I got this setup: update: function() { this.balls.forEach(this.ballUpdate, this);}ballUpdate: function(ball) {if (ball.body.y > this.game.world.height + ball.height) {ball.destroy();}}Which results in: Uncaught TypeError: Cannot read property 'alive' of null Game.js:566 BasicGame.Game.ballUpdateGame.js:566 Phaser.Group.forEachphaser.js:12324 BasicGame.Game.updateGame.js:173 Phaser.StateManager.updatephaser.js:10138 Phaser.Game.updatephaser.js:13701 Phaser.RequestAnimationFrame.updateRAFphaser.js:22114 _onLoopphaser.js:22099 I tried: update: function() { if(this.balls.countLiving() > 0) { this.balls.forEach(this.ballUpdate, this); }}