Question

我是ios编程的新手，上个月刚开始学习这个。

过去两天我遇到了一个问题。我无法弄明白如何自己解决这个问题。

所以，我想请你帮我解决这个问题！

这是我得到的错误。

[__NSCFDictionary setObject:forKey:]: mutating method sent to immutable object'

我了解到我收到此错误，因为我从NSUserDefaults获取的对象始终是不可变的。

所以，我mutableCopy我要添加新对象的数组。

    NSMutableArray *temporaryArray = [users[1][@"users"] mutableCopy];
    [temporaryArray addObject:myData];

    users[1][@"users"] = temporaryArray;

但是，在上面的第三行，当然会导致同样的错误。

我知道它导致此错误的原因，但我不知道如何编码来解决此问题。我认为解决方案非常简单和基本，但我无法弄清楚如何。

如果有人帮我解决这个问题我很感激!!

非常感谢你！

- (void)saveData
{

    NSUserDefaults *userDefaults = [NSUserDefaults standardUserDefaults];
    NSMutableArray *users = [userDefaults objectForKey:@"users"];

    NSDictionary *myData = @{@"name":@"test", @"birthdate":@"1981-01-01", @"sex":@"male"};

    NSMutableArray *temporaryArray = [users[1][@"users"] mutableCopy];
    [temporaryArray addObject:myData];

    users[1][@"users"] = temporaryArray;



    [userDefaults setObject:users forKey:@"users"];
    [userDefaults synchronize];

    [self.target performSelector:self.action withObject:@"test.png"];

    [self dismissViewControllerAnimated:YES completion:nil];

}

“user”数组的结构。

(
    {
    label = "\U81ea\U5206";
    users =         (
                    {
            birthdate = "2013-10-12";
            name = Test;
            sex = "\U7537\U6027";
        }
    );
},
    {
    label = "Family(\U5bb6\U65cf)";
    users =         (
    );
},
    {
    label = "Friends(\U53cb\U9054)";
    users =         (
    );
}
)

Answer 1

您获得的数组users不是可变副本：

NSMutableArray *users = [userDefaults objectForKey:@"users"];

您对同一个数组使用temporaryArray，temporary和testArray？错字？我想你想要的是：

NSUserDefaults *userDefaults = [NSUserDefaults standardUserDefaults];
NSMutableArray *users = [[userDefaults objectForKey:@"users"] mutableCopy];

NSDictionary *myData = @{@"name":@"test", @"birthdate":@"1981-01-01", @"sex":@"male"};

NSMutableArray *usersNested = [users[1][@"users"] mutableCopy];
[usersNested addObject:myData];
[users replaceObjectAtIndex:1 withObject:usersNested];

[userDefaults setObject:users forKey:@"users"];
[userDefaults synchronize];

Answer 2

您正在尝试改变不可变字典，该字典是数组的对象之一。

尝试以下方法：

- (void)saveData
{

    NSUserDefaults *userDefaults = [NSUserDefaults standardUserDefaults];
    NSMutableArray *users = [[userDefaults objectForKey:@"users"] mutableCopy];

    NSDictionary *myData = @{@"name":@"test", @"birthdate":@"1981-01-01", @"sex":@"male"};

    //Create a mutable copy of the dictionary object at index 1.
    NSMutableDictionary* mutableUsers = [users[1] mutableCopy]

    NSMutableArray *temporaryArray = [mutableUsers[@"users"] mutableCopy];
    [temporaryArray addObject:myData];
    mutableUsers[@"users"] = [temporaryArray copy];

    //Replace the dictionary with an immutable copy of the new dictionary.
    users[1] = [mutableUsers copy];

    [userDefaults setObject:users forKey:@"users"];
    [userDefaults synchronize];

    [self.target performSelector:self.action withObject:@"test.png"];

    [self dismissViewControllerAnimated:YES completion:nil];

}

处理从NSUserDefaults返回的对象时遇到问题

2 个答案: