Moving a sprite accelerometer

Question

Im trying to, in cocos2d for the iPhone, move a CCSprite (in this case "player" up and down (the app is in landscape). How can I accomplish this? I have been unable to do so. ex.

-(void)accelerometer:(UIAccelerometer *)accelerometer didAccelerate:(UIAcceleration *)acceleration {
    player.position.x = acceleration.x * 10;
    NSLog(@"Accelerometer x value is %f\n", acceleration.x);
}

Answer 1

You can't change position components like x and y directly. You have to set a new position instead, by assigning a CGPoint to the position property. Something like this:

[player setPosition:ccp( acceleration.x * 10, player.position.y )];

If you want to move the sprite constantly in the direcion of acceleration, you should increment the x value instead.. something like this:

[player setPosition:
    ccp( player.position.x + acceleration.x * 10, player.position.y )];

Technical background: You have to use setPosition or position = ccp(xValue, yValue), because Cocos2D keeps a flag internally that indicates if the position has changed and if the sprite should be moved. Setting components like x or y directly won't do anything, because the flag only changes when you invoke the position setter.