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Using NSTimer in Swift

I use an NSTimer for blinking purposes. As I converted my old code I came across this line:

    // Start the timer if it is not active already.
    if (!blinkTimer)
        blinkTimer = [NSTimer scheduledTimerWithTimeInterval:0.5


My first idea to replace this code was as follows (this seems natural when you use code completion):

        if blinkTimer == nil {
            blinkTimer = NSTimer(timeInterval: 0.5, target: self, selector: "blinkCursorPositionMarker:", userInfo: nil, repeats: true)

But that actually won't work. The timer will not fire. The problem is that the replacement code is not the same as the original code. The Objective-c code uses a factory (class function) to create a timer while the Swift code instantiates a timer itself.
Turns out that when we create a timer ourselves, we also have to assign it to a run loop. Which is not all that difficult, that can be done as follows:

            blinkTimer = NSTimer(timeInterval: 0.5, target: self, selector: "blinkCursorPositionMarker:", userInfo: nil, repeats: true)
            NSRunLoop.mainRunLoop().addTimer(blinkTimer, forMode: NSDefaultRunLoopMode)

But why go through that if the same factory function is available in Swift? The following solution shows the usage of the factory:

        if blinkTimer == nil {
            blinkTimer = NSTimer.scheduledTimerWithTimeInterval(0.5, target: self, selector: "blinkCursorPositionMarker:", userInfo: nil, repeats: true)

This code is now the same as the Objective-C code, and the created timer is immediately assigned to the run-loop.

Lesson to self: be careful when replacing a factory function with an object instantiation!

Happy coding...

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