Nape Moving Platform

Question

Okay Im relatively new to nape and Im in the process of making a game, I've made a Body called platform of type KINEMATIC, and I simply want to move it back a forth in a certain range on the stage. Can somebody please see where im going wrong , thanks.

private function enterFrameHandler(ev:Event):void
{
if (movingPlatform.position.x <= 150 )
            {
                movingPlatform.position.x +=  10;
            }
            if (movingPlatform.position.x >= 260)
            {
                movingPlatform.velocity.x -=  10;
            }
}

Answer 1

First of in one of the if blocks you are incrementing position.x by 10 in the other one you are decrementing velocity.x by 10. I guess you meant position.x in both.

Secondly, imagine movingPlatform.position.x is 150 and your enterFrameHandler runs once. movingPlatform.position.x will become 160 and on the next time enterFrameHandler is called none of the if blocks will execute since 160 is neither less than or equal to 150 or greater than or equal to 260.

You can use the velocity to indicate the side its moving and invert it once you go beyond an edge, something like :

// assuming velocity is (1,0)
private function enterFrameHandler(ev:Event):void {
    if (movingPlatform.position.x <= 150 || movingPlatform.position.x >= 260) {
        movingPlatform.velocity.x = -movingPlatform.velocity.x;
    }

    movingPlatform.position.x += movingPlatform.velocity.x;
}

Obviously this might cause problems if the object is already at let's say x=100, it will just keep inverting it's velocity, so either make sure you place it between 150-260 or add additional checks to prevent it from inverting it's direction more than once.

This might be a better way of doing it :

// assuming velocity is (1,0)
private function enterFrameHandler(ev:Event):void {
    if (movingPlatform.position.x <= 150) {
        movingPlatform.velocity.x = 1;
    } else if (movingPlatform.position.x >= 260) {
        movingPlatform.velocity.x = -1;
    }

    movingPlatform.position.x += movingPlatform.velocity.x;
}