CS193p class note - 6 Multitouch

Memo:

. set contentMode to 'redraw' will call the drawRect in custom view
. call setNeedsDisplay and drawRect will be called
. call setNeedLayout if you want to layout the subviews
. label.frame.size = CGSize.zero before calling label.sizeToFit() if you want the system to adjust the size for you. If there is width for the label, calling sizeToFit only adjusts the height.
. CGAffineTransform has three methods: scale, translate and rotate
. traitCollectionDidChange is called when dynamic type is changed
. add @IBDesignable and storyboard will show the design
. add @IBInspectable and you can change the property in the storyboard
. UIGestureRecognizer has a variable state

override func draw(_ rect: CGRect) {
// create rounded corners
    let roundedRect = UIBezierPath(roundedRect: bounds, cornerRadius: 16.0)
    roundedRect.addClip()
    UIColor.white.setFill()
    roundedRect.fill()
}

private func centeredAttributedString(_ string: String, fontSize: CGFloat) -> NSAttributedString {
// create attributedString
    var font = UIFont.preferredFont(forTextStyle: .body).withSize(fontSize)
    font = UIFontMetrics(forTextStyle: .body).scaledFont(for: font)
    let paragraphStyle = NSMutableParagraphStyle()
    paragraphStyle.alignment = .center
    return NSAttributedString(string: string,
                              attributes: [.paragraphStyle: paragraphStyle,
                                           .font: font])
}

// how to deal with const in Swift
extension PlayingCardView {
    private struct SizeRatio {
        static let cornerFontSizeToBoundsHeight: CGFloat = 0.005
        static let cornerRadiusToBoundsHeight: CGFloat = 0.06
        static let cornerOffsetToCornerRadius: CGFloat = 0.33
        static let faceCardImageSizeToBoundsSize: CGFloat = 0.75
    }
}

// adding a gesture recognizer to a UIView
@IBOutlet weak var pannableView: UIView {
    didSet {
        let panGestureRecognizer = UIPanGestureRecognizer {
            target: self, action: #selector(someFunction)
        }
        pannableView.addGestureRecognizer(panGestureRecognizer)
    }
}