Dynamically allocate a parameter for action when running a sequence

Question

I stumbled upon a problem and I can't find the answer for it. I am working with the SK template from Xcode to create an iOS game. I am a beginner, so bear with me.

Basically I have this code:

SKAction *releaseBubbles = [SKAction sequence:@[
                                                    [SKAction performSelector:@selector(createBubbleNode)onTarget:self],
                                                    [SKAction waitForDuration:speed]]];
[self runAction: [SKAction repeatAction:releaseBubbles
                                      count:300]];

which executes in

-(id)initWithSize:(CGSize)size {
    if (self = [super initWithSize:size]) {

I change the level to my game in -(void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event { and when I change the level it should also change that speed parameter. Of course, this doesn't work because I believe that my action is starting when the scene is initialised and I never get to switch the parameter.

What I need to do is populate the screen continuously with bubbles appearing at a certain pace (relative to the level).

I really have no clue how to fix this, because it seems to me like I need to stop and restart the action sequence somehow...

Looking forward to your valuable input.

Answer 1

To continuously populate the screen with bubbles you can use the update: method of your SKScene. Here is how to do it.

First, add a property that will store a date when you last added a bubble.

@property(nonatomic, strong) NSDate *lastBubbleCreationDate;

Then, change your update: method to:

-(void)update:(CFTimeInterval)currentTime
{
    // Create new bubble every 5s.
    if (ABS([_lastBubbleCreationDate timeIntervalSinceNow]) > 5)
    {
        [self createBubbleNode];
    }
}

Finally, in your createBubbleNode method you have to store the time when you created last bubble:

-(void)createBubbleNode
{
    // Your code here

    // Set the date to now.
    _lastBubbleCreationDate = [NSDate date];
}

You also need to call createBubbleNode to set the initial value of the _lastBubbleCreationDate. You can do this in didMoveToView: method. Just add this method to your scene implementation:

- (void)didMoveToView:(SKView *)view
{    
    // Creates first bubble and sets the initial value of the _lastBubbleCreationDate
    [self createBubbleNode];
}

In next levels you can just change the 5s value to create bubbles more often which will make the game more difficult.