pausing game run loop

I've created a small tutorial that will give you a pause button and you can then play around with it to your pleasing.

We have a property we can use in our SKScene called 'paused'

Paused - A Boolean value that determines whether to run actions, animations, particle systems, and physics simulations in the scene graph.

The problem with just toggling paused is that the update method and the touchesBegan method are still called whilst the scene is paused. This leads to problems like when you un-pause, a ton of space cats may spawn or you can tap the screen a whole bunch while paused to shoot a ton of fireballs at once.

Step 1: Create a property inside of our gameplay scene that will be our button.

@interface THGamePlayScene ()

@property (nonatomic) SKSpriteNode *pauseButton;

Step 2: Then initialize it in initWithSize.

-(id)initWithSize:(CGSize)size {
    if (self = [super initWithSize:size]) {
        ...
        _pauseButton = [SKSpriteNode spriteNodeWithColor:[UIColor redColor] size:CGSizeMake(50, 50)];
        _pauseButton.position = CGPointMake(self.frame.size.width-35, 35);
        [self addChild:_pauseButton];
        ...
    }
    return self;
}

Step 3: Now we check if the user taps our button in the touchesBegan method. I've also added a little touch up to the color of the sprite so that we can see if it is going to resume or pause. This effect looks really cool!

if ( CGRectContainsPoint(_pauseButton.frame, position) ) {
    self.scene.paused = !self.scene.paused;
    if (self.scene.paused == true) {
         _pauseButton.color = [UIColor greenColor];
    } else if (self.scene.paused == false) {
         _pauseButton.color = [UIColor redColor];
    }
}

Excellent! Now we just need to fix a few bugs, one being to stop the space cats from spawning while paused and the other to stop allowing shots while paused.

Step 4: To Stop the user from making a super shot, which is actually really fun to do, you need to add this to the touches began method. All we're doing is surrounding the shoot projectile method call so that they can't shoot while paused.

if ( self.scene.paused == false ) {
    [self shootProjectileTowardsPosition:position];
}

Step 5: Lastly, I surrounded the whole game content in the update method with an if statement so that the spawning only occurs whilst the game isn't paused.

- (void) update:(NSTimeInterval)currentTime {
    if (self.scene.paused == false) {
        //GAME UPDATE CONTENT
    }
}