I am making a button class and I would like it to take a void as an argument(in the constroctor) so that the void gets called when the user clicks it. So that I don't have to void mouseClicked() {if (button.mouseIsIn()) {doIt();} and it automatically gets called when the user clicks it. Like Button button = new Button(x,y,width,height,handleMouseClick());. Thanks in advance.
First of all, there's no such thing as "a void" - you can have a function with a void return type, but it doesn't make sense to call them voids.
That being said, this depends on whether you're using Java or JavaScript mode. Assuming you're using Java mode, then the answer is no, you can't pass functions as parameters. What you can do instead is pass an instance of a class, and then call the functions of that class. Something like this:
class MyAction{
void doIt(){
//whatever
}
}
Once you have this class defined, you can create an instance of it using the new keyword:
MyAction myAction = new MyAction();
Which you can then pass into your Button constructor:
Button button = new Button(x, y, width, height, myAction);
Then in your Button class, you can simply call myAction.doIt() whenever you want to call the function:
void mouseClicked() {
if (button.mouseIsIn()) {
myAction.doIt();
}
}
You can combine this approach with anonymous inner classes to allow you to create MyAction instances on the fly with their own implementation of doIt(). Something like this:
MyAction actionOne = new MyAction(){
void doIt(){
doThingOne();
}
}
Button buttonOne = new Button(1, 2, 3, 4, actionOne);
MyAction actionTwo = new MyAction(){
void doIt(){
doThingTwo();
}
}
Button buttonTwo = new Button(1, 2, 3, 4, actionTwo);
If you're using JavaScript mode, then you can just pass functions as arguments directly.
More info can be found by googling "Java pass function as parameter" or "JavaScript pass function as parameter".
Related
I have a WindowedApplication in Apache/Adobe Flex 4 which currently consists of one view (the view defined in the WindowedApplication MXML).
In that application I have an object which listens to data coming from a network. When data is available a method is called on that object and it shall update my view by changing the text of a label.
I do not have a reference to the view in the network listener object though. How can I get it?
This is part of my MXML where I define my view.
<fx:Script source="./ViewCodeBehind.as"/>
<!-- ommited stuff -->
<s:Label id="errorLabel"
text=""
fontSize="14"/>
<!-- Stuff in between -->
<s:Button label="Get Status"
click="getStatus();"/>
The code which is called when the button is clicked:
public function getStatus(): void
{
var networkGateway: NetworkGateway = new NetworkGatewayImpl();
networkGateway.getConnectionStatus();
}
And the NetworkGatewayImpl
public class NetworkGatewayImpl implements NetworkGateway
{
public function NetworkGatewayImpl()
{
}
public function getConnectionStatus(): void
{
// Start asynchronous network call
// when error occurs onNetworkError() is called
}
private function onNetworkError(): void
{
// Set "errorLabel" here: How?
}
}
Essentially I want to know some ways to update "errorLabel" from the NetworkGatewayImpl.
Based on your code, there could be multiple ways to solve this. Easiest way (as per me) would be to dispatch an event from the NetworkGatewayImpl class and listen to it on the instance you have created in the view class. So sample code would look like this:
public function getStatus(): void
{
var networkGateway: NetworkGateway = new NetworkGatewayImpl();
networkGateway.addEventListener("networkError", onNetworkError);
networkGateway.getConnectionStatus();
}
private function onNetworkError(e:Event):void
{
networkGateway.removeEventListener("networkError", onNetworkError);
this.errorLabel.text = "Your Text Here";
}
Dispatch your event like this from your NetworkGatewayImpl class:
private function onNetworkError(): void
{
this.dispatchEvent("networkError");
}
You will have to ensure that your NetworkGatewayImpl also implements the IEventDispatcher interface to be able to dispatch events.
Also, best practice would be to create a custom Event class (extending the Event class) and use constants instead of the literal 'networkError'
Hope this helps.
I am new to Haxe and probably this is a pretty basic question, which I can't really find an answer.
I see three ways to call main class:
1) use main()
//Entry point
public static main():void{
//do something...
}
2) use constructor new()
//Constructor
public function new(){
// init
}
3) use both main() and new()
static function main()
{
Lib.window.onload = function(e) new Main();
}
public function new()
{
//init
}
Is there a guideline or best practice to which one to use?
Thanks
Addressing all 3:
static function main() {} is the correct entry point. No matter which target, Haxe always begins execution at main().
The new() constructor isn't called automatically, if you want your main app to execute as an object rather than from a static function, you have to explicitly create the object: static function main() { new Main(); }
Some people prefer to keep their code in an object, rather than in static functions, which is where your 3rd example comes from. I usually do, and that's what you show in your 3rd example.
A few extra points:
The steps things are executed is explained here, basic summary:
All types/classes are registered
Boot.__init() runs platform specific initializations
Classes which have static function __init__() initialization methods are initialized
Static variables are intiailzed
Your main() function is executed
If you compile a class without a -main Main argument, but with the class path/name as an argument (eg haxe my.pack.MyClass) and with no public static function main(), the class is compiled, but it is not run automatically. This can be useful if you are creating a library or something similar - your class is there, but it needs to be called explicitly by some other Javascript etc.
In Javascript, the Haxe code starts running as soon as it is loaded, possibly before the DOM is ready. That is why it is a good idea to do:
static function main() {
js.Lib.window.onload = function(e) { runMyApp(); }
}
As you did in your example, this is a good idea if you want your code to run after the DOM is ready. Whether on load you call another static function, or instantiate a new MyApp() and run your app from there, that is up to you.
So I'm reading a book about MVC and the author create a controller (PlayerController) and put some functions for keyboard use and some for mouse use. But he just comment out every keyboard use.
It gave me a idea to create 2 controllers, PlayerMouseController and PlayerKeyboardController so I can decide how to control the player changing one line. And if I can design this way, later I can add a AIController for monsters that use the same view and model but are controlled by AI and so on...
I have my model Player and it do the physics stuff. Now I want two controller, one for mouse and other for keyboard. So I create a PlayerMouseController and PlayerKeyboardController.
The PlayerMouseController has 2 functions: processUpdate() and processMouseDown()
The PlayerKeyboardController has 2 functions: processKeyDown() and processKeyUp()
I create the object like this:
_player = new Player();
_playerController = new PlayerMouseController(_player);
_playerView = new PlayerView(_player, _playerController, stage);
addChild(_playerView);
If I want to change the controller I can just change the _playerController line for this:
_playerController = new PlayerKeyboardController(_player);
And it works fine... But I dont know if the design I use is fine for a large project
To make this work I have to create a Controller class with nothing so I can extends the others controllers and my view can call all methods.
public class Controller
{
public function processKeyDown(e:KeyboardEvent):void
{
}
public function processKeyUp(e:KeyboardEvent):void
{
}
public function processUpdate(stage:Stage):void
{
}
public function processMouseDown(e:MouseEvent):void
{
}
}
In my view (PlayerView) I accept any Controller:
public function PlayerView(model:Player, controller:Controller, stage:Stage)
{
_model = model;
_controller = controller;
_stage = stage;
}
and I decide what to use based on its type:
if (_controller is PlayerKeyboardController)
{
_stage.addEventListener(KeyboardEvent.KEY_DOWN, onKeyDown);
_stage.addEventListener(KeyboardEvent.KEY_UP, onKeyUp);
}
else if (_controller is PlayerMouseController)
{
_model.addEventListener(Model.UPDATE, onUpdate);
_stage.addEventListener(MouseEvent.MOUSE_DOWN, onMouseDown);
}
// EVENTS PlayerKeyboardController
private function onKeyDown(e:KeyboardEvent):void
{
_controller.processKeyDown(e);
}
private function onKeyUp(e:KeyboardEvent):void
{
_controller.processKeyUp(e);
}
// EVENTS PlayerMouseController
private function onUpdate(e:Event):void
{
_controller.processUpdate(_stage);
}
private function onMouseDown(e:MouseEvent):void
{
_controller.processMouseDown(e);
}
So... this is a good idea? How should I improve??
I think as your project evolves you'll soon hit a bottleneck with this kind of approach. I'd suggest creating a general IEntityController interface (don't be afraid of the word 'entity', it just shows that this is a game object controller, something that is parent for example of hero, enemy, etc.).
Then I'd create two separate implementations of this interface: BasicMouseController and BasicKeyboardController, so that I'd have two branches of these controllers with basic logic. If you need additional functionality for the Hero, you'd create a HeroMouseController class which would extend the BasicMouseController class and would have the advantage of calling super methods and adding the extended functionality easily.
You'd still have the benefit of passing different controllers to the PlayerView class as it's constructor would receive an IEntityController as a parameter, meaning anything implementing this class can be passed in.
There are many approaches for problems like this and StackOverflow is usually not meant to give these kind of answers, as every answer to these kind of questions is subjective and this website more fit for Problem/Solution kind of posts.
Hi guys,
I have two objects on stage so I presume they are in the Display list as well (Progress_mc, Ship_mc). I have Calculator class which doesn't represent any visual shape or anything but as3 code so it isn't in the display list.
What is the best way to work with the properties of Progress_mc?
Example: Calculator_as has to receive Progress_mc.width any time width has been changed and after some calculation Calculator has to send some calculated results to Ship_mc.x.
I was thinking if I have to addChild(Calculator) on stage so I can have access to those MCs in Calculator.as but this class isn't a visual object so I am not sure this is the right way.
Or I have to do this (code below) in Calculator class and then try to access the properties but I this way wont work either because the properties wont be of the instances on stage:
private var prg:Progress_mc = new Progress_mc;
private var ship:Ship_mc = new Ship_mc;
Or I have to add them as children of Calculator and add Calculator on stage?
The other problem is that I can't just use setter and getter as static functions in Calculator because "width" property is a read-only and cannot be used in static function (error:?)
What is the best way to access those properties and manipulate them?
Thank you so much good people!
I'm assuming Calculator instance is sort of globally accessible. In that case, I think you have
public function setProgressMcWidth(width:Number):void {...}
in Calculator class. This function needs to be called whenever progressMc's width is updated. Later when calculator needs to pass some width to shipMc, it can dispatch an event such as
package {
public class CalculatorEvent extends Event {
private var _width:Number = width;
public function CalculatorEvent(type:String, width:Number)
{
super(type);
_width = width;
}
override public function clone():Event {
var ret:CalculatorEvent = new CalculatorEvent(type, _width);
return ret;
}
public function getWidth():Number {return _width;}
}
}
and have dispatch code in Calculator like:
dispatch(new CalculatorEvent("shipWidthCalculated", calculatedShipWidth));
Ship mc, in turn, would listen to calculator's event like:
calculator.addEventListener("shipWidthCalculated", handleShipWidthCalculated);
private function handleShipWidthCalculated(event:CalculatorEvent):void {
trace('calculator calculated my width to be: ' + event.getWidth);
}
But if the calculator instance isn't in the display list, it won't receive any events.
Behold this example:
addEventListener("myEventType", myFunction("argument"));
function myFunction(args:String):Function {
return function(evt:Event):void {
trace(evt.currentTarget, "has", args);
};
}
dispatchEvent(new Event("myEventType", true));
It works.
Can I do something similar, but passing "argument" through dispatchEvent()?
It'd be very handy in a situation where dispatchEvent() is in a wholly separated class from addEventListener() and myFunction().
I'll be needing this a lot, so I want to do it without creating a custom event class for every situation.
You can use native flash.events.DataEvent for passing String parameter or create custom DataEvent with data:* property in all situations where you need to pass parameters to event handler.
If you want to customize the behavior of event listener in the place of adding event listener you can create "listener" object for holding this custom parameters (but I think this technique is more complicated than custom events):
addEventListener("myEventType", new EventListener("param1").onEvent);, whereEventListener is the class like this:
public class EventListener
{
private var params:*;
public function EventListener(params:*)
{
this.params = params;
}
public function onEvent(event:Event):void
{
trace("onEvent, params = ", params);
}
}
You could take a look at Signals (https://github.com/robertpenner/as3-signals). They are an alternative to Events and you can send whatever extra params you want with a Signal.