如何使用 swift iOS 9 绘制半圆并基于一个值绘制角度并用颜色填充该部分

我想画两个半圆，如下图所示（下图）

I'm trying it but did not get anything. Tried some chart api and a few code to draw pie chart from stackoverflow but they need to edit and I don't know about Core Graphics. I am working on Xcode 7.3.1 and iOS 9.

我的问题是：
如何绘制一个半圆，该半圆采用一个值并首先转换该值以获得其等效角度，然后绘制该角度的圆弧并在该部分填充颜色？

以下代码在 XCode iOS Playground 中运行。它创建了一个自定义UIView类并绘制两个饼图。起始角度和结束角度以整圆的百分比指定。

您可以根据您拥有的数据轻松扩展它以显示更多或更少的切片。

The drawRect方法创建一条从中心开始的贝塞尔曲线路径，然后添加一个圆弧段，最后闭合该路径以便对其进行填充。

Xcode 10.2.1/Swift 4.2 更新

class PieChart : UIView {

    override func draw(_ rect: CGRect) {

        drawSlice(rect: rect, startPercent: 0, endPercent: 50, color: .green)
        drawSlice(rect: rect, startPercent: 50, endPercent: 75, color: .red)
    }

    private func drawSlice(rect: CGRect, startPercent: CGFloat, endPercent: CGFloat, color: UIColor) {
        let center = CGPoint(x: rect.origin.x + rect.width / 2, y: rect.origin.y + rect.height / 2)
        let radius = min(rect.width, rect.height) / 2
        let startAngle = startPercent / 100 * CGFloat.pi * 2 - CGFloat.pi
        let endAngle = endPercent / 100 * CGFloat.pi * 2 - CGFloat.pi
        let path = UIBezierPath()
        path.move(to: center)
        path.addArc(withCenter: center, radius: radius, startAngle: startAngle, endAngle: endAngle, clockwise: true)
        path.close()
        color.setFill()
        path.fill()
    }
}

let pieChart = PieChart(frame: CGRect(x: 0.0, y: 0.0, width: 300.0, height: 300.0))
pieChart.backgroundColor = .clear

未命名的早期版本

import UIKit

class PieChart : UIView {

    override func drawRect(rect: CGRect) {

        drawSlice(rect, startPercent: 0, endPercent: 50, color: UIColor.greenColor())
        drawSlice(rect, startPercent: 50, endPercent: 75, color: UIColor.redColor())
    }

    private func drawSlice(rect: CGRect, startPercent: CGFloat, endPercent: CGFloat, color: UIColor) {
        let center = CGPoint(x: rect.origin.x + rect.width / 2, y: rect.origin.y + rect.height / 2)
        let radius = min(rect.width, rect.height) / 2
        let startAngle = startPercent / 100 * CGFloat(M_PI) * 2 - CGFloat(M_PI)
        let endAngle = endPercent / 100 * CGFloat(M_PI) * 2 - CGFloat(M_PI)
        let path = UIBezierPath()
        path.moveToPoint(center)
        path.addArcWithCenter(center, radius: radius, startAngle: startAngle, endAngle: endAngle, clockwise: true)
        path.closePath()
        color.setFill()
        path.fill()
    }
}

let pieChart = PieChart(frame: CGRect(x: 0.0, y: 0.0, width: 300.0, height: 300.0))
pieChart.backgroundColor = UIColor.clearColor()