Cocos2D Tutorial for iOS: How To Create A Mole Whacking Game: Part 1/2

Popping the Moles

Now that we’re sure the moles are in the right place, let’s add the code to make them pop out of their holes.

First things first – switch the z-value of 999 for the mole sprite sheet back to 0 so the moles are underground.

Once that’s done, add the following line of code to the bottom of your init method:

[self schedule:@selector(tryPopMoles:) interval:0.5];

If you haven’t seen this before, you can run the schedule method on a node to tell Cocos2D to call another method every so many seconds. In this case, we want to try popping some moles out of their holes every 1/2 second.

Next, add the implementation of tryPopMoles:

- (void)tryPopMoles:(ccTime)dt {
    for (CCSprite *mole in moles) {            
        if (arc4random() % 3 == 0) {
            if (mole.numberOfRunningActions == 0) {
                [self popMole:mole];
            }
        }
    }     
}

This method will be called every 1/2 second, and each time it will loop through each mole and give it a 1 in 3 chance of popping out of its hole. But it will only pop out if it isn’t moving already – and one easy way to check for this is to see if the numbef running actions is 0.

Finally, add the implementation of popMole:

- (void) popMole:(CCSprite *)mole {          
    CCMoveBy *moveUp = [CCMoveBy actionWithDuration:0.2 position:ccp(0, mole.contentSize.height)]; // 1
    CCEaseInOut *easeMoveUp = [CCEaseInOut actionWithAction:moveUp rate:3.0]; // 2
    CCAction *easeMoveDown = [easeMoveUp reverse]; // 3
    CCDelayTime *delay = [CCDelayTime actionWithDuration:0.5]; // 4
    
    [mole runAction:[CCSequence actions:easeMoveUp, delay, easeMoveDown, nil]]; // 5
}

This code uses some Cocos2D actions to make the mole pop out of it’s hole, pause for half a second, then pop back down. Let’s go through this line by line to make sure we’re on the same page:

1. Creates an action to move the mole move up along the Y axis as much as the mole is tall. Since we placed the mole right below the hole, it will look right.
2. To make the movement look more natural, it wraps the move action with a CCEaseInOut action. This causes the action to go slower at the beginning and end, as if the mole is accelerating/decellerating, as it naturally would.
3. To create an action to move the mole move back down again, an easy way is to call the reverse method on an action, which will give its opposite.
4. Creates an action to pause for one second after the mole pops out.
5. Now that the actions are ready to go, it runs them on the mole in a sequence: move up, delay, and finally move down. Note it has to terminate the sequence with a nil to show it’s done.

That’s it! Compile and run the code, and you’ll see the moles happily popping out of their holes!

Where To Go From Here?

Here is a sample project with all of the code we’ve developed so far in this Cocos2D tutorial series.

Next check out Part 2, where we’ll add some cute animations to the mole as he laughs and gets whacked, add gameplay so you can do the whacking and earn points, and of course add some gratuitous sound effects as usual.

Please add a comment below in if you have any thoughts, advice, or suggestions for future tutorials!