We need to modify touchesMoved()
to detect when users slice penguins and bombs. The code isn't complicated, but it is long, so I'm going to split it into three. First, here's the structure – place this just before the end of touchesMoved()
:
let nodesAtPoint = nodes(at: location)
for case let node as SKSpriteNode in nodesAtPoint {
if node.name == "enemy" {
// destroy penguin
} else if node.name == "bomb" {
// destroy bomb
}
}
Now, let's take a look at what destroying a penguin should do. It should:
isDynamic
of its physics body so that it doesn't carry on falling.activeEnemies
array.Replace the // destroy penguin
with this, following along with my numbered comments:
// 1
if let emitter = SKEmitterNode(fileNamed: "sliceHitEnemy") {
emitter.position = node.position
addChild(emitter)
}
// 2
node.name = ""
// 3
node.physicsBody?.isDynamic = false
// 4
let scaleOut = SKAction.scale(to: 0.001, duration:0.2)
let fadeOut = SKAction.fadeOut(withDuration: 0.2)
let group = SKAction.group([scaleOut, fadeOut])
// 5
let seq = SKAction.sequence([group, .removeFromParent()])
node.run(seq)
// 6
score += 1
// 7
if let index = activeEnemies.firstIndex(of: node) {
activeEnemies.remove(at: index)
}
// 8
run(SKAction.playSoundFileNamed("whack.caf", waitForCompletion: false))
You've now seen the two ways of collecting SpriteKit actions together: groups and sequences. An action group specifies that all actions inside it should execute simultaneously, whereas an action sequence
runs them all one at a time. In the code above we have a group inside a sequence, which is common.
If the player swipes a bomb by accident, they lose the game immediately. This uses much the same code as destroying a penguin, but with a few differences:
activeEnemies
array..endGame()
.Replace the // destroy bomb
comment with this:
guard let bombContainer = node.parent as? SKSpriteNode else { continue }
if let emitter = SKEmitterNode(fileNamed: "sliceHitBomb") {
emitter.position = bombContainer.position
addChild(emitter)
}
node.name = ""
bombContainer.physicsBody?.isDynamic = false
let scaleOut = SKAction.scale(to: 0.001, duration:0.2)
let fadeOut = SKAction.fadeOut(withDuration: 0.2)
let group = SKAction.group([scaleOut, fadeOut])
let seq = SKAction.sequence([group, .removeFromParent()])
bombContainer.run(seq)
if let index = activeEnemies.firstIndex(of: bombContainer) {
activeEnemies.remove(at: index)
}
run(SKAction.playSoundFileNamed("explosion.caf", waitForCompletion: false))
endGame(triggeredByBomb: true)
Before I walk you through the endGame()
method, we need to adjust the update()
method a little. Right now, if a penguin or a bomb falls below -140, we remove it from the scene. We're going to modify that so that if the player misses slicing a penguin, they lose a life. We're also going to delete the node's name just in case any further checks for enemies or bombs happen – clearing the node name will avoid any problems.
In the update()
method, replace this code:
if node.position.y < -140 {
node.removeFromParent()
activeEnemies.remove(at: index)
}
…with this:
if node.position.y < -140 {
node.removeAllActions()
if node.name == "enemy" {
node.name = ""
subtractLife()
node.removeFromParent()
activeEnemies.remove(at: index)
} else if node.name == "bombContainer" {
node.name = ""
node.removeFromParent()
activeEnemies.remove(at: index)
}
}
That's mostly the same, except now we call subtractLife()
when the player lets any penguins through. So, if you miss a penguin you lose one life; if you swipe a bomb, you lose all your lives. Or at least you would if our code actually compiled, which it won't: you're missing the subtractLife()
and endGame()
methods!
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