How frames work on macOS - Example 1

Example1.swift

import Cocoa

class ContainerView: ColorView {}
class ColorView: NSView {
  required init(frame: CGRect, color: NSColor) {
    super.init(frame: frame)
    wantsLayer = true
    layer?.backgroundColor = color.cgColor
  }

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

let containerFrame = CGRect(origin: .zero,
                            size: CGSize(width: 200, height: 200))
let containerView = ContainerView(frame: containerFrame,
                                  color: NSColor.blue.withAlphaComponent(0.25))

let colorFrame = CGRect(origin: .zero,
                        size: CGSize(width: 50, height: 50))
let colorView = ColorView(frame: colorFrame,
                          color: NSColor.green.withAlphaComponent(0.5))

containerView.addSubview(colorView)