Adding and removing NSTextField programatically in SWIFT OS X - macos

Question

I am trying to write text labels on a graph view representing a variety of data points (imagine a line graph in Excel).
I select a data set using a tableView. Each time a select a new data set the graph is redrawn.
I can draw the line graph using a custom view. No problems.
I can draw the text labels using the following function called from drawRect():
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)
}
}
}
However, I can not work out how to remove the data labels when the view is updated and a new data set presented. The graph redraws but the text labels remain from the previous data set.
Any guidance/suggestions would be appreciated.

Answer 1

Adding the following code to the top of the function has solved the issue for me.
let subViewsToRemove = self.subviews
for object in subViewsToRemove {
object.removeFromSuperview()
}