Stop crashing when AVAudioPlayer URL is nil? - swift

Question

I'm still a beginner in coding but I'm working on a very basic music player to get an idea of how Swift works.
////Functions
//Play chosen file function
func playChosenFile() {
//Set up the music file URL.
let musicFilePathURL = MenuBarModel.mainMenu.URL
if musicFilePathURL != nil {
//Initialize audioPlayer with safety.
do {
try audioPlayer = AVAudioPlayer(contentsOfURL: musicFilePathURL!)
}
catch {
}
}
else if musicFilePathURL == nil {
//Some code that will make the player do nothing.
}
}
//Play function
func play() {
playChosenFile()
audioPlayer.play()
}
So musicFilePathURL gets initialized with a URL if I choose an audio file using NSOpenPanel().
If I do select a file using NSOpenPanel(), then musicFilePathURL has the location of the selected file and is then passed to AVAudioPlayer. Once I press the Play button, the function "play()" executes and then it executes playChosenFile() and audioPlayer.play().
The music player plays the song if I do this before pressing the play button.
If I press the play button before selecting any file to play, then the program crashes because musicFilePathURL is nil.
I'm confused on how to make the program not crash if there is no file selected before pressing the play button. As an example, if you open VLC, if you press the Play button, it prompts to pick a file, but if you decide to press cancel, the player does nothing.
How can I make my program do nothing if I press the play button with no audio file picked at startup?

Answer 1

You've got the right idea with the try/catch statements for the Audio Player, but you could probably use another one in the play() function.
That way when the audioPlayer attempts to play a null object, an exception will be caught and you can process it handle it on your own rather than having the app crash.
Perhaps something like this? I would try it, but unfortunately I left my Mac at home.
func play(){
do {
playChosenFile()
audioPlayer.play()
} catch {
print "Error Occurred (Did the user specify a file?)
}
}