iphone - 当副本更改时 NSDictionary 也会更改

Question

我是 ObjectiveC 和 Xcode 的新手，并且会犯错误。这段代码从 getAllRecords 获取一个字典 (myDataPlist)。然后，我在 (myDataPlist) 中制作字典(1 条记录)的可变副本，并用它解密 1 个字段。这非常有效。我只返回该记录(mutCopy)。这也有效。我的问题是原始字典(myDataPlist)发生了变化。它解密的记录也在(myDataPlist)中解密。 2 NSLog(@"%@",myDataPlist) 返回不同的结果。我肯定错过了什么。为什么 (myDataPlist) 发生变化？

感谢您的帮助。

-(NSDictionary *)getRecordForKey:(NSString *)key{

    NSDictionary *myDataPlist = [self getAllRecords];
    NSMutableDictionary *mutCopy = [[myDataPlist valueForKey:key] mutableCopy];
    NSArray *keys = [mutCopy allKeys];
    NSData *tData = [[NSData alloc]init];
    NSLog(@"%@",myDataPlist);
    for (int x = 0; x <= [keys count] - 1; x++) {
        if (![keys[x] isEqualToString:@"Template"] && ![keys[x] isEqualToString:@"RecNum"]) {

        NSMutableArray *myArray = [mutCopy objectForKey:keys[x]];
        tData = myArray[1];
        NSString *tString = [tData decryptData:tData withKey:self.settingsManager.masterPad];
        myArray[1] = tString;
        [mutCopy setObject:myArray forKey:keys[x]];

        }
    }
    NSLog(@"%@",myDataPlist);
    return mutCopy ;
}

Answer 1

mutableCopy 仅创建字典的副本，而不创建其内容。因此，您从 [[myDataPlist valueForKey:key] mutableCopy] 收到的字典本质上是一个新字典，其中引用了相同的对象(它不是深拷贝)。

尝试使用

NSMutableDictionary *mutCopy = 
    [[NSMutableDictionary alloc] initWithDictionary:[myDataPlist valueForKey:key] 
                                          copyItems:YES];

而不是mutableCopy。

摘自苹果文档:

otherDictionary

A dictionary containing the keys and values with which to initialize the new dictionary.

flag

If YES, each object in otherDictionary receives a copyWithZone: message to create a copy of the object—objects must conform to the NSCopying protocol. In a managed memory environment, this is instead of the retain message the object would otherwise receive. The object copy is then added to the returned dictionary. If NO, then in a managed memory environment each object in otherDictionary simply receives a retain message when it is added to the returned dictionary.

如果您的字典包含自定义对象，请确保它们符合 NSCopying 协议(protocol)。