why my stepper does't give the correct value when I tap the increment button?

Question

I am using kw stepper pod, since it is customizable. I can separate the increment button, decrement button and using my own label. but the behaviour should be the same as UIStepper

that is what it looks like, it consists of 1 increment button, 1 decrement button and counter label.

here is the code on my view controller:

import UIKit
import KWStepper

class ViewController: UIViewController {

    @IBOutlet weak var counterLabel: UILabel!
    @IBOutlet weak var decrementButton: UIButton!
    @IBOutlet weak var incrementButton: UIButton!

    var stepper: KWStepper!

    override func viewDidLoad() {
        super.viewDidLoad()

        stepper = KWStepper(decrementButton: decrementButton, incrementButton: incrementButton)
        stepper.autoRepeat = false
        stepper.autoRepeatInterval = 1
        stepper.wraps = false
        stepper.minimumValue = 0
        stepper.maximumValue = 100
        stepper.incrementStepValue = 1
        stepper.decrementStepValue = 1
        stepper.value = 0.0

        counterLabel.text = "\(stepper.value)"


    }

    @IBAction func incrementButtonDidTapped(_ sender: Any) {

        counterLabel.text = "\(stepper.value)"

    }


    @IBAction func decrementButtonDidTapped(_ sender: Any) {

        counterLabel.text = "\(stepper.value)"

    }
}

I connect the increment and decrement button using @IBAction touch up inside event.

so I expect when I tap the increment button, it will increase from 0,0 -> 1.0 -> 2.0 -> 3.0 and so on.

but in my case, when tap the increment button it will give 0,0 -> 0,0 -> 1,0 -> 2,0

the 0,0 will appear twice. why it appears twice ? how to solve this issue

I know that I can see the stepper value from value change event like this

stepper
    .valueChanged { stepper in
        // ...
    }

but I need to separate the event from increment and decrement button

here is the project on my google drive: https://drive.google.com/file/d/1IgeVW1OemRttoAOqJ6Ba8LpyZC_rc3-o/view?usp=sharing

Is this a separate issue from [your previous question](https://stackoverflow.com/questions/54148257/why-my-stepper-value-inside-collection-view-cell-doesnt-change)? — rmaddy, Jan 12 '19 at 04:57

Mayank K Rastogi · Accepted Answer · 2019-01-12T05:17:23.770

The incrementButtonDidTapped and decrementButtonDidTapped methods are possibly being called before stepper.value changes, since KWStepper also listens for touchUpInside events from both of these buttons to change its value.

KWStepper exposes two properties decrementCallback and incrementCallback which you can use to get notified when the value gets decremented/incremented. You can use these instead of an IBAction on the two buttons.

stepper.decrementCallback = { (stepper) in
    self.counterLabel.text = "\(stepper.value)"
}

stepper.incrementCallback = { (stepper) in
    self.counterLabel.text = "\(stepper.value)"
}

Alternatively, you can confirm to KWStepperDelegate and implement KWStepperDidIncrement and KWStepperDidDecrement delegate methods to get notified.

import UIKit
import KWStepper

class ViewController: UIViewController, KWStepperDelegate {

    @IBOutlet weak var counterLabel: UILabel!
    @IBOutlet weak var decrementButton: UIButton!
    @IBOutlet weak var incrementButton: UIButton!

    var stepper: KWStepper!

    override func viewDidLoad() {
        super.viewDidLoad()

        stepper = KWStepper(decrementButton: decrementButton, incrementButton: incrementButton)
        stepper.autoRepeat = false
        stepper.autoRepeatInterval = 1
        stepper.wraps = false
        stepper.minimumValue = 0
        stepper.maximumValue = 100
        stepper.incrementStepValue = 1
        stepper.decrementStepValue = 1
        stepper.value = 0.0

        // Set the delegate
        stepper.delegate = self

        counterLabel.text = "\(stepper.value)"


    }

    @objc func KWStepperDidIncrement() {
        counterLabel.text = "\(stepper.value)"
    }


    @objc func KWStepperDidDecrement() {
        counterLabel.text = "\(stepper.value)"
    }
}

the first approach using stepper.decrementCallback is the correct answer, but it doesn't work when I try using KWStepper delegate. thanks :) — Alexa289, Jan 12 '19 at 05:34
@Alexa289 it should have worked. Did you set the `stepper.delegate = self` in `viewDidLoad()`? — Mayank K Rastogi, Jan 12 '19 at 05:43

score 0 · Answer 2 · answered Jan 12 '19 at 04:56

0

You can replace your click events with following code

@IBAction func incrementButtonDidTapped(_ sender: Any) {

    stepper.valueChanged { (steper) in
        self.counterLabel.text = "\(steper.value)"
    }

}


@IBAction func decrementButtonDidTapped(_ sender: Any) {

    stepper.valueChanged { (steper) in
        self.counterLabel.text = "\(steper.value)"
    }

}

answered Jan 12 '19 at 04:56

Anji Mendpara

90
8

So an explanation of the problem is that the label was being changed after the button was tapped, but BEFORE the value was changed? – Nate Jan 12 '19 at 04:58

why my stepper does't give the correct value when I tap the increment button?

2 Answers2