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• 概念
• 内存管理
• NSString的copy实例
• 对象的copy实例

一、概念

目的：在改变原有对象的时候，不会改变新对象的值

1. Copy：实现NSCopying协议，创建的是一个不可变副本
2. MutableCopy：实现NSMutableCopying协议，创建的是一个可变副本

二、内存管理

1. 深拷贝：产生新的对象，所以源对象计数器不变>>>对象拷贝
2. 浅拷贝：不产生新对象，所以源对象计数器加一>>>指针拷贝（因为对象本身不可以变，所有没有必要再创建一个对象）

三、NSString的copy实例

////  main.m//  Copy语法////  Created by apple on 14-3-28.//  Copyright (c) 2014年 apple. All rights reserved.//#import 
     
      void test1(){    NSString *str = [NSString stringWithFormat:@"age is %i", 10];    NSString *str1 = [str copy];        NSLog(@"%i", str == str1);        NSString *str2 = [str mutableCopy];        NSLog(@"%i", str2 == str);}void test2(){    NSMutableString *str = [NSMutableString stringWithFormat:@"age is %i", 11];        NSString *str1 = [str copy];    NSMutableString *str2 = [str mutableCopy];        [str appendFormat:@"1"];        NSLog(@"%i", str == str2);    NSLog(@"%i", str == str1);    NSLog(@"%@", str);    NSLog(@"%@", str1);}int main(int argc, const char * argv[]){    @autoreleasepool {                test2();            }    return 0;}
     

四、对象拷贝的实例

对象的拷贝，主要注意点

1.  必须实现NSCopying协议
2. 需要重写- (id)copyWithZone:(NSZone *)zone方法
3. 代码中 self class的引用

1⃣️GoodStudent.h

////  GoodStudent.h//  Student的Copy用法////  Created by apple on 14-3-28.//  Copyright (c) 2014年 apple. All rights reserved.//#import "Student.h"@interface GoodStudent : Student@property (nonatomic, assign) int age;+(id)goodStudentWithName:(NSString *)name withAge:(int)age;@end

 

2⃣️GoodStudent.m

////  GoodStudent.m//  Student的Copy用法////  Created by apple on 14-3-28.//  Copyright (c) 2014年 apple. All rights reserved.//#import "GoodStudent.h"@implementation GoodStudent+(id)goodStudentWithName:(NSString *)name withAge:(int)age{    GoodStudent *stu = [super studentWithName:name];    stu.age = age;        return stu;}-(id)copyWithZone:(NSZone *)zone{    GoodStudent *copy = [super copyWithZone:zone];    copy.age = self.age;        return copy;}-(NSString *)description{    return [NSString stringWithFormat:@"%@-%i", self.name, self.age];}@end

 

3⃣️Student.h

////  Student.h//  Student的Copy用法////  Created by apple on 14-3-28.//  Copyright (c) 2014年 apple. All rights reserved.//#import 
     
      @interface Student : NSObject 
      
       @property (nonatomic, copy) NSString *name;+(id)studentWithName:(NSString*)name;@end
      
     

 

4⃣️Student.m

////  Student.m//  Student的Copy用法////  Created by apple on 14-3-28.//  Copyright (c) 2014年 apple. All rights reserved.//#import "Student.h"@implementation Student+(id)studentWithName:(NSString *)name{    Student *stu = [[[[self class] alloc] init] autorelease];    stu.name = name;        return stu;}- (id)copyWithZone:(NSZone *)zone{    Student *copy = [[self class] allocWithZone:zone];        copy.name = self.name;        return copy;}-(NSString *)description{    return [NSString stringWithFormat:@"%@", self.name];}-(void)dealloc{    [_name release];    [super dealloc];}@end

 

main.m

////  main.m//  Student的Copy用法////  Created by apple on 14-3-28.//  Copyright (c) 2014年 apple. All rights reserved.//#import 
     
      #import "GoodStudent.h"void test1(){    Student *stu = [Student studentWithName:@"name1"];    Student *stu1 = [stu copy];        NSLog(@"%@", stu);    NSLog(@"%@", stu1);}void test2(){    GoodStudent *stu1 = [GoodStudent goodStudentWithName:@"name1" withAge:10];        GoodStudent *stu2 = [stu1 copy];        NSLog(@"%@", stu1);    NSLog(@"%@", stu2);    }int main(int argc, const char * argv[]){    @autoreleasepool {                test2();            }    return 0;}