I just got real tired of dispatch_async...

Async.swift

//
//  Async.swift
//
//  Used as: Async().delay(2).onBackground({ ... }).onMainThread({ ... }).start()
//
//  Created by Arasthel on 22/04/15.
//  Copyright (c) 2015 Arasthel. All rights reserved.
//

import Foundation

class Async {
    
    private var onBackgroundClosure : (() -> Void)?
    private var onMainThreadClosure : (() -> Void)?
    private var delay : Float = 0
    
    init() {
        
    }
    
    func onBackground(closure : (() -> Void)) -> Async {
        onBackgroundClosure = closure
        return self
    }
    
    func onMainThread(closure : (() -> Void)) -> Async {
        onMainThreadClosure = closure
        return self
    }
    
    func delay(seconds : Float) -> Async {
        delay = seconds
        return self
    }
    
    func start() {
        if delay > 0 {
            if onBackgroundClosure != nil {
                dispatch_after(dispatch_time(DISPATCH_TIME_NOW, Int64(Double(self.delay) * Double(NSEC_PER_SEC))),
                    dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_LOW, 0),
                    {
                        self.onBackgroundClosure!()
                        if self.onMainThreadClosure != nil {
                            dispatch_async(dispatch_get_main_queue(), self.onMainThreadClosure!)
                        }
                })
            } else if onMainThreadClosure != nil {
                dispatch_after(dispatch_time(DISPATCH_TIME_NOW, Int64(Double(self.delay) * Double(NSEC_PER_SEC))),
                    dispatch_get_main_queue(), onMainThreadClosure!)
            }
        } else {
            if onBackgroundClosure != nil {
                dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_LOW, 0), {
                    self.onBackgroundClosure!()
                    if self.onMainThreadClosure != nil {
                        dispatch_async(dispatch_get_main_queue(), self.onMainThreadClosure!)
                    }
                })
            } else if onMainThreadClosure != nil {
                dispatch_async(dispatch_get_main_queue(), self.onMainThreadClosure!)
            }
        }
    }
    
}