ObjectiveC 深浅拷贝

/*****************************************
         *
         * 非容器类对象
         *
         *****************************************/
        
        /*mstr和mstrCopy指向的是同一块内存区域，我们称之为弱引用（weak reference）。而mstrMCopy是真正的复制，
         系统为其分配了新内存空间，保存从mstr复制过来的字符串值*/
        
        NSMutableString *mstr = [NSMutableString stringWithString:@"origin"];
        NSMutableString *mstrCopy = [mstr copy];
        NSMutableString *mstrMCopy = [mstr mutableCopy];
        
        NSLog(@"mstr is %@",mstr);
        NSLog(@"mstrCopy is %@",mstrCopy);
        NSLog(@"mstrMCopy is %@",mstrMCopy);
        NSLog(@"*****************************");
        
        /*mstrCopy它所指向的其实是一个imutable对象，是不可改变的，所以会出错*/
        [mstr appendString:@"111"];
        //[mstrCopy appendString:@"222"]; //Error
        [mstrMCopy appendString:@"333"];
        
        NSLog(@"mstr is %@",mstr);
        NSLog(@"mstrCopy is %@",mstrCopy);
        NSLog(@"mstrMCopy is %@",mstrMCopy);
        NSLog(@"*****************************");
        
        /*****************************************
         *
         * 容器类对象
         *
         *****************************************/
        
        /*arrayCopy1是和array指向相同的对象,包括array里面的元素也是指向相同的指针*/
        NSArray *array1     = [NSArray arrayWithObjects:@"a",@"b",@"c",nil];
        NSArray *arrayCopy1 = [array1 copy];
        NSLog(@"array1 retain count: %d",(int)[array1 retainCount]);
        NSLog(@"array1 retain count: %d",(int)[arrayCopy1 retainCount]);
        NSLog(@"array1 %@",array1);
        NSLog(@"arrayCopy1 %@",arrayCopy1);
        
        /*mArrayCopy1是array1的可变副本，指向的对象和array1不同，但是其中的元素和array1中的元素指向的还是同一个对象。
         mArrayCopy1还可以修改自己的对象*/
        NSMutableArray *mArrayCopy1 = [array1 mutableCopy];
        [mArrayCopy1 addObject:@"de"];
        [mArrayCopy1 removeObjectAtIndex:0];
        NSLog(@"mArrayCopy1 %@",mArrayCopy1);