Custom view to show a simple pie chart

PieGraph.swift

//
//  PieGraph.swift
//
//  Created by Rigoberto Sáenz Imbacuán (https://www.linkedin.com/in/rsaenzi/)
//  Copyright © 2017. All rights reserved.
//

import UIKit

@IBDesignable
class PieGraph: UIView {

   private let pieColor = UIColor.red
   private let lineColor = UIColor.white
   private let sublineColor = UIColor.white.withAlphaComponent(0.5)

   private var pie5s: PieSlice!
   private var pie1m: PieSlice!
   private var pie5m: PieSlice!
   private var pie20m: PieSlice!

   private var line5sBest: PieArc!
   private var line5sVery: PieArc!
   private var line5sGood: PieArc!
   private var line5sNeeds: PieArc!

   private var line1mBest: PieArc!
   private var line1mVery: PieArc!
   private var line1mGood: PieArc!
   private var line1mNeeds: PieArc!

   private var line5mBest: PieArc!
   private var line5mVery: PieArc!
   private var line5mGood: PieArc!
   private var line5mNeeds: PieArc!

   override init(frame: CGRect) { // From Code
      super.init(frame: frame)
      commonInit()
   }

   required init?(coder aDecoder: NSCoder) { // From IB
      super.init(coder: aDecoder)
      commonInit()
   }

   private func commonInit() {
      pie5s = PieSlice(PieValues(start: 180, arc: 60, sliceRadius: 0.85, color: pieColor))
      pie1m = PieSlice(PieValues(start: 240, arc: 60, sliceRadius: 0.62, color: pieColor))
      pie5m = PieSlice(PieValues(start: 300, arc: 60, sliceRadius: 0.45, color: pieColor))
      pie20m = PieSlice(PieValues(start: 0, arc: 180, sliceRadius: 0.6, color: pieColor))

      line5sBest = PieArc(PieValues(start: 180, arc: 60, sliceRadius: 1.0, color: lineColor), lineWidth: 1)
      line5sVery = PieArc(PieValues(start: 180, arc: 60, sliceRadius: 0.75, color: sublineColor), lineWidth: 1)
      line5sGood = PieArc(PieValues(start: 180, arc: 60, sliceRadius: 0.5, color: sublineColor), lineWidth: 1)
      line5sNeeds = PieArc(PieValues(start: 180, arc: 60, sliceRadius: 0.25, color: sublineColor), lineWidth: 1)

      line1mBest = PieArc(PieValues(start: 240, arc: 60, sliceRadius: 1.0, color: lineColor), lineWidth: 1)
      line1mVery = PieArc(PieValues(start: 240, arc: 60, sliceRadius: 0.75, color: sublineColor), lineWidth: 1)
      line1mGood = PieArc(PieValues(start: 240, arc: 60, sliceRadius: 0.5, color: sublineColor), lineWidth: 1)
      line1mNeeds = PieArc(PieValues(start: 240, arc: 60, sliceRadius: 0.25, color: sublineColor), lineWidth: 1)

      line5mBest = PieArc(PieValues(start: 300, arc: 60, sliceRadius: 1.0, color: lineColor), lineWidth: 1)
      line5mVery = PieArc(PieValues(start: 300, arc: 60, sliceRadius: 0.75, color: sublineColor), lineWidth: 1)
      line5mGood = PieArc(PieValues(start: 300, arc: 60, sliceRadius: 0.5, color: sublineColor), lineWidth: 1)
      line5mNeeds = PieArc(PieValues(start: 300, arc: 60, sliceRadius: 0.25, color: sublineColor), lineWidth: 1)
   }

   // Only override draw() if you perform custom drawing.
   // An empty implementation adversely affects performance during animation.
   override func draw(_ rect: CGRect) {
      super.draw(rect)

      // Order of drawing is really important
      pie5s.draw(rect)
      pie1m.draw(rect)
      pie5m.draw(rect)
      pie20m.draw(rect)

      line5sBest.draw(rect)
      line5sVery.draw(rect)
      line5sGood.draw(rect)
      line5sNeeds.draw(rect)

      line1mBest.draw(rect)
      line1mVery.draw(rect)
      line1mGood.draw(rect)
      line1mNeeds.draw(rect)

      line5mBest.draw(rect)
      line5mVery.draw(rect)
      line5mGood.draw(rect)
      line5mNeeds.draw(rect)
   }
}

class PieValues {

   let start: CGFloat
   let arc: CGFloat
   let sliceRadius: CGFloat
   let color: UIColor

   init?(start: Double, arc: Double, sliceRadius: Double, color: UIColor) {

      guard start >= 0.0, start <= 360.0 else {
         return nil
      }

      guard arc >= 0.0, arc <= 360.0 else {
         return nil
      }

      // This value must be between 0 and 1
      guard sliceRadius >= 0.0, sliceRadius <= 1.0 else {
         return nil
      }

      self.start = PieValues.getRadians(from: start)
      self.arc = PieValues.getRadians(from: arc)
      self.sliceRadius = CGFloat(sliceRadius)
      self.color = color
   }

   private static func getRadians(from degrees: Double) -> CGFloat {
      let radians: Double = degrees * .pi / 180.0
      return CGFloat(radians)
   }
}

class PieSlice {

   private let values: PieValues?

   init(_ values: PieValues?) {
      self.values = values
   }

   func draw(_ rect: CGRect) {

      // Values object must be valid...
      guard let values = values else {
         return
      }

      // This view can be resized in any way, so we take the min length as diameter, to avoid graph being cut off
      let graphSize = rect
      let graphCenter = CGPoint(x: graphSize.width / 2.0, y: graphSize.height / 2.0)
      let graphDiameter: CGFloat = min(graphSize.width, graphSize.height) * values.sliceRadius
      let graphRadius: CGFloat = graphDiameter / 2.0

      // Lets calculate the values to create the pie...
      let pieRadius: CGFloat = graphRadius / 2.0
      let pieStart = values.start
      let pieEnd = values.start + values.arc

      // Draws the pie
      let pie = UIBezierPath(arcCenter: graphCenter, radius: pieRadius, startAngle: pieStart, endAngle: pieEnd, clockwise: true)
      pie.lineWidth = graphRadius
      values.color.setStroke()
      pie.stroke()
   }
}

class PieArc {

   private let values: PieValues?
   private let lineWidth: Int

   init(_ values: PieValues?, lineWidth: Int) {
      self.values = values
      self.lineWidth = lineWidth
   }

   func draw(_ rect: CGRect) {

      // Values object must be valid...
      guard let values = values else {
         return
      }

      // This view can be resized in any way, so we take the min length as diameter, to avoid graph being cut off
      let graphSize = rect
      let graphCenter = CGPoint(x: graphSize.width / 2.0, y: graphSize.height / 2.0)
      let graphDiameter: CGFloat = min(graphSize.width, graphSize.height) * values.sliceRadius
      let graphRadius: CGFloat = graphDiameter / 2.0

      // Lets calculate the values to create the pie...
      let pieRadius: CGFloat = graphRadius - CGFloat(lineWidth / 2)
      let pieStart = values.start
      let pieEnd = values.start + values.arc

      // Draws the farthest arc
      let pie = UIBezierPath(arcCenter: graphCenter, radius: pieRadius, startAngle: pieStart, endAngle: pieEnd, clockwise: true)
      pie.lineWidth = CGFloat(lineWidth)
      values.color.setStroke()
      pie.stroke()

      // We use the current point of the pie bezier path, to draw one of the radius lines
      let lineEnd = UIBezierPath()
      lineEnd.lineWidth = CGFloat(lineWidth)
      lineEnd.move(to: graphCenter)
      lineEnd.addLine(to: pie.currentPoint)
      lineEnd.stroke()

      // Now we create a path, similar to the one used to draw the pie, to position the draw point correctly
      let pieStartPoint = UIBezierPath(arcCenter: graphCenter, radius: pieRadius, startAngle: pieStart, endAngle: pieStart, clockwise: true)

      // Then we use that point to draw the second radius line
      let lineStart = UIBezierPath()
      lineStart.lineWidth = CGFloat(lineWidth)
      lineStart.move(to: graphCenter)
      lineStart.addLine(to: pieStartPoint.currentPoint)
      lineStart.stroke()
   }
}