Swift: Async callback block pattern example

ClassA.swift

//ClassA it's the owner of the callback, he will trigger the callback when it's the time
class ClassA {
    //The property of that will be associated to the ClassB callback
    var callbackBlock : ((error : NSError?, message : String?, adress : String? ) -> Void)?
    
    init() {
        //Do Your staff
    }
    
    //Define your function with the clousure as a parameter
    func yourFunctionWithCallback(#functionCallbackParameter : (error : NSError?,message : String?, adress : String?) -> ()) {
        //Set the calback with the calback in the function parameter
        self.callbackBlock = functionCallbackParameter
    }
    
    //Later On..
    func callbackTrigger() {
        self.callbackBlock?(error: nil,message: "Hello callback", adress: "I don't know")
        
    }
}

ClassB.swift

/ClassB it's the callback reciver the callback
class ClassB {
    @IBAction func testCallbackFunction(sender: UIButton) {
        let classA = ClassA()
        classA.yourFunctionWithCallback { (error, message, adress) -> () in
            //Do your stuff
        }
    }
}