Question

您好我正在尝试将数组存储到NSUserDefaults中，但我遇到了麻烦。该方法接受一个NSDictionary，我将存储到一个数组中，我将存储到NSUSerDefaults中。问题是当我创建一个mutableCopy它说它是一个字典而不是NSMutable数组类型？这个方法是我第一次调用NSUserDefaults所以我不确定为什么会发生错误？这是代码谢谢

+(void) getRecentPhoto:(NSDictionary *)recentPhoto{

NSUserDefaults* defaults = [NSUserDefaults standardUserDefaults];
 //stores it as a dictionary? error happens here
NSMutableArray* recentPhotos = [[defaults objectForKey:@"recentPhoto"] mutableCopy];
NSLog(@"%@", [recentPhotos class]);
if(!recentPhotos) recentPhotos = [NSMutableArray array];
BOOL copy = NO;

//these will crash the program
NSLog(@"%@", [[recentPhotos objectAtIndex:0] objectForKey:@"id"]);
NSLog(@"%@", [recentPhoto objectForKey:@"id"]);

 //this checks if it has been stored before by using an id key
for(int i =0; i < [recentPhotos count]; i++){

    if ([[[recentPhotos objectAtIndex:i] objectForKey:@"id"] isEqualToString:[recentPhoto objectForKey:@"id"]] ) {
        copy = YES;
    }
}
if(copy ==NO)
[recentPhotos addObject:recentPhoto];
[defaults setObject:recentPhoto forKey:@"recentPhoto"];
[defaults synchronize];


}

这是错误

 NSInvalidArgumentException', reason: '-[__NSCFDictionary objectAtIndex:]: unrecognized selector

Answer 1

我认为问题在于，在此方法的最后，您尝试将recentPhoto（一个字典）存储到用户默认值而不是recentPhotos，即您要存储的可变数组。

实际上，我认为在第一次调用此方法时它不会崩溃，因为recentPhoto尚未存储在用户默认值中。但在那之后，它会。

NSUserDefaults和存储值

1 个答案: