PDKTimer

A simple swift GCD based Timer

Why?

Why do we need a new timer if we already have NSTimer?

NSTimer is an Objective-C class that needs a @selector to call. As in swift, we don’t have selectors, whe have to pass a String with the name of the function we want to be called. Something like :

let timer = NSTimer(timeInterval: 0.5, target: self, selector: "myfunction", userInfo: nil, repeats: false)

Yikes!

The problem with that is that myfunction string will be evaluated in run-time. That means we would make a typo in the name of the function and the compiler won’t be able to tell us that code won’t execute.

Wouldn’t it be nice if whe could pass a closure to the timer?

How to use it

Using PDKTimer is really easy. Simply call

let timer = PDKTimer(timeInterval: 5.0, repeats: true){
    // do something
}

and that closure will be executed each 5 seconds

Note (Scheduling):

PDKTimer instances don’t do auto schedule. You have to manually call schedule in order to start.

let timer = PDKTimer(timeInterval: 5.0, repeats: true){
    // do something
}
timer.schedule()

GCD powered

PDKTimer is implemented using GCD APIs. It isn’t a Swift wrapper that uses NSTimer on the inside. This allows not only executing the timer in a background queue, but dispatching the timed closure on a specific dispatch queue. Simply create your timer using :

let dispatchQueue = dispatch_queue_create("com.produkt.pdktimer.test", DISPATCH_QUEUE_SERIAL)
PDKTimer(timeInterval: 0.5, repeats: false, dispatchQueue: dispatchQueue){
    // do something
}

and your closure will be executed on your custom queue

Syntax sugar

I really liked SwiftyTimer API from radex, that is a Swift wrapper for NSTimer So I adopted the API that he suggests.

You can create repeating and non-repeating timers with PDKTimer.every and PDKTimer.after short-hand initializers

PDKTimer.every(5.seconds){
    // executes every 5 seconds
}

PDKTimer.after(5.seconds){
    // waits 5 seconds and then executes once
}

An extension of Double is also defined so you can define time intervals with Ruby-on-Rails-like helpers

500.milliseconds
1.second
2.5.seconds
5.seconds
10.minutes
1.hour

Note (Scheduling):

PDKTimer short-hand initializers do auto schedule. So you don’t need to manually call schedule

PDKTimer.every(5.seconds){

}
// no scheduling needed

Author

Daniel García

https://github.com/fillito https://github.com/Produkt

Thanks

Thanks to Javi Soto for writing MSWeakTimer. It helped me a lot understanding som GCD APIs to implement a timer

Thanks to Radek Pietruszewski for designing SwiftyTimer API, that I basically ripped off