Question

Hello everyone please guide me something.

I am doing custom music app with iPodMusicPlayer.

Here is some of code i load songs from iPodLibrary.

MPMediaQuery *query = [MPMediaQuery playlistsQuery];

        MPMediaPropertyPredicate *filter = [MPMediaPropertyPredicate predicateWithValue:self.playlistName forProperty:MPMediaPlaylistPropertyName comparisonType:MPMediaPredicateComparisonContains];

        [query addFilterPredicate:filter];      

**self.app.arrayFromAppDelegate = (NSMutableArray *)[query items];**


        self.userMediaItemCollection = [[MPMediaItemCollection alloc] initWithItems:self.app.arrayFromAppDelegate];

        [self.player setQueueWithItemCollection:self.userMediaItemCollection];

according to above code

self.app.arrayFromAppDelegate = (NSMutableArray *)[query items];

arrayFromAppDelegate is a NSMutableArray that i declared in AppDelegate.
[query items]; return NSArray and i added to NSMutableArray with pointer(NSMutableArray *)

Is that right way when i used like that?

or should i use like self.app.arrayFromAppDelegate = [[query items] mutableCopy];

Which way is the best for memory and do i need to use removeAllObject after use mutableCopy?

Please guide me.

sorry for my bad english.

Thanks you for your help.

Answer 1

If you’re going from NSArray to NSMutableArray don’t just cast it, use the mutable copy.