Copy & MutableCopy

最近发现深浅拷贝居然记不清了，特地来温习下。

测试代码

- (void)testDictionary {
    NSDictionary *dicImmutable = [NSDictionary dictionaryWithObjectsAndKeys:@"lhe", @"name", nil];
    //    NSDictionary *dicImmutable = @{@"name":@"lhe"};
    NSMutableDictionary *dicMutable = [NSMutableDictionary dictionaryWithObjectsAndKeys:@"18", @"age", nil];
    
    NSMutableDictionary *dicCopy = [dicMutable copy];
    NSMutableDictionary *dicMutableCopy = [dicMutable mutableCopy];
    
    NSLog(@"类型：\n dicImmutable = %@, dicCopy = %@, dicMutableCopy = %@, dicMutable = %@", [dicImmutable class], [dicCopy class], [dicMutableCopy class], [dicMutable class]);
    NSLog(@"指针：\n dicImmutable = %p, dicCopy = %p, dicMutableCopy = %p, dicMutable = %p", dicImmutable, dicCopy, dicMutableCopy, dicMutable);
    NSLog(@"dicMutable.value = %@, dicCopy.value = %@, dicMutableCopy.value = %@", dicMutable[@"age"], dicCopy[@"age"], dicMutableCopy[@"age"]);
    NSLog(@"dicMutable.value = %p, dicCopy.value = %p, dicMutableCopy.value = %p", dicMutable[@"age"], dicCopy[@"age"], dicMutableCopy[@"age"]);
    //    [dicImmutable setValue:@"dfsdf" forKey:@"name"];
    
}
- (void)testArray {
    NSArray *arrImmutable = [NSArray arrayWithObjects:@"hello", @"world", nil];
    NSMutableArray *arrMutable = [NSMutableArray arrayWithObjects:@"s", @"d", @"r", nil];
    NSMutableArray *arrCopy = [arrMutable copy];
    NSMutableArray *arrMutableCopy = [arrMutable mutableCopy];
    
    NSLog(@"类型：\n arrImmutable = %@, arrCopy = %@, arrMutableCopy = %@, arrMutable = %@", [arrImmutable class], [arrCopy class], [arrMutableCopy class], [arrMutable class]);
    NSLog(@"指针：\n arrImmutable = %p, arrCopy = %p, arrMutableCopy = %p, arrMutable = %p", arrImmutable, arrCopy, arrMutableCopy, arrMutable);
    
//    [arr2 addObject:@"lhe"];
//    [arr3 addObject:@"lh"];
}
- (void)testString {
    NSString *nameImmutable = @"slg";//[NSString stringWithFormat:@"%@", @"slj"];
    NSMutableString *nameMutable = [NSMutableString stringWithString:@"lhe"];
    
    NSMutableString *nameCopy = [nameImmutable copy];
    NSMutableString *nameMutableCopy = [nameImmutable mutableCopy];
    
    NSLog(@"类型：\n nameImmutable = %@, nameCopy = %@, nameMutableCopy = %@, nameMutable = %@", [nameImmutable class], [nameCopy class], [nameMutableCopy class], [nameMutable class]);
    NSLog(@"指针：\n nameImmutable = %p, nameCopy = %p, nameMutableCopy = %p, nameMutable = %p", nameImmutable, nameCopy, nameMutableCopy, nameMutable);
    
//    [nameCopy appendString:@"++"];
//    NSLog(@"修改后的name == %@", nameCopy);
}

结果

总结

具体的类型跟创建的方式有关。

• 不可变类型
  • copy是指针拷贝，不可变类型。
  • mutableCopy是内容拷贝，变成了可变类型。
• 可变类型
  • copy是内容拷贝，可变类型。
  • mutableCopy是内容拷贝，可变类型。

1. 只有不可变类型的copy是浅拷贝，结果仍为不可变类型。
2. 不可变类型的mutableCopy，和可变类型的copy与mutableCopy都是深拷贝，结果都是可变类型。
3. 容器类的深拷贝是这个容器本身的复制，其内元素仍然是指针复制。
4. 使用归解档可以实现真正的深拷贝。