cocos-2d: Randomly Falling Blocks - iphone

Question

so I want to randomly create falling blocks. The blocks can be GRects or Sprites, I just have no clue how to go about it.
I need to both randomly choose a time to call the createBlock function. Then I need it to create a block at the top of the screen that falls to the bottom off the screen. The end result should be an endless flow of blocks falling off the screen. I'm less concerned with the random interval part and more concerned with getting as many blocks as I need to fall.
Thanks in advance!

Answer 1

Well, assuming you have a basic understanding of how cocos2d operates (layers, scenes, children, etc), this is how you might go about it.
CGSize winSize = [[CCDirector shareDirector] winSize];
CCSprite *block = [CCSprite spriteWithFile:#"block.png"];
// Generate a random x position
CGFloat x = arc4random() % winSize.width;
// Position the block at a random x, just above the top of the screen
block.position = ccp(x, winSize.height + block.contentSize.height/2);
// Tell the block to fall down to the bottom of the screen over 2 seconds
CCMoveTo *fall = [CCMoveTo actionWithDuration:2 position:ccp(block.position.x, 0 - block.contentSize.height/2)];
[block runAction:fall];
If you wanted this to occur in a constant stream of blocks, you can setup a callback function to call your "createBlock" function every so often. It's not very efficient to constantly recreate blocks, but it's more simple than maintaining a list of off-screen blocks and moving them up to the top to fall again when necessary.
CCSequence *rainBlocks = [CCSequence actions: [CCCallBlock actionWithBlock:^{
[self createBlock];
}],
[CCDelayTime actionWithDuration:3],
nil]];
[self runAction:[CCRepeatForever actionWithAction:rainBlocks]];
I'm not 100% on the syntax there, but that's the general idea.