Custom progress bar with text

custom-progress-bar-with-text.swift

//
//  PlainHorizontalProgressBar.swift
//
//  Created by Julia Nikitina on 23.05.2020.
//  Copyright © 2020 Julia Nikitina. All rights reserved.
//

import UIKit
@IBDesignable
final class PlainHorizontalProgressBar: UIView {
    
    @IBInspectable
    private var color: UIColor? = .systemPurple
    
    var progress: CGFloat = 0.0 {
        didSet {
            setNeedsDisplay()
        }
    }
    
    private let progressLayer = CALayer()
    
    private let yellowTextLayer = CATextLayer()
    private let purpleTextLayer = CATextLayer()
    
    private let yellowMaskLayer = CAShapeLayer()
    private let purpleMaskLayer = CAShapeLayer()
    
    override init(frame: CGRect) {
        super.init(frame: frame)
        setupTextLayers()
        setupProgressLayer()
    }
    
    required init?(coder: NSCoder) {
        super.init(coder: coder)
        setupTextLayers()
        setupProgressLayer()
    }

    override func draw(_ rect: CGRect) {
        let progressRect = CGRect(
            origin: .zero,
            size: CGSize(width: bounds.width * progress, height: bounds.height)
        )
        
        let leftProgressRect = CGRect(
            origin: CGPoint(x: bounds.width * progress, y: 0),
            size: CGSize(width: bounds.width - bounds.width * progress, height: bounds.height)
        )
        
        let yellowMask = createMaskLayer(layer: yellowMaskLayer, leftProgressRect)
        let purpleMask = createMaskLayer(layer: purpleMaskLayer, progressRect)
        
        yellowTextLayer.mask = yellowMask
        purpleTextLayer.mask = purpleMask
                   
        progressLayer.frame = progressRect
    }
    
    private func setupProgressLayer() {
        layer.addSublayer(progressLayer)
        progressLayer.backgroundColor = color?.cgColor
        
        let backgroundMask = CAShapeLayer()
        backgroundMask.path = UIBezierPath(roundedRect: bounds, cornerRadius: bounds.height * 0.25).cgPath
        layer.mask = backgroundMask
    }
    
    private func setupTextLayers() {
        [yellowTextLayer, purpleTextLayer].forEach {
            $0.string = "Optimization..."
            $0.fontSize = 17
            $0.contentsScale = UIScreen.main.scale
            $0.alignmentMode = .center
            $0.frame = bounds
            layer.addSublayer($0)
        }
    
        yellowTextLayer.foregroundColor = UIColor.systemYellow.cgColor
        purpleTextLayer.foregroundColor = UIColor.systemPurple.cgColor
    }
    
    private func createMaskLayer(layer: CAShapeLayer, _ holeRect: CGRect) -> CAShapeLayer {
        
        let path = CGMutablePath()

        path.addRect(holeRect)
        path.addRect(bounds)

        layer.path = path
        layer.fillRule = .evenOdd
        layer.opacity = 1

        return layer
    }
}