A fast, easy to use, free, and community supported 2D game engine
I was just wondering why this doesn't work
_sprite.position.x += 5;
But this does
CGPoint pt = _sprite.position;
pt += 5;
_sprite.position = pt;
is it because the setPosition is overloaded and needs this line?
isTransformDirty_ = isInverseDirty_ = YES;
And is there a good way around it. Sometimes it would be a lot easier to increment an x or y rather than ccp() a new point.
Brayden
Member
It's because Cocos2D doesn't allow you to alter just the X or Y value individually, but you have to do it combined as a point. So for example, sprite.position.x is only one value of the point and you can't. But you should do it more like this:
sprite.position = ccp(sprite.position.x + 5 *dt, sprite.position.y);
Or something similar.
@michaelm -- Fundamentally, yes, the setter is overloaded and those _dirty methods need to be called.
Unless cocos changes from using CGPoints to using a different class to store points, I don't see this changing.
What I'd suggest is using a macro, something like "updateCCNodePositionX(node, amount)" that doe "node.position = ccp(node.position.x + amount, node.position.y)"
Tried it, didn't blow up but also didn't work. Something else is happening, may be the assign in the property for position creates a new cgpoint. Oh well not worth it to pursue, would just have been handy. Though there might be some benefit moving to an internal ccPoint and ccRect class, could write replacements for cgrectintersects etc. But that would be a lot of rewrite internally and a lot of breaking changes.
@easydev -- that is a good example and that will work, but it has two downsides:
1) Creating an action is somewhat expensive, cpu-wise; certainly compared to creating a new CGPoint struct.
2) Running multiple actions requires using CCSpawn or CCSequence, so you'd have to take other actions into account.
So, unless you have to move your object to a new position over time, I'd go with just setting the position directly with:
sprite.position = ccp(sprite.position.x + newValue, sprite.position.y);
It's significantly faster and also would be cumulative with any other actions you are taking on the object.
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