检查NSUserDefault中是否已存在NSString / NSMutableArray？

Question

I'm making this app with a tableview and stuff. I want to make a "Favorites"-tab, and in the detail-view I want to make a star-like button. I'm done with the "add to favorites" stuff and want to make it impossible to add a string to my favoriteViewController more than once.

Basically, I want to check if my NSUserDefaults contains a certain string in its NSMutableArray that matches the indexPath.row in the table view. It's really hard to explain...

Here's a snippet out of the code. I want to check if the "indexPathRowString" already exists in favoriteKey, before adding it again.

-(IBAction)addToFavorite:(id)sender {
    NSMutableArray* alreadyFavourites = [[[NSUserDefaults standardUserDefaults] objectForKey:@"favoriteKey"] mutableCopy];
    [favoritedAlready addObject:indexPathRowString];
    [[NSUserDefaults standardUserDefaults] setObject:alreadyFavourites forKey:@"favoriteKey"];
    [[NSUserDefaults standardUserDefaults] synchronize];
}

I'm very thankful for answers, I really need to fix this! :)

Answer 1

You want NSArray's containsObject: .

Because NSString implements the NSObject Protocol method isEqual: to return YES for two strings of the same content, this method will work correctly for you with two different string objects of the same value.

Answer 2

you can check using

if (![favoritedAlready containsObject:indexPathRowString])
{
    [favoritedAlready addObject:indexPathRowString];
}