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iOS Build a Vending Machine App in Swift 2.0 Using the Vending Machine Updating the Quantity

David Lin
David Lin
35,864 Points

Vending Machine bug & fix: Stepper's value needs to be reset to 1 in reset()

There's a bug in the Vending Machine code as presented.


  1. Select an item.
  2. Increase the quantity by pressing "+" on the stepper to some greater value
  3. Switch selection to another item
  4. Increase the quantity by pressing "+" on the stepper to some greater value

Expected: After switching, the quantity of the new selection increments by 1 each time you press "+"

Actual: The quantity jumps up by the last quantity before switching selections. (e.g. If the last quantity was 3, then after pressing "+", the new quantity jumps from 1 to 4.)

Root Cause: The stepper's value was not reset to 1 after the selection switch, but remains at the last value before the switch.

Fix: Reset the stepper's value to 1 in reset()

  1. Hook up the stepper as an IBOutlet variable in the ViewController:

    @IBOutlet weak var stepper: UIStepper!
  2. Set the stepper's value to 1 in reset():

    func reset() {
        quantity = 1
        stepper.value = 1