NSProgressIndicator bindings don't do anything

Question

Created Apr ’24

Replies 3

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Participants 2

I'm trying to bind a NSProgressIndicator to Progress, but with the following code I only get an indeterminate progress indicator with a blue bar forever bouncing left and right, even after the two timers fire. According to the documentation:

Progress is indeterminate when the value of the totalUnitCount or completedUnitCount is less than zero or if both values are zero.

What am I doing wrong?

class ViewController: NSViewController {
    
    let progress = Progress()

    override func loadView() {
        view = NSView(frame: CGRect(x: 0, y: 0, width: 500, height: 500))
        let progressIndicator = NSProgressIndicator(frame: CGRect(x: 100, y: 100, width: 100, height: 100))
        progressIndicator.bind(.isIndeterminate, to: progress, withKeyPath: "isIndeterminate")
        progressIndicator.bind(.value, to: progress, withKeyPath: "completedUnitCount")
        progressIndicator.bind(.maxValue, to: progress, withKeyPath: "totalUnitCount")
        progressIndicator.startAnimation(nil)
        view.addSubview(progressIndicator)
        
        progress.completedUnitCount = 3
        progress.totalUnitCount = 10
        Timer.scheduledTimer(withTimeInterval: 1, repeats: false) { _ in
            print(1)
            self.progress.completedUnitCount = 6
        }
        Timer.scheduledTimer(withTimeInterval: 6, repeats: false) { _ in
            print(2)
            self.progress.completedUnitCount = 0
            self.progress.totalUnitCount = 0
        }
    }

}

Answered by xhruso00 in 789201022

You did your bindings wrongly. The KVO should be done on "indeterminate" instead of "isIndeterminate"

progressIndicator.bind(.isIndeterminate, to: progress, withKeyPath: "indeterminate")

Boost

Answer 1

xhruso00 OP

May ’24

Accepted Answer

You did your bindings wrongly. The KVO should be done on "indeterminate" instead of "isIndeterminate"

progressIndicator.bind(.isIndeterminate, to: progress, withKeyPath: "indeterminate")

0

Answer 2

xhruso00 OP

May ’24

From WWDC 2015 Session 232 Best Practices for Progress Reporting:

NSProgress properties are key value observable Add KVO observers to update your UI Not necessarily called on main thread.

I wouldn't risk doing bindings as it might crash your app.

0

Answer 3

Nickkk OP

Jun ’24

But according to Progress documentation::

Each of the properties of a progress object, including totalUnitCount, completedUnitCount, and fractionCompleted, support key-value observing (KVO). This makes it extremely easy for a view or window controller object to observe the properties, and update UI elements, such as progress indicators, when the values change.

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