Run method only after other - objective-c

Question

i need to make this methods:
1) find and remove matches
2) fill empty cells
3) do 1 and 2 while no matches found
4) only when no matches found - find reshuffle method
How i do this :
[self launchAsyncCheckAndFill:^{
[self isReshuffleNeeded];
}];
-(void)launchAsyncCheckAndFill:(void(^)(void))completionHandler {
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
[self performSelectorOnMainThread:#selector(check) withObject:nil waitUntilDone:true];
dispatch_async(dispatch_get_main_queue(), ^{
completionHandler();
});
});
}
- (void) check {
[self performSelector:#selector(fillEmptyCells) withObject:nil afterDelay:0.4];
dispatch_after(dispatch_time(DISPATCH_TIME_NOW, 0.5 * NSEC_PER_SEC), dispatch_get_current_queue(), ^{
if ([self checkMapForMatchesWithFindMatchesMode:NO isCopyVector:NO]) {
[self check];
}
});
}
First of all i'm remove matches, then i go this methods : first of all i go launchAsyncCheckAndFill method, that on call back must start reshuffle method.
launchAsyncCheckAndFill must send callback only when check method is done. Check method is done in loop, this method must always fillEmptyCells, then checkmatches and while matches not found, only then must work callback on launchAsyncCheckAndFill .
But now behavior, that in loop always removing match, but method on reshuffle works after first remove and fill.
btw time 0.4 , 0.5 it's for animation, for this time figures moves and changes position. unfortunately in cocos i can only use
[elem.sprite runAction:[CCMoveTo actionWithDuration:0.4f position:elemPos1]];
that put position only after delay.
UPDATE:
[self launchAsyncCheckAndFills];
[self isReshuffleNeeded];
-(void)launchAsyncCheckAndFills {
dispatch_group_t group = dispatch_group_create();
dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);
dispatch_group_async(group, queue, ^{
[self check];
});
dispatch_group_wait(group, DISPATCH_TIME_FOREVER);
dispatch_release(group);
}
- (void) check {
[self performSelector:#selector(fillEmptyCells) withObject:nil afterDelay:0.4];
dispatch_after(dispatch_time(DISPATCH_TIME_NOW, 0.5 * NSEC_PER_SEC), dispatch_get_current_queue(), ^{
if ([self checkMapForMatchesWithFindMatchesMode:NO isCopyVector:NO]) {
[self check];
}
});
}