How to resize UIImageView based on UIImage's size/ratio in Swift 3?

Question

I have a UIImageView and the user is able to download UIImages in various formats. The issue is that I need the UIImageView to resize

Answer 1

The solution is also based on olearyj234's solution, but I think this will help more people.

@IBDesignable
class DynamicImageView: UIImageView {

    @IBInspectable var fixedWidth: CGFloat = 0 {
        didSet {
            invalidateIntrinsicContentSize()
        }
    }
    @IBInspectable var fixedHeight: CGFloat = 0 {
        didSet {
            invalidateIntrinsicContentSize()
        }
    }

    override var intrinsicContentSize: CGSize {
        var size = CGSize.zero
        if fixedWidth > 0 && fixedHeight > 0 { // 宽高固定
            size.width = fixedWidth
            size.height = fixedHeight
        } else if fixedWidth <= 0 && fixedHeight > 0 { // 固定高度动态宽度
            size.height = fixedHeight
            if let image = self.image {
                let ratio = fixedHeight / image.size.height
                size.width = image.size.width * ratio
            }
        } else if fixedWidth > 0 && fixedHeight <= 0 { // 固定宽度动态高度
            size.width = fixedWidth
            if let image = self.image {
                let ratio = fixedWidth / image.size.width
                size.height = image.size.height * ratio
            }
        } else { // 动态宽高
            size = image?.size ?? .zero
        }
        return size
    }

}