如何在 NSUserDefaults 中存储多个 NSMutableDictionary

Question

我正在尝试在 NSUserDefaults 中存储多个 NSMutableDictionary 我试过这个：

-(void)storeNotification:(NSDictionary*)dict{
    NSMutableDictionary *dic = [dict mutableCopy];
    //add read object to dic
    [dic setObject:@"NO" forKey:@"read"];

    //get stored arrayofdics
    NSMutableArray *arrayofdics = [[NSUserDefaults standardUserDefaults] objectForKey:@"arrayofdics"];
    if([arrayofdics count] == 0){
        arrayofdics = [[NSMutableArray alloc] init];
    }

    //add dic to arrayofdics
    [arrayofdics addObject:dic];

    //store arrayofdics
    [[NSUserDefaults standardUserDefaults] setObject:arrayofdics forKey:@"arrayofdics"];
    NSLog(@"stored: %@", arrayofdics);
}

这样我就可以像这样修改 dic 中的 read 键：

-(void)markAsRead:(int)dic_index{
    NSMutableArray *arrayofdics = [[NSUserDefaults standardUserDefaults] objectForKey:@"arrayofdics"];
    NSMutableDictionary *dic = [arrayofdics objectAtIndex:dic_index];
    [dic setObject:@"YES" forKey:@"read"];
    [arrayofdics replaceObjectAtIndex:dic_index withObject:dic];
    [[NSUserDefaults standardUserDefaults] setObject:arrayofdics forKey:@"arrayofdics"];
}

并且还能够迭代所有 storeNotifications

日志显示：

已存储：( { 阅读=否； ... })

但是当第二次调用storeNotification时我得到一个错误：

Printing description of arrayofdics->isa:
(Class) isa = __NSCFArray
(lldb)

这意味着数组没有正确存储。任何想法为什么？或者如何更好地做到这一点？

Answer 1

此错误是由于在不可变对象中调用可变函数造成的

Userdefaults 总是 return 不可变对象。因此，当您从 userdefaults 获取对象时，请使其可变。

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

如何在 NSUserDefaults 中存储多个 NSMutableDictionary

How to store multiple NSMutableDictionarys in NSUserDefaults

macos

cocoa

objective-c

nsmutablearray

nsmutabledictionary