foundation.h>

@interface Student : NSObject<NSCopying>

@property (nonatomic,copy) NSString *name;

+(id)studentWithName:(NSString *)name;

@end

//
//  Student.m
//  CopyTest
//
//  Created by Unisk on 13-9-20.
//  Copyright (c) 2013年 Test. All rights reserved.
//

#import "Student.h"

@implementation Student

+(id)studentWithName:(NSString *)name
{
    Student *stu=[[[[self class] alloc] init] autorelease];
    stu.name=name;
    return stu;
}

#pragma mark 对象的拷贝
-(id)copyWithZone:(NSZone *)zone
{
    Student *stu=[[[self class] allocWithZone:zone] init];
    stu.name=self.name;
    return stu;
}


-(NSString *)description
{
    return [NSString stringWithFormat:@"name is %@",_name];
}

- (void)dealloc
{
    [_name release];
    [super dealloc];
}

@end

#import "Student.h"

@interface GoodStudent : Student

@property (nonatomic,assign) int age;

+(id)goodStudent:(int) age name:(NSString *)name;

@end

#import "GoodStudent.h"

@implementation GoodStudent

+(id)goodStudent:(int)age name:(NSString *)name
{
    GoodStudent *goodStu=[GoodStudent studentWithName:name];
    goodStu.age=age;
    return goodStu;
}

-(id)copyWithZone:(NSZone *)zone
{
    GoodStudent *gtu=[super copyWithZone:zone];
    gtu.age=_age;
    return gtu;
}

-(NSString *)description
{
    return [NSString stringWithFormat:@"name=%@,age=%i",self.name,_age];
}

@end