lifecycle

[churabou]

(1 )

        blue.backgroundColor = .blue
        view.addSubview(blue)

        blue.snp.makeConstraints { (make) in
            make.center.equalToSuperview()
            make.size.equalTo(100)
        }

        blue.backgroundColor = .blue
        view.addSubview(blue)

        blue.frame = view.frame

        blue.snp.makeConstraints { (make) in
            make.center.equalToSuperview()
            make.size.equalTo(100)
        }

        blue.frame = view.frame

    override func viewWillLayoutSubviews() {
        blue.frame = view.frame
    }

    override func viewDidLayoutSubviews() {
        blue.frame = view.frame
    }

---

class ViewController: UIViewController {

    private var blue = BlueView()

    override func viewDidLoad() {
        super.viewDidLoad()

        blue.backgroundColor = .blue
        view.addSubview(blue)
    }
}

class BlueView: UIView {

    override func layoutSubviews() {
        snp.makeConstraints { (make) in
            make.center.equalToSuperview()
            make.size.equalTo(100)
        }
    }
}

why

---

class ViewController: UIViewController {

    private var blue = BlueView()
    private var red = RedView()

    override func viewDidLoad() {
        super.viewDidLoad()

        blue.backgroundColor = .blue
        red.backgroundColor = .red
        view.addSubview(blue)
        blue.addSubview(red)
    }
}

class BlueView: UIView {

    override func draw(_ rect: CGRect) {
        print("blue draw")
    }

    override func layoutSubviews() {
        print("blue layoutSubviews")
        snp.makeConstraints { (make) in
            make.center.equalToSuperview()
            make.size.equalTo(100)
        }
    }
}

class RedView: UIView {

    override func draw(_ rect: CGRect) {
        print("red draw")
    }

    override func layoutSubviews() {
        print("red layoutSubviews")
        snp.makeConstraints { (make) in
            make.right.equalToSuperview()
            make.centerY.equalToSuperview()
            make.size.equalTo(50)
        }
    }
}

blue layoutSubviews
blue layoutSubviews
red layoutSubviews
blue layoutSubviews
red layoutSubviews
blue layoutSubviews
red layoutSubviews
blue draw
red draw

[churabou]

class BaseView: UIView {

    override init(frame: CGRect) {
        super.init(frame: frame)
        initializeView()
    }

    required init?(coder aDecoder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }

    func initializeView() {}
}

extension BaseView {

    func enableAutoLayout() {
        translatesAutoresizingMaskIntoConstraints = false
    }
}

[churabou]

class ViewController: UIViewController {

    private var blue = BlueView()

    override func viewDidLoad() {
        super.viewDidLoad()
        view.addSubview(blue)
    }
}

class BlueView: BaseView {

    private var orange = OrangeView()
    private var red = RedView()

    override func initializeView() {
        backgroundColor = .blue
        addSubview(orange)
        orange.addSubview(red)
    }

    override func _layoutSubviews() {

        snp.makeConstraints { (make) in
            make.center.equalToSuperview()
            make.size.equalTo(100)
        }

        orange.snp.makeConstraints { (make) in
            make.top.left.equalToSuperview()
            make.size.equalTo(40)
        }
    }
}

class RedView: BaseView {

    override func initializeView() {
        backgroundColor = .red
    }

    override func _layoutSubviews() {

        snp.makeConstraints { (make) in
            make.right.equalToSuperview()
            make.centerY.equalToSuperview()
            make.size.equalTo(20)
        }
    }
}

class OrangeView: BaseView {

    override func initializeView() {
        backgroundColor = .orange
    }
}

class BaseView: UIView {

    override init(frame: CGRect) {
        super.init(frame: frame)
        initializeView()
    }

    required init?(coder aDecoder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }

    func initializeView() {}

    override func layoutSubviews() {
        super.layoutSubviews()
        print("layoutSubviews: \(String(describing: type(of: self)) )")
        _layoutSubviews()
    }

    func _layoutSubviews() { }

    override func draw(_ rect: CGRect) {
        print("draw:  \(String(describing: type(of: self)) )")
    }
}

extension BaseView {

    func enableAutoLayout() {
        translatesAutoresizingMaskIntoConstraints = false
    }
}

layoutSubviews: BlueView
layoutSubviews: OrangeView
layoutSubviews: BlueView
layoutSubviews: OrangeView
layoutSubviews: RedView
layoutSubviews: OrangeView
layoutSubviews: RedView
layoutSubviews: RedView
draw:  BlueView
draw:  OrangeView
draw:  RedView

[churabou]

LayoutSubViewsは複数回呼ばれる。

class BlueView: BaseView {

    override func initializeView() {
        backgroundColor = .blue
    }

    override func layoutSubviews() {

        print("layout subviews")
        print("before \(frame)")
        snp.makeConstraints { (make) in
            make.size.equalTo(60)
            make.right.equalToSuperview()
            make.centerY.equalToSuperview()
        }
        print("after \(frame)")
    }
}

frameを決定する

[churabou]

制約の更新はupdateLayoutで行うのが良いらしい。

updateLayout -> layoutsubviews -> draw

子Viewから制約をつけていき、親Viewからレンダリングしていくらしい。

[churabou]

制約の更新を呼び出すには

    setNeedsUpdateConstraints()

updateConstraintsIfNeeded()
     layoutIfNeeded