Swift Multi threading operator

Swift Multi threading operator

// Takes 2 closures. 
// Executes first closure in background and passes its value to the second closure on the ui thread

infix operator ~> {}

func ~> <T> (first:() -> T?, second:(result: T?) -> Void) -> Void {
    dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), { () -> Void in
        var result: T? = first()
        
        dispatch_async(dispatch_get_main_queue(), { () -> Void in
            second(result: result)
        })
    })
}

// Usage
{ return "Long running task" }  ~> { (result: String?) in self.label.text = result }