Can't set MPMusicPlayerController queue with MPMusicPlayerMediaItemQueueDescriptor

Question

This code results in silence:

let query = MPMediaQuery.songs()
let result = query.items
guard let items = result, items.count > 0 else {return}
let song = ite         


        

Answer 1

You've found a bug. It appears that the initializer MPMusicPlayerMediaItemQueueDescriptor(itemCollection:) is completely broken: it results in an unusable queue descriptor.

The workaround, where possible, is to use the other initializer instead, namely MPMusicPlayerMediaItemQueueDescriptor(query:).

For example, in this case, you could write (picking up in the last four lines of the original code):

let coll = MPMediaItemCollection(items: [song])
let predicate = MPMediaPropertyPredicate(
                value: song.persistentID,
                forProperty: MPMediaItemPropertyPersistentID)
let query = MPMediaQuery(filterPredicates: [predicate])
let q = MPMusicPlayerMediaItemQueueDescriptor(query: query)
player.setQueue(with: q)
player.play()

Unfortunately, there are many circumstances where you can't form a single query that gets the MPMediaItemCollection you really wanted.

In this particular example you could work around that, too, by setting the player's queue directly with an MPMediaItemCollection instead of a MPMusicPlayerMediaItemQueueDescriptor made from an MPMediaItemCollection.

But alas, there are some commands (such as append(_:)) that require an MPMusicPlayerMediaItemQueueDescriptor, and for things like that, this entire API is basically hosed. It has been hosed since iOS 10.1 and it remains hosed in iOS 11.1.