How to adjust UIImageView margin programmatically with Swift

Question

I have a UIImageView as part of a UICollectionViewCell that I would like to use to visually display a quantity (like a progress bar). In this case the ImageView and its offset represent the percentage remaining of a given item represented by the cell.

Imagine an image of water inside a glass. When the glass is full you see all of the water texture. When the glass is half full, you see half of the water image. so on and so forth...

I want to adjust the top margin of the ImageView based on the percentage remaining. for example:

var image : UIImageView
var item = inventoriedItem(percentageRemaining : 100)

var pctLeft = item.percentageRemaining
pctLeft = 42

// PSEUDOCODE:
image.topMarginOffset = 100 - pctLeft

Answer 1

You could try adjusting the frame of the UIImageView based on the percentage left.

var image = UIImageView(frame: CGRect(x: 20, y: 10, width: 50, height: 100))
var pctLeft = 0.42

//assuming you want a vertical progress bar (like a glass of water).
image.frame = CGRect(x: 20, y: 10 + (100 * (1 - pctLeft)), width: 50, height: 100 * pctLeft)

Here I programmatically push the Y value down based on the reduced size of the bar. Let me know if this is what you were looking for...