Try and Catch with NSUrl(fileURLWithPath) - ios

Question

I've been trying to implement try and catch in the following code
if let s = songId {
let track: NSURL!
track = NSURL(fileURLWithPath: NSBundle.mainBundle().pathForResource(s, ofType: "mp3")!)
.............
}
I came up with the following code:
do {
track = try NSURL(fileURLWithPath: NSBundle.mainBundle().pathForResource(s, ofType: "mp3")!)
}
catch let error as NSError {
print("NSURL Error: \(error.localizedDescription)")
}
But I get the following warnings:
No calls to throwing functions occur within 'try' expression
and
'catch' block is unreachable because no errors are thrown in 'do' block
And this is strange to me, because this construction usually works.
Only with NSURL this construction isn't working. And I can't figure out why this is happening. Maybe it has something to do with it being an optional, but im not sure.
I can't figure out how to solve this. I need to use a try/catch or something similar, but I can't figure it out how to make it work.
I saw some similar problems on Google, but it didnt gave me an answer.
So my question is: How can I implement a try/catch construction or something similar with NSURL?
Thanks in advance.

Answer 1

There are no methods used that marked with throws keyword at the definition. So it really does not make much sense to wrap your code with try-catch. I would recommend to consider this:
let s = "song"
guard let trackURL = NSBundle.mainBundle().URLForResource(s, withExtension: "mp3") else {
print("File not found in the app bundle: \(s).mp3")
return false
}
Does it help?

Answer 2

That initializer doesn't fail and doesn't throw or fail so a try/catch block is unnecessary. The declaration is:
public init(fileURLWithPath path: String)
If it could throw an error is would be declared as:
public init(fileURLWithPath path: String) throws
Or if it might fail without throwing an error it would be declared as:
public init?(fileURLWithPath path: String)
If you're certain that the bundle will always contain the track you're looking for then you can just use
let track = NSURL(fileURLWithPath: NSBundle.mainBundle().pathForResource(s, ofType: "mp3")!)