更改对象从NSUserDefaults获取

Question

我想从NSUserDefaults更改对象get.
但是在执行以下代码时,应用程序崩溃并显示错误消息:

*** Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: '-[__NSCFDictionary setObject:forKey:]: mutating method sent to immutable object’

我有这个代码.

NSUserDefaults* pref = [NSUserDefaults standardUserDefaults];
NSMutableArray* data = [[NSMutableArray alloc]init];
data = [[pref objectForKey:@"Data"] mutableCopy];

for (NSArray* array in data) { //make object mutable
        [array mutableCopy];
        for (NSDictionary* dic in array) {
            [dic mutableCopy];
        }
    }

[data[0][1] setObject:@"YES" forKey:@"isChecked"]; //for example

[pref setObject: data forKey: @"Data"];
[pref synchronize];

数据结构:

NSMutableArray* arr1 = [@[[@{@"name":@"abc", @"isChecked":@"YES"} mutableCopy], [@{@"name":@"def", @"isChecked":@"NO"} mutableCopy]] mutableCopy];
NSMutableArray* arr2 = [@[[@{@"name":@"ghi", @"isChecked":@"NO"} mutableCopy], [@{@"name":@"jkl", @"isChecked":@"YES"} mutableCopy]] mutableCopy];
NSMutableArray* data = [@[arr1, arr2] mutableCopy];
[userDefaults setObject: data forKey: @"Data"];

如何修复它以更改对象NSArray或NSDictionary从中获取对象NSUserDefaults？

Answer 1

你有正确的想法 - 返回的对象NSUserDefaults是不可变的,你需要mutableCopy用来获得一个可变的副本.但是,您的实施存在缺陷.

mutableCopy返回一个新的,可变的对象副本.它不会使现有对象变得可变.您只是忽略了您正在创建的可变副本.

由于您希望改变数组中的数据,因此无法使用枚举,或者在枚举时会出现对象被突变的错误,因此您需要通过索引访问数组 -

NSUserDefaults* pref = [NSUserDefaults standardUserDefaults];
NSMutableArray* data = [[pref objectForKey:@"Data"] mutableCopy]; 

for (int i=0;i<data.count;i++) { 
    NSMutableArray *mArray = [data[i] mutableCopy];
    for (int j=0;j<mArray.count;j++) {
        NSMutableDictionary *mDictionary=[mArray[j] mutableCopy];
        mDictionary[@"SomeKey"]=@"SomeValue";
        mArray[j]=mDictionary;
    }
    data[i]=mArray;
}

[userDefaults setObject: data forKey: @"Data"];