如何使用 CorePlot 框架和 swift 3 制作折线图？

Question

我不明白如何使用 CorePlot 2.2 和 Swift 3（Xcode 8、iOS 10）制作线图。

有人能解释一下怎么做吗？

特别是，我不明白最后一个函数numbers（第 97-103 行（最后几行））是如何工作的：

    import UIKit
import CorePlot

class dottedLine: UIViewController {
    @IBOutlet var hostView: CPTGraphHostingView!

    var plot: CPTScatterPlot!


    override func viewDidLayoutSubviews() {
        super.viewDidLayoutSubviews()
        initPlot()
    }



    let xValues: [NSNumber] = [1,2,3,4]
    let yValues: [NSNumber] = [1,5,4,3]

    func initPlot() {
        configureHostView()
        configureGraph()
        configureChart()
        configureAxes()
    }

    func configureHostView() {
        hostView.allowPinchScaling = false
    }

    func configureGraph() {
        // 1 - Create the graph
        let graph = CPTXYGraph(frame: hostView.bounds)
        graph.plotAreaFrame?.masksToBorder = false
        hostView.hostedGraph = graph

        // 2 - Configure the graph
        //graph.apply(CPTTheme(named: CPTThemeName.plainWhiteTheme))
        //graph.fill = CPTFill(color: CPTColor.clear())
        graph.paddingBottom = 30.0
        graph.paddingLeft = 30.0
        graph.paddingTop = 0.0
        graph.paddingRight = 0.0


        // 3 - Set up styles
        let titleStyle = CPTMutableTextStyle()
        titleStyle.color = CPTColor.black()
        titleStyle.fontName = "HelveticaNeue-Bold"
        titleStyle.fontSize = 16.0
        titleStyle.textAlignment = .center
        graph.titleTextStyle = titleStyle

        let title = "Just title"
        graph.title = title
        graph.titlePlotAreaFrameAnchor = .top
        graph.titleDisplacement = CGPoint(x: 0.0, y: -16.0)

        // 4 - Set up plot space
        let xMin = 0.0
        let xMax = 5.0
        let yMin = 0.0
        let yMax = 15.0
        guard let plotSpace = graph.defaultPlotSpace as? CPTXYPlotSpace else { return }
        plotSpace.xRange = CPTPlotRange(locationDecimal: CPTDecimalFromDouble(xMin), lengthDecimal: CPTDecimalFromDouble(xMax - xMin))
        plotSpace.yRange = CPTPlotRange(locationDecimal: CPTDecimalFromDouble(yMin), lengthDecimal: CPTDecimalFromDouble(yMax - yMin))
    }

    func configureChart() {
        // 1 - Set up the plot
        plot = CPTScatterPlot()

        // 2 - Set up style
        let plotLineStile = CPTMutableLineStyle()
        plotLineStile.lineWidth = 1
        plotLineStile.lineColor = CPTColor.black()
        plot.dataLineStyle = plotLineStile

        // 3- Add plots to graph
        guard let graph = hostView.hostedGraph else { return }
        plot.dataSource = self
        plot.delegate = self
        graph.add(plot, to: graph.defaultPlotSpace)
    }

    func configureAxes() {
                }
    }



extension dottedLine: CPTScatterPlotDataSource, CPTScatterPlotDelegate {
    func numberOfRecords(for plot: CPTPlot) -> UInt {
        // number of points
        return UInt(xValues.count)
    }

    func scatterPlot(_ plot: CPTScatterPlot, plotSymbolWasSelectedAtRecord idx: UInt, with event: UIEvent) {
    }

   /* func numbers(for plot: CPTPlot, field fieldEnum: UInt, recordIndexRange indexRange: NSRange) -> [Any]? {
        print("xxxxxxx")
        switch CPTScatterPlotField(rawValue: Int(fieldEnum))! {
        case .X:
            return xValues[index] as NSNumber

        case .Y:
            return yValues[indexRange] as NSNumber
        }

    } */

   /* func symbols(for plot: CPTScatterPlot, recordIndexRange indexRange: NSRange) -> [CPTPlotSymbol]? {
        return xValues
    } */

    func number(for plot: CPTPlot, field: UInt, record: UInt) -> Any? {


        switch CPTScatterPlotField(rawValue: Int(field))! {
        case .X:
            return 2 as NSNumber

        case .Y:
            return 3 as NSNumber
        }
    }
}

Answer 1

对于散点图，此方法将针对每个索引处的 x 值和 y 值调用一次。

这是 DatePlot 示例应用程序中的方法：

func number(for plot: CPTPlot, field: UInt, record: UInt) -> Any?
{
    switch CPTScatterPlotField(rawValue: Int(field))! {
    case .X:
        return (oneDay * Double(record)) as NSNumber

    case .Y:
        return self.plotData[Int(record)] as NSNumber
    }
}