CODEWITHSUNDEEP
iosswift
Cesare
Cesare

Reputation: 9409

I can't understand why this if statement doesn't work in Swift

My app involves two UILabels labelDisplay and labelStatus, one UIButton, buttonAddOne, and a variable numbers. I can't understand why the labelStatus isn't being updated when numbers reaches 5.

import UIKit

var numbers:Int = 0

class ViewController: UIViewController {

    // Declaration of the two labels
    @IBOutlet weak var labelDisplay: UILabel!
    @IBOutlet weak var labelStatus: UILabel!

    // Code for the "Add 1" button
    @IBAction func buttonAddOne(sender: AnyObject) {
        numbers = numbers + 1
        labelDisplay.text = "\(numbers)"
    }

    override func viewDidLoad() {
        super.viewDidLoad()

        if numbers == 5 {
            labelStatus.text = "Numbers variable is equal to 5! Hurray!"
        }
    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
    }
}

Upvotes: 0

Views: 110

Answers (2)

Antonio
Antonio

Reputation: 72750

The code you put in viewDidLoad is executed once, when the view is loaded - it isn't triggered every time numbers is updated.

To implement what you need, you should make number an instance property, and add a didSet observer:

class ViewController: UIViewController {
    var numbers: Int = 0 {
        didSet {
            if numbers == 5 {
                labelStatus.text = "Numbers variable is equal to 5! Hurray!"
            }
        }
    }
    ...
}

The property observer is automatically executed when the property value is changed.

For more info read Property Observers

Upvotes: 1

matt
matt

Reputation: 534950

I can't understand why the labelStatus isn't being updated when "numbers" reaches 5

What would update it? The code inside viewDidLoad? But viewDidLoad is called once, early, when the view controller gets its view; it will never be called again, so that code will never run again.

If you want to update labelStatus, why don't you do it in the same code that increments numbers?

@IBAction func buttonAddOne(sender: AnyObject) {
    numbers = numbers + 1
    labelDisplay.text = "\(numbers)"
    if numbers == 5 {
        labelStatus.text = "Numbers variable is equal to 5! Hurray!"
    }
}

Upvotes: 1

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