Slider resizing image view

Question

I'm trying to make a slider resize my images and center them into a view. I've tried all kinds of stuff, but am left with this after deleting all the non working code. I have the image Horizontal and Vertically lined up with constraints in the storyboard, but doesn't seem to help. Here is the crappy code I have.

@IBAction func sizeSlider(_ sender: UISlider) {
    
    let value = Int(sender.value)
    var sizeValue:Int = 200
    
    switch value {
    case 0...1:
        sizeLabel.text = "100x100"
        sizeValue = 100
    case 2:
        sizeLabel.text = "150x150"
        sizeValue = 150
    case 3:
        sizeLabel.text = "200x200"
        sizeValue = 200
    case 4:
        sizeLabel.text = "250x250"
        sizeValue = 250
    case 5:
        sizeLabel.text = "300x300"
        sizeValue = 300
    default:
        print("Error")
    }
    
    dartBoardImage.frame.size.width = CGFloat(sizeValue)
    dartBoardImage.frame.size.height = CGFloat(sizeValue)
}

Answer 1

"I have the image Horizontal and Vertically lined up with constraints in the storyboard"

You cannot mix auto-layout (constraints) with explicit frame changes.

What you (probably) want to do is...

In Storyboard:

• give your dartBoardImage image view a Width constraint of 100
• also give it an Aspect Ratio constraint of 1:1 ... that will keep it's height equal to its width
• constrain it centered in your view

Now, Ctrl-Drag from the Width constraint to your class code, and create an outlet for it:

@IBOutlet var imageWidthConstraint: NSLayoutConstraint!

Your slider code will now change that constraint's .constant property to update the size:

imageWidthConstraint.constant = CGFloat(sizeValue)

So, your full sizeSlider func becomes:

@IBAction func sizeSlider(_ sender: UISlider) {
    
    let value = Int(sender.value)
    var sizeValue:Int = 200
    
    switch value {
    case 0...1:
        sizeLabel.text = "100x100"
        sizeValue = 100
    case 2:
        sizeLabel.text = "150x150"
        sizeValue = 150
    case 3:
        sizeLabel.text = "200x200"
        sizeValue = 200
    case 4:
        sizeLabel.text = "250x250"
        sizeValue = 250
    case 5:
        sizeLabel.text = "300x300"
        sizeValue = 300
    default:
        print("Error")
    }
    
    // change the image view's width constraint
    imageWidthConstraint.constant = CGFloat(sizeValue)
    
    // don't do this
    //dartBoardImage.frame.size.width = CGFloat(sizeValue)
    //dartBoardImage.frame.size.height = CGFloat(sizeValue)
}