Using Swift Playgrounds for UI

We can use Playgrounds to experiment with UI and test custom views and interfaces. In this recipe, we will build a bar chart view that we can use to display numerical data in chart form and use a playground to test it.

Getting ready

First, we'll create an iOS-based playground to build our bar chart. In Chapter 1, Swift Building Blocks, we went through creating a new playground, so return there if you need a refresher.

We will create a custom view that will display information in bar chart form, and use that to test some features of playgrounds. You can either enter the following code into a new iOS-based playground or download the playground named Simple_iOS.playground from this book's GitHub repository:

1. Create a Color struct:

import UIKit

struct Color {
    let red: Float
    let green: Float
    let blue: Float
    let alpha: Float = 1.0
    
    var displayColor: UIColor {
        return UIColor(red: CGFloat(red),
                       green: CGFloat...