Rusher 2 – Composite Commands

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Example source

The previous command tutorial covered the basics of simple command executions in Rusher 2. Here I’m going to show you how to make use of on of the two composite commands, the SerialCommand.

Basically, a serial command does what its name suggests: it executes its subcommands in series, one after another. This heavily depends on the Command.onComplete signal dispatched when the Command.complete() method is invoked. Whenever the command’s job is complete, remember to invoke the Command.complete() method; otherwise, things may not work out as you expect.

There is two way of adding subcommands to a serial command. First, pass in commands as constructor arguments in the order desired. Second, use the inherited CompositeCommand.append() method to dynamically add subcommands in the order you’d like.

The example in this tutorial is going to be based on the previous command example. We’re only going to alter the EntityCreator system.

First, we’ll need to mark the systems we need for dependency injection.

public var entityManager:IEntityManager;

public var mouse:Mouse;

public var commandManager:CommandManager;

public var clock:Clock;

We’ll need a new array property to hold the Position components of the 5 circles we’re going to control with commands.

private var _circlePositions:Array;

And below is the new onAdd() method. Here we create 5 entities with a View component and a Position component. At the end we listen to the clock signal.

public function onAdd():void
    _circlePositions = [];
    //create 5 circles
    for (var i:int = 0; i < 5; ++i)
        var c:IEntity = entityManager.createEntity();
        var p:Position = new Position(400, 300);
        c.addComponent(new View(new CircleGraphics()));
        //push position components to array

In the clock listener, we constantly inspect the Mouse.isPressed() query. Note this is different from the Mouse.isDown() method, which returns true as long as the mouse button is held down. The Mouse.isPressed() will only return true for one frame, and then it returns false until the next time the mouse button is released and pressed again. This is useful for actions depending on “one shot” mouse clicks.

private function update(dt:Number):void
    if (mouse.isPressed())
        var moveCircles:SerialCommand = new SerialCommand();
        for (var i:int = 0; i < 5; ++i)
            //append tween command to serial command
                new TweenNanoTo
                        x: mouse.x, 
                        y: mouse.y, 
                        delay: 0.025 * i, 
                        overwrite: true
        //execute the serial command

And we’re done! You can run the example and see how each circle starts moving after the previous circle is finished moving. These commands are chained together by the serial command.

The ParallelCommand class is pretty much the same, only that all subcommands are executed simultaneously, and the parallel command fires a complete signal only when all the subcommands are complete.

Next up, state machines.

About Allen Chou

Physics / Graphics / Procedural Animation / Visuals
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