Cocos2d 'snap to grid' logic - objective-c

Question

I'm building a game in Cocos2d and I'm having a hard time implementing what I want. Imagine an 8 x 10 grid of squares. You can touch a square and drag that square's row / column horizontally / vertically, but not both. After you release the row / column, the squares will 'snap' back into place in the grid according to their closest row / col positions.
Everything works programmatically, with no overlaps or misplaced squares or invalid positions. However, I just cannot seem to get this 'snap to grid' to animate the way I want.
I'm using the MVC design pattern to separate any views from any game logic. The view is simply handed an array of 'squaresToUpdate', looks at every square, finds the corresponding sprite, and updates the position of the sprite based on the position of the square.
The problem arises when trying to do something along the lines of this:
-update():
for each square in squaresToUpdate:
if square is not being dragged at the moment:
setup a 'CCMoveTo' to bring the sprite in line with square
I can't get the squares to move freely while being dragged, but CCMoveTo when not being dragged. Either I create a new action every update, or the squares just freak out.
I don't know if it's my logic that is broken, if CCMoveTo is not doing what I want, or if this problem is actually much harder than I initially thought. Could someone help me out with this logic?
Good old pencil and paper gives me this, but I'm not sure it's 100%:
- (void)update:(ccTime)dt {
NSMutableArray *toDraw = [self.rootView whatAmIDrawing];
for (GameObject *o in toDraw) {
CCSprite *sprite = (CCSprite*)[self.batch getChildByTag:o.tag];
if (o.moving == NO) {
if (o.snapping == NO) {
o.snapping = YES;
CCMoveTo *move = [CCMoveTo actionWithDuration:self.rootView.model.activeGame.snapSpeed position:o.position];
[sprite runAction:move];
}
} else {
o.snapping = NO;
sprite.position = o.position;
sprite.rotation = o.rotation;
}
}
[super update:dt];
}

Answer 1

I would override the cocos2d touch methods:
- (BOOL)ccTouchBegan:(UITouch *)touch withEvent:(UIEvent *)event
- (void)ccTouchMoved:(UITouch *)touch withEvent:(UIEvent *)event
- (void)ccTouchEnded:(UITouch *)touch withEvent:(UIEvent *)event
ccTouchBegan would compare the touch point with every game object and set a "touched" flag:
ccTouchMoved would set the position of any "touched" object to the new touch position, and set a "moving" flag.
ccTouchEnded would clear all "touched" flags, run the CCMoveTo to the new position for any object with the "moving" flag, and then clear all "moving" flags.
The update() method would then just have to change position of every sprite to the position of the object.