Convert NSNumber to NSTimeInterval in Swift

Question

I'm stuck with some sort of casting in Swift as I am very new to Swift.

Here is my code:

 if let matchDateTime = item["matchDate"].number {
     _matchDateTime=matchDateTime
 }

 println(_matchDateTime)                      
 let date = NSDate(timeIntervalSince1970:_matchDateTime)

but its giving me the error:

Extra argument timeSinceInterval1970 in call

I don't know whats that error, may be convert NSNumber to NSTimeInterval but how? No idea.

Anyone who can help me out with this.

Thanks in advance.

Impartible

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Answer 1

NSTimeInterval is just a typedaliased Double.

Therefore casting from NSNumber to NSTimeInterval:

let myDouble = NSNumber(double: 1.0)
let myTimeInterval = NSTimeInterval(myDouble.doubleValue)

Edit: And the reverse is true.

let myTimeInterval = NSTimeInterval(1.0)
let myDouble = NSNumber(double: myTimeInterval)

Edit 2: As @DuncanC points out in the comments below, you can cast directly in the method call:

let date = NSDate(timeIntervalSince1970: NSTimeInterval(_matchDateTime))

Soupy

Swift is nicer about casting between NSNumber and scalar number types than Objective-C is, so you can also use the syntax Double(myDouble) or NSTimeInterval(myDouble) where myDouble is an NSNumber like in your answer. – Phonoscope

That's great that Swift handles that in a nicer way. I still prefer the above method as it is cleaner (IMO) and less likely to break with a new version of Swift (as it uses the established Cocoa API for NSNumber). – Soupy

Fair enough. I prefer the Swift style when working in Swift. Personal taste, I suppose. (And I think that changes to a core feature like type casting are exceedingly unlikely. That part of the language is well defined.) – Phonoscope

Answer 2

Try casting your NSNumber to a Double. This code works in a playground:

let aNumber: NSNumber = 1234567.89
let aDate = NSDate(timeIntervalSinceReferenceDate: Double(aNumber))

Phonoscope

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