Welcome to the Treehouse Community

The Treehouse Community is a meeting place for developers, designers, and programmers of all backgrounds and skill levels to get support. Collaborate here on code errors or bugs that you need feedback on, or asking for an extra set of eyes on your latest project. Join thousands of Treehouse students and alumni in the community today. (Note: Only Treehouse students can comment or ask questions, but non-students are welcome to browse our conversations.)

Looking to learn something new?

Treehouse offers a seven day free trial for new students. Get access to thousands of hours of content and a supportive community. Start your free trial today.

iOS Build a Playlist Browser with Swift Building the Music Library and Playlist Models Using a Playlist Instance

why I have to use as! instead of as in swift


I don't know if its a new rule in swift but my xcode always make me change as for as! when casting. I just click on fix-it otherwise won't run my app. It says that is necessary to downcast the value. Why in the videos appear like "as" and I have to use as!


Kevin Gonzales
Kevin Gonzales
4,638 Points

as is now as! since they updated it. hope that helped! I was confused too.

1 Answer

Kevin D
Kevin D
8,646 Points

I'm having the same issue. Xcode is telling me to change 'as' to 'as!' and my code doesn't run because of this.

Any ideas?

This is the code:

init(index: Int) {
    let musicLibrary = MusicLibrary().library
    let playlistDictionary = musicLibrary[index]

    title = playlistDictionary["title"] as String! // <-- these 'as' sections are causing a problem //
    description = playlistDictionary["description"] as String! // <-- //

    let iconName = playlistDictionary["icon"] as String! // <-- //
    icon = UIImage(named: iconName)

    let largeIconName = playlistDictionary["largeIcone"] as String! // <-- //
    largeIcon = UIImage(named: largeIconName)

    artists += playlistDictionary["artists"] as [String] // <-- //

    let colorsDictionary = playlistDictionary["backgroundColor"] as [String:CGFloat] // <-- //
    backgroundColor = rgbColorFromDictionary(colorsDictionary)


error message: "fatal error: unexpectedly found nil while unwrapping an Optional value"


Just realised I misspelled "largeIcon" in line 11. fixed it now!

Kevin Gonzales
Kevin Gonzales
4,638 Points

as is now as! since they updated it