我正在尝试在表示各种数据点的图形视图上编写文本标签（想象一下Excel中的折线图）。
我使用tableView选择一个数据集。每次选择一个新的数据集时，图形将重新绘制。
我可以使用自定义视图绘制折线图。没问题
我可以使用以下从drawRect()调用的函数绘制文本标签：

func drawDataPointLabels(size: CGSize) {  //size is the view.bounds
    
    var dataLabelsArray: [(NSColor, String, NSRect)] = []
    
    // graphDetails contain an array of tuples  [(), (), (), ()] - this represents one graph type = eg Monthly Fees ** there will be a maximum of 12 items in the array
    for graphDetails in graphDetailsArray {
        
         // each dataPoint object is a tuple (graphType:  columnLabel: columnColor:  columnHeight:  columnNumber: ) representing one dataPoint
        for dataPoint in graphDetails {
            let graphHeight = size.height / 2
            let graphWidth = size.width - graphOrigin.x - rightMargin
            let columnAndGapSize = graphWidth / 25
            let labelX: CGFloat = (graphOrigin.x + columnAndGapSize) + (columnAndGapSize * dataPoint.columnNumber) * 2
            let labelY: CGFloat = dataPoint.columnHeight * (graphHeight - topMargin - bottomMargin)
            
            // determine the location and frame for the text label to match dataPoint
            let textFrame = NSRect(x: labelX, y: labelY, width: 30, height: 10)
            let dataPointTuple = (dataPoint.columnColor, dataPoint.columnLabel, textFrame)
            dataLabelsArray.append(dataPointTuple)
        }
        
        for dataPoint in dataLabelsArray {
            let (color, label, frameRect) = dataPoint
            let lblDataPoint = NSTextField(frame: frameRect)
            lblDataPoint.stringValue = label
            lblDataPoint.backgroundColor = backgroundColor
            lblDataPoint.textColor = color
            self.addSubview(lblDataPoint)
        }
    }
}

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但是，我不知道如何在视图更新和呈现新数据集时删除数据标签。图形将重新绘制，但文本标签仍保留以前的数据集。