[OC Foundation框架 - 17] copy语法

 1         NSArray *arr1 = [NSArray arrayWithObjects:@"张三", @"李四", nil];
 2         NSLog(@"arr1.addr: %p", arr1); // 0x1002052b0
 3         NSLog(@"arr1.retainCount: %ld", arr1.retainCount); // 1
 4 
 5        
 6         NSArray *arr2 = [arr1 copy];
 7         NSLog(@"arr1.addr: %p", arr1); // 0x1002052b0
 8         NSLog(@"arr1.retainCount: %ld", arr1.retainCount); // 2  <-- 浅拷贝，相当于retain, retainCount+1
 9         NSLog(@"arr2.addr: %p", arr2); //0x1002052b0 <-- 浅拷贝，依旧指向同一个对象
10         NSLog(@"arr2.retainCount: %ld", arr2.retainCount); // 2 <-- 浅拷贝，还是原来对象的retainCount

 1         NSMutableArray *arr1 = [NSMutableArray array];
 2         [arr1 addObject:@"123"];
 3         [arr1 addObject:@"abc"];
 4         NSLog(@"arr1.addr: %p", arr1); // 0x100204840
 5         NSLog(@"arr1.retainCount: %ld", arr1.retainCount); // 1
 6        
 7        
 8         NSMutableArray *arr2 = [arr1 copy];
 9         NSLog(@"arr1.addr: %p", arr1); // 0x100204840
10         NSLog(@"arr1.retainCount: %ld", arr1.retainCount); // 1 <-- 深拷贝，原来的对象retainCount保持
11         NSLog(@"arr2.addr: %p", arr2); // 0x100300000 <-- 深拷贝，开辟了新的内存空间，拷贝出来的实际对象是NSArray
12         NSLog(@"arr2.retainCount: %ld", arr2.retainCount); // 1 <-- 深拷贝，新的对象retainCount独立

1         // 先创建出一个NSString对象，再用另一个指向
2         NSString *str1 = [NSString stringWithFormat:@"abc"];
3         NSLog(@"%ld", str1.retainCount); // -1
4         NSString *str2 = [NSString stringWithString:str1];
5         NSLog(@"%ld", str2.retainCount); // 1

 1         // 这里不能使用 NSMutableString *mstr1 = @"abc", 或者在延迟赋值 mstr1 = @"abc"; 否则同样指向常量池
 2         NSMutableString *mstr1 = [[NSMutableString alloc] initWithString:@"abc"];
 3         NSLog(@"mstr1.addr: %p", mstr1); // 0x100404990
 4         NSLog(@"mstr1.retainCount: %ld", mstr1.retainCount); // 1
 5 
 6 
 7         NSMutableString *mstr2 = [mstr1 copy];
 8         NSLog(@"mstr1.addr: %p", mstr1); // 0x100404990
 9         NSLog(@"mstr1.retainCount: %ld", mstr1.retainCount); // 1 <-- 深拷贝，原来的对象retainCount保持
10         NSLog(@"mstr2.addr: %p", mstr2); // 0x63626135 <-- 深拷贝，开辟了新的内存空间，但是指向的实际是一个字符串常量
11         NSLog(@"mstr2.retainCount: %ld", mstr2.retainCount); // -1 <-- 因为其实拷贝出来的是一个字符串常量

1         NSString *str1 = [[NSString alloc] initWithString:@"abc"];
2         NSLog(@"str1.addr: %p", str1); // 0x100001030
3         NSLog(@"str1.retainCount: %ld", str1.retainCount); // -1 <-- 字符串常量存在常量池，不使用堆内存
4 
5         NSMutableString *mstr2 = [str1 mutableCopy]; // mutableCopy 出来的是一个 NSMutableString 对象
6         NSLog(@"str1.addr: %p", str1); // 0x100001030
7         NSLog(@"str1.retainCount: %ld", str1.retainCount); // -1 <-- 对于字符串常量, 无论是copy, retain, release操作都不会改变retianCount
8         NSLog(@"mstr2.addr: %p", mstr2); // 0x100106460 <-- 深拷贝，开辟新的空间
9         NSLog(@"mstr2.retainCount: %ld", mstr2.retainCount); // 1 <-- 由于是NSMutableString对象，retainCount == 1

1         NSMutableString *mstr1 = [[NSMutableString alloc] initWithString:@"abc"];
2         NSLog(@"mstr1.addr: %p", mstr1); // 0x100402910
3         NSLog(@"mstr1.retainCount: %ld", mstr1.retainCount); // 1
4 
5         NSMutableString *mstr2 = [mstr1 mutableCopy]; // mutableCopy 出来的是一个 NSMutableString 对象
6         NSLog(@"mstr1.addr: %p", mstr1); // 0x100402910
7         NSLog(@"mstr1.retainCount: %ld", mstr1.retainCount); // 1
8         NSLog(@"mstr2.addr: %p", mstr2); // 0x100300e90 <-- 深拷贝，开辟新的空间
9         NSLog(@"mstr2.retainCount: %ld", mstr2.retainCount); // 1

1 @interface Student : NSObject
2 
3 //copy代表setter会release旧对象，copy新对象
4 @property (nonatomic, copy) NSString *name;
5 
6 @end

1 - (id)copyWithZone: (NSZone *) zone
2 {
3      Student *stu = [[Student allocWithZone:zone] init];
4      stu.name = self.name;
5      return stu;
6 }