retain、copy、和mutableCopy 通过实例深入了解它们之间的区别

//    NSString *string = @"origion";//此时所有的retaincount都为-1，retain和release操作都没有效用

//    NSString *string = [NSString stringWithFormat:@"%@",@"origion"];//静态方法。创建对象，内存由系统负责回收

    NSString *string = [[NSString alloc]initWithFormat:@"%@",@"origion"];//alloc创建的对象，内存由用户手动回收

    NSLog(@"stringP = %p,stringContentP=%p,retainCount = %d",&string,string,[string retainCount]);

/*

2015-04-09 15:06:04.914 BlockDemo[5621:60b] stringP = 0xbfffc930,stringContentP=0x8e6e920,retainCount = 1

*/

//操作一：retain

    NSString *retainString = [string retain];//拷贝了指针，没有拷贝内容，两个对象指针 指向同一块内存，retaincount 都为2

    NSLog(@"1retain--stringP = %p,stringContentP=%p,retainCount = %d",&string,string,[string retainCount]);

    NSLog(@"1retain--retainStringP = %p,retainStringContentP=%p,retainCount = %d",&retainString,retainString,[retainString retainCount]);

/*

2015-04-09 15:06:04.915 BlockDemo[5621:60b] 1retain--stringP = 0xbfffc930,stringContentP=0x8e6e920,retainCount = 2

     2015-04-09 15:06:04.916 BlockDemo[5621:60b] 1retain--retainStringP = 0xbfffc92c,retainStringContentP=0x8e6e920,retainCount = 2

*/

 //操作二：retain

    NSString *retainString2 = [retainString retain];//拷贝了指针，没有拷贝内容，两个对象指针 指向同一块内存，retaincount 都为2

    NSLog(@"2retain--stringP = %p,stringContentP=%p,retainCount = %d",&string,string,[string retainCount]);

    NSLog(@"2retain--retainStringP = %p,retainStringContentP=%p,retainCount = %d",&retainString,retainString,[retainString retainCount]);

    NSLog(@"2retain--retainString2P = %p,retainString2ContentP=%p,retainCount = %d",&retainString2,retainString2,[retainString2 retainCount]);

    

/*

2015-04-09 15:06:04.916 BlockDemo[5621:60b] 2retain--stringP = 0xbfffc930,stringContentP=0x8e6e920,retainCount = 3

     2015-04-09 15:06:04.917 BlockDemo[5621:60b] 2retain--retainStringP = 0xbfffc92c,retainStringContentP=0x8e6e920,retainCount = 3

     2015-04-09 15:06:04.917 BlockDemo[5621:60b] 2retain--retainString2P = 0xbfffc928,retainString2ContentP=0x8e6e920,retainCount = 3

*/  

     //操作三：release

    [retainString2 release];//retain后的对象，中得任何一个对象release都会使得retaincount减一

    

    NSLog(@"3release--stringP = %p,stringContentP=%p,retainCount = %d",&string,string,[string retainCount]);

    NSLog(@"3release--retainStringP = %p,retainStringContentP=%p,retainCount = %d",&retainString,retainString,[retainString retainCount]);

    NSLog(@"3release--retainString2P = %p,retainString2ContentP=%p,retainCount = %d",&retainString2,retainString2,[retainString2 retainCount]);

/*

2015-04-09 15:06:04.918 BlockDemo[5621:60b] 3release--stringP = 0xbfffc930,stringContentP=0x8e6e920,retainCount = 2

     2015-04-09 15:06:04.918 BlockDemo[5621:60b] 3release--retainStringP = 0xbfffc92c,retainStringContentP=0x8e6e920,retainCount = 2

     2015-04-09 15:06:04.918 BlockDemo[5621:60b] 3release--retainString2P = 0xbfffc928,retainString2ContentP=0x8e6e920,retainCount = 2

*/

//操作四：copy

    NSString *retainString3 = [retainString copy];//浅拷贝或者是弱引用，这里只拷贝指针，拷贝后指针和之前的指向的是同一块内存，自然输出的内容也一致

    NSLog(@"4copy--stringP = %p,stringContentP=%p,retainCount = %d",&string,string,[string retainCount]);

    NSLog(@"4copy--retainStringP = %p,retainStringContentP=%p,retainCount = %d",&retainString,retainString,[retainString retainCount]);

    NSLog(@"4copy--retainString2P = %p,retainString2ContentP=%p,retainCount = %d",&retainString2,retainString2,[retainString2 retainCount]);

    NSLog(@"4copy--retainString3P = %p,retainString3ContentP=%p,retainCount = %d",&retainString3,retainString3,[retainString3 retainCount]);

  /*

2015-04-09 15:06:04.919 BlockDemo[5621:60b] 4copy--stringP = 0xbfffc930,stringContentP=0x8e6e920,retainCount = 3

     2015-04-09 15:06:04.919 BlockDemo[5621:60b] 4copy--retainStringP = 0xbfffc92c,retainStringContentP=0x8e6e920,retainCount = 3

     2015-04-09 15:06:04.920 BlockDemo[5621:60b] 4copy--retainString2P = 0xbfffc928,retainString2ContentP=0x8e6e920,retainCount = 3

     2015-04-09 15:06:04.921 BlockDemo[5621:60b] 4copy--retainString3P = 0xbfffc924,retainString3ContentP=0x8e6e920,retainCount = 3

 

*/

//操作四：release

    [retainString3 release];//因为retain后的对象和原来的对象的内容是同一块内存，所以任何一个对象release一次，都会导致这块内存的引用次数减一

    NSLog(@"5release--stringP = %p,stringContentP=%p,retainCount = %d",&string,string,[string retainCount]);

    NSLog(@"5release--retainStringP = %p,retainStringContentP=%p,retainCount = %d",&retainString,retainString,[retainString retainCount]);

    NSLog(@"5release--retainString2P = %p,retainString2ContentP=%p,retainCount = %d",&retainString2,retainString2,[retainString2 retainCount]);

    NSLog(@"5release--retainString3P = %p,retainString3ContentP=%p,retainCount = %d",&retainString3,retainString3,[retainString3 retainCount]);

/*

2015-04-09 15:06:04.921 BlockDemo[5621:60b] 5release--stringP = 0xbfffc930,stringContentP=0x8e6e920,retainCount = 2

     2015-04-09 15:06:04.922 BlockDemo[5621:60b] 5release--retainStringP = 0xbfffc92c,retainStringContentP=0x8e6e920,retainCount = 2

     2015-04-09 15:06:04.922 BlockDemo[5621:60b] 5release--retainString2P = 0xbfffc928,retainString2ContentP=0x8e6e920,retainCount = 2

     2015-04-09 15:06:04.923 BlockDemo[5621:60b] 5release--retainString3P = 0xbfffc924,retainString3ContentP=0x8e6e920,retainCount = 2

*/

    

//操作五：mutableCopy    

NSString *retainString4 = [retainString mutableCopy];‍‍//深copy会产生新的对象，指针和存放内容的地址都拷贝了一份儿新的，原来的对象的retaincount不变，新对象的retaincount为1‍‍

    NSLog(@"6mutableCopy--stringP = %p,stringContentP=%p,retainCount = %d",&string,string,[string retainCount]);

    NSLog(@"6mutableCopy--retainStringP = %p,retainStringContentP=%p,retainCount = %d",&retainString,retainString,[retainString retainCount]);

    NSLog(@"6mutableCopy--retainString2P = %p,retainString2ContentP=%p,retainCount = %d",&retainString2,retainString2,[retainString2 retainCount]);

    NSLog(@"6mutableCopy--retainString3P = %p,retainString3ContentP=%p,retainCount = %d",&retainString3,retainString3,[retainString3 retainCount]);

    NSLog(@"6mutableCopy--retainString4P = %p,retainString4ContentP=%p,retainCount = %d",&retainString4,retainString4,[retainString4 retainCount]);

    /*

2015-04-09 15:06:04.923 BlockDemo[5621:60b] 6mutableCopy--stringP = 0xbfffc930,stringContentP=0x8e6e920,retainCount = 2

     2015-04-09 15:06:04.924 BlockDemo[5621:60b] 6mutableCopy--retainStringP = 0xbfffc92c,retainStringContentP=0x8e6e920,retainCount = 2

     2015-04-09 15:06:04.924 BlockDemo[5621:60b] 6mutableCopy--retainString2P = 0xbfffc928,retainString2ContentP=0x8e6e920,retainCount = 2

     2015-04-09 15:06:04.924 BlockDemo[5621:60b] 6mutableCopy--retainString3P = 0xbfffc924,retainString3ContentP=0x8e6e920,retainCount = 2

     2015-04-09 15:06:04.925 BlockDemo[5621:60b] 6mutableCopy--retainString4P = 0xbfffc920,retainString4ContentP=0x8e6f930,retainCount = 1

   */

//操作六：release  

    [retainString4 release];

    

    NSLog(@"7release--stringP = %p,stringContentP=%p,retainCount = %d",&string,string,[string retainCount]);

    NSLog(@"7release--retainStringP = %p,retainStringContentP=%p,retainCount = %d",&retainString,retainString,[retainString retainCount]);

    NSLog(@"7release--retainString2P = %p,retainString2ContentP=%p,retainCount = %d",&retainString2,retainString2,[retainString2 retainCount]);

    NSLog(@"7release--retainString3P = %p,retainString3ContentP=%p,retainCount = %d",&retainString3,retainString3,[retainString3 retainCount]);

//    NSLog(@"7mutableCopy--retainString4P = %p,retainString4ContentP=%p,retainCount = %d",&retainString4,retainString4,[retainString4 retainCount]);//此时对象已经不存在，release 会导致访问野指针，造成crash

    /*

     2015-04-09 15:06:04.925 BlockDemo[5621:60b] 7release--stringP = 0xbfffc930,stringContentP=0x8e6e920,retainCount = 2

     2015-04-09 15:06:04.926 BlockDemo[5621:60b] 7release--retainStringP = 0xbfffc92c,retainStringContentP=0x8e6e920,retainCount = 2

     2015-04-09 15:06:04.926 BlockDemo[5621:60b] 7release--retainString2P = 0xbfffc928,retainString2ContentP=0x8e6e920,retainCount = 2

     2015-04-09 15:06:04.926 BlockDemo[5621:60b] 7release--retainString3P = 0xbfffc924,retainString3ContentP=0x8e6e920,retainCount = 2

     (lldb)

     */