day-070

Day 70: Project 20: Fireworks Night, Part One

This day covers the first part of Project 20: Fireworks Night in Hacking with Swift. You can follow along directly here.

📒 Field Notes

I previously created projects alongside Hacking with Swift in a separate repository. For 100 Days of Swift, however, I've been extending things further and adding my revised projects to this repo under each "Part One" folder.

With that in mind, Day 70 focuses on several specific topics:

• Ready... aim... fire: Timer and SKAction.follow()
• Swipe to select

Timer and SKAction.follow()

Similar to the way we might spawn enemies in a game, we can also configure a timer to "spawn" rockets — calling a function that generates a random launch configuration on each loop.

func setupTimer() {
    gameTimer = Timer.scheduledTimer(
        timeInterval: fireworkInterval,
        target: self,
        selector: #selector(launchFireworks),
        userInfo: nil,
        repeats: true
    )
}

Nifty 🚀.

One thing I found challenging was devising a clean structure for these random configurations. It shouldn't be necessary to write out massive lists of hand-picked starting points and x-and-y-movements.

So I decided to organize each launch style as an enum, switch on a random case, then call a specialized method for each launch style:

@objc func launchFireworks() {
    let burstQuantity = 5
    let spacingIncrement = CGFloat(frame.maxY / CGFloat(burstQuantity)) / 2

    switch LaunchStyle.allCases.randomElement()! {
    case .straightUp:
        launchStraightUp(numFireworks: burstQuantity, spacingIncrement: spacingIncrement)
    case .fanUp:
        launchFanUp(numFireworks: burstQuantity, spacingIncrement: spacingIncrement)
    case .leftToRight:
        launchLeftToRight(numFireworks: burstQuantity, spacingIncrement: spacingIncrement)
    case .rightToLeft:
        launchRightToLeft(numFireworks: burstQuantity, spacingIncrement: spacingIncrement)
    }
}

func launchLeftToRight(numFireworks: Int, spacingIncrement: CGFloat) {
    let startY = frame.midY - CGFloat(spacingIncrement * floor(CGFloat(numFireworks) / 2))

    for n in 0 ..< numFireworks {
        let yPosition = startY + (CGFloat(n) * spacingIncrement)
        let xMovement = frame.maxX * 1.5

        createLaunch(xMovement: xMovement, xPos: frame.minX - launchEdgeOffset, yPos: yPosition)
    }
}

The createLaunch method is its own awesomeness as it attaches a motion action to the firework node that lets it move along a UIBezierPath. I can instantly see about a million different use cases for this, but for now, it gets our rockets launching onwards and upwards 🚀🚀🚀.

Swipe to select

Our goal is to have the user touch all rockets of a single color and then shake the device to detonate them. This means that in both touchesBegan (for individual presses) and touchesMoved (for swiping), we need to be calling some kind of method that can track all touched rockets of a single color. We'll also be turning them white to indicate a selected rocket to the user.

override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {
    super.touchesBegan(touches, with: event)

    guard let touch = touches.first else { return }
    handleTouch(touch)
}

func handleTouch(_ touch: UITouch) {
    let nodesAtTouchPoint = nodes(at: touch.location(in: self))

    for case let touchedNode as SKSpriteNode in nodesAtTouchPoint {
        guard touchedNode.name == NodeName.fireworkRocket else { continue }

        if !selectedRockets.isEmpty && touchedNode.color != colorToDetonate {
            resetSelectedRockets()
        } else {
            colorToDetonate = touchedNode.color
            touchedNode.name = NodeName.selectedFireworkRocket
            touchedNode.colorBlendFactor = 0
            touchedNode.color = UIColor.white
            selectedRockets.append(touchedNode)
        }
    }
}

This is where the beauty of for case let really makes itself apparent. In a single statement, we can setup a loop that matches on SKSpriteNodes only, and initialize a touchedNode value for us to use inside of the loop. From there, all we need to do is check its name to see if it's a firework node, and if so, we can dig a bit deeper into our selection logic.