Change a label on hover

Please explain exactly what you did, eventually post the code.

- You created a new class definition in XCode, from File menu:

File > New > File

- Select MacOS and Cocoa class

- Subclass of NSTextField

- name LabelWithHelp

Is it how you proceeded ?

You should have got a new file with the following content

import Cocoa

class LabelClass: NSTextField {

    override func draw(_ dirtyRect: NSRect) {
        super.draw(dirtyRect)

        // Drawing code here.
    }
   
}

Now replace the content with the following (I have corrected a few errors)

import Cocoa

class LabelWithHelp: NSTextField {
   
    var textForHover = "Some new text"     // This will be changed as needed
    var nonHoverText : String?
   
    override func draw(_ dirtyRect: NSRect) {
        super.draw(dirtyRect)
        // Drawing code here. If needed
    }
   
    // MARK: - Mouse Events
   
    // --------------------- mouseEntered --------------------------------------------------------------
    //  Description: When hovering over label
    //  Parameters
    //      theEvent: NSEvent
    //  Comments :
    //      Need to have defined trackingArea
    // -------------------------------------------------------------------------------------------------
   
    override func mouseEntered(with theEvent: NSEvent) {
       
        super.mouseEntered(with: theEvent)
        nonHoverText = self.stringValue     // Save the actual content
        self.stringValue = textForHover     // replace in label
    }
   
    // --------------------- mouseExited --------------------------------------------------------------
    //  Description: Exit from hover
    //  Parameters
    //      theEvent: NSEvent
    //  Comments :
    // -------------------------------------------------------------------------------------------------
   
    override func mouseExited(with theEvent: NSEvent) {
        super.mouseExited(with: theEvent)
        self.stringValue = nonHoverText ?? ""     // replace with original text
    }
   }

In the view, in IB, create a label

Change its type to LabelWithHelp

In the ViewController where the label is:

- declare an IBOutlet for the label and a tracking area

    @IBOutlet weak var label: LabelWithHelp!

    fileprivate var labelTrackingArea    : NSTrackingArea?

Connect the IBOutlet to the label in IB

- in viewDidload, set the tracking area:

            labelTrackingArea = NSTrackingArea(rect: label.bounds, options: [NSTrackingArea.Options.mouseEnteredAndExited, NSTrackingArea.Options.cursorUpdate, NSTrackingArea.Options.activeInKeyWindow], owner: label, userInfo: nil)
            label.addTrackingArea(labelTrackingArea!)

Run

You should see the label change when you hover on it and return to its value when exiting.