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Quentin Malgaud
Quentin Malgaud

Reputation: 415

Update storyboard constraint using code

I have a UIImage in code that I would like to enlarge vertically when a button is pressed. The UIImage is fully constrained in the storyboard and I would like to change its height when the button is pressed.

I have linked the UIImage and its height constraint in the code:

    @IBOutlet weak var botBotCons: NSLayoutConstraint!
    @IBOutlet weak var botBot: UIImageView!

Then 

@IBAction func testButton(sender: UIBarButtonItem) {
    println("testButton pressed")
    self.botBotCons.constant = 68   //or +=62 as its current constant is 6
    self.view.layoutIfNeeded()
}

I get the testButton pressed message in the console, but the image doesn't resize. What am I doing wrong? Do I need to change something in the storyboard as well?

Upvotes: 1

Views: 485

Answers (1)

Ptah
Ptah

Reputation: 976

You should to call layoutIfNeeded within the animation block. Apple actually recommends you call it once before the animation block to ensure that all pending layout operations have been completed. I just checked it with the resizing of button - everything works fine.

@IBOutlet weak var myBtn: UIButton!
@IBOutlet weak var btnHeight: NSLayoutConstraint!
@IBOutlet weak var btnWidth: NSLayoutConstraint!


@IBAction func resizeBtn(sender: AnyObject) {
    self.myBtn.titleEdgeInsets = UIEdgeInsetsMake(0, 0, 0, 0)

    self.view.layoutIfNeeded()
    self.btnHeight.constant += 50
    self.btnWidth.constant += 50

    UIView.animateWithDuration(0.7, animations: {
        self.view.layoutIfNeeded()
    })
}

P.S. make sure that other constraints don't block your changes.

Upvotes: 1

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