draw function causes app to lag - iphone

Question

I'm using a draw function to highlight the score inserted into a table of highscores but i find that it makes my app lag when i try to leave the highscore layer. I'm still relatively new to cocos2d so I was wondering if there is a better way so it doesn't cause any lag. I find if i comment out this function that the isn't any lag. Heres my code:
- (void)draw {
[super draw];
if(currentScorePosition < 0 || currentScore==0) return;
float w = 320.0f;
float h = 20.0f;
float x = (320.0f - w) / 2.0f;
float y = 230.0f - currentScorePosition * h;
CGPoint vertices[4];
vertices[0] = ccp(x, y);
vertices[1] = ccp(x+w, y);
vertices[2] = ccp(x+w, y+h);
vertices[3] = ccp(x, y+h);
CCDrawNode *draw = [[[CCDrawNode alloc] init] autorelease];
[draw drawPolyWithVerts:vertices count:4 fillColor:ccc4f(0.5, 0.5, 0.8, 0.5) borderWidth:2.0 borderColor:ccc4f(0.0, 0.0, 0.0, 0.0)];
[self addChild:draw z:0 ];
}

Answer 1

You're creating a new CCDrawNode every frame. Over time this will slow down the game as it has to draw more and more draw nodes.
Solution: create one draw node up front and add it as child. Keep a reference to it in an ivar. Perform drawing with just this single draw node.
Note that the draw methods of CCDrawNode are still additive. If you want to draw just this one polygon and update it over time, then you'll have to call clear before drawing:
[theDrawNode clear];
[theDrawNode drawPolyWithVerts:vertices
count:4
fillColor:ccc4f(0.5, 0.5, 0.8, 0.5)
borderWidth:2.0
borderColor:ccc4f(0.0, 0.0, 0.0, 0.0)];
Another note: you can use the draw node outside the draw method. In fact if you run the code like you did, the draw node won't be drawn until the next frame and thus it'll always lag 1 frame behind. Use a scheduled update method to update the draw node.