Experimenting with MusicKit for Swift - Repeat Mode

• Exploring MusicKit

Exploring MusicKit

I wrote this book to fill in the gap for the documentation, filled with examples so that you do not have to spend time experimenting yourself.

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In MusicKit for Swift, Apple provides us with a MusicPlayer object that our app uses to play music. It has three kinds of enumerations -

• PlaybackStatus - The music player playback status modes.
• RepeatMode - The repeat modes for the music player.
• ShuffleMode - The shuffle modes for the music player.

In this post, we’ll explore RepeatMode, and how we can implement it in our app.

RepeatMode is an enum that contains three cases -

• all - Repeating the currently playing collection.
• none - In disabled state, and playback stops after the current item.
• one - Repeating the currently playing entry.

The MusicPlayer also exposes a State class, which is an ObservableObject. We observe the properties of the music player such as playbackStatus, playbackRate, repeatMode and shuffleMode.

If you take the example of Apple Music, there’s a repeat mode button that you can iterate through to repeat all the songs or a particular one. To create something similar in my app, Musadora, I extended MusicPlayer.RepeatMode to conform to CaseIterable. As I’m extending the enum outside the framework, it prevents automatic synthesis of ‘allCases’, a requirement of protocol CaseIterable. To fix that, I manually add a static variable to the extension -

public static var allCases: [MusicPlayer.RepeatMode] = [.none, .all, .one]

Now, I add a mutating function next() for circulation iteration of the options. It sets to the first element if it is the last one. Otherwise, increments to the next one.

mutating func next() {
    let allCases = Self.allCases
    let currentIndex = allCases.index(after: allCases.firstIndex(of: self)!)

    self = allCases[currentIndex == allCases.endIndex ? allCases.startIndex : currentIndex]
}

The extension looks like -

extension MusicPlayer.RepeatMode: CaseIterable {
    public static var allCases: [MusicPlayer.RepeatMode] = [.none, .all, .one]

    mutating func next() {
        let allCases = Self.allCases
        let currentIndex = allCases.index(after: allCases.firstIndex(of: self)!)

        self = allCases[currentIndex == allCases.endIndex ? allCases.startIndex : currentIndex]
    }
}

In the NowPlayingPrimaryControlsView , I observe the value of state -

@ObservedObject private var state = ApplicationMusicPlayer.shared.state

When the user taps on the repeat mode button, the next() method of the enum is called and based on the response, the image is changed.

Button(action: { state.repeatMode?.next() }) {
    Image(systemName: state.repeatMode == .one ? "repeat.1" : "repeat")
        .font(.title3)
        .padding(12)
        .background(state.repeatMode == MusicPlayer.RepeatMode.none ? nil : Circle().opacity(0.1))
}

Here’s how it looks -

Based on the value of the repeatMode, the MusicPlayer decides if the song is repeated or not.

You can similarly create the shuffle button as well!

Button(action: { state.shuffleMode?.next() }) {
    Image(systemName: "shuffle")
        .font(.title3)
        .padding(12)
        .background(state.shuffleMode == .songs ? Circle().opacity(0.1) : nil)
}