Get unique artist names from MPMediaQuery - iphone

Question

I am using MPMediaQuery to get all artists from library. Its returning unique names I guess but the problem is I have artists in my library like "Alice In Chains" and "Alice In Chains ". The second "Alice In Chains" has some white spaces at the end, so it returns both. I dont want that. Heres the code...
MPMediaQuery *query=[MPMediaQuery artistsQuery];
NSArray *artists=[query collections];
artistNames=[[NSMutableArray alloc]init];
for(MPMediaItemCollection *collection in artists)
{
MPMediaItem *item=[collection representativeItem];
[artistNames addObject:[item valueForProperty:MPMediaItemPropertyArtist]];
}
uniqueNames=[[NSMutableArray alloc]init];
for(id object in artistNames)
{
if(![uniqueNames containsObject:object])
{
[uniqueNames addObject:object];
}
}
Any ideas?

Answer 1

One possible workaround would be to test the artist names for leading and/or trailing whitespace. You could inspect the first and last character of the string for membership with NSCharacterSet whitespaceCharacterSet. If true, then trim all leading and/or trailing whitespace using the NSString stringByTrimmingCharactersInSet method. Then you could add either the trimmed string or the original string to a NSMutableOrderedSet. The ordered set will only accept distinct objects so no duplicate artist names will be added:
MPMediaQuery *query=[MPMediaQuery artistsQuery];
NSArray *artists=[query collections];
NSMutableOrderedSet *orderedArtistSet = [NSMutableOrderedSet orderedSet];
for(MPMediaItemCollection *collection in artists)
{
NSString *artistTitle = [[collection representativeItem] valueForProperty:MPMediaItemPropertyArtist];
unichar firstCharacter = [artistTitle characterAtIndex:0];
unichar lastCharacter = [artistTitle characterAtIndex:[artistTitle length] - 1];
if ([[NSCharacterSet whitespaceCharacterSet] characterIsMember:firstCharacter] ||
[[NSCharacterSet whitespaceCharacterSet] characterIsMember:lastCharacter]) {
NSLog(#"\"%#\" has whitespace!", artistTitle);
NSString *trimmedArtistTitle = [artistTitle stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceCharacterSet]];
[orderedArtistSet addObject:trimmedArtistTitle];
} else { // No whitespace
[orderedArtistSet addObject:artistTitle];
}
}
You can also return an array from the ordered set if you need it:
NSArray *arrayFromOrderedSet = [orderedArtistSet array];