> On Mar 14, 2017, at 1:02 AM, Andrew Thompson via swift-evolution
> <[email protected]> wrote:
>
> Hello Swift Evolution Community,
>
> I’ve been thinking about a new language feature that would allow properties
> to be first class citizens. The basic idea is as follows:
>
> let x: PropertySelector<UIView, CGFloat> =
> #property(UIView.frame.origin.x)
> let view: UIView = …
> view.frame.origin.x = 20
> x.read(view) // returns 20
> x.write(view, value: 9091)
> view.frame.origin.x // now 9091
>
> This is a trivial example, but now we can do more interesting things in our
> code. For example, we can animate any property on a view (that is documented
> to be animatable of course):
>
> func animate(view: UIView, property: PropertySelector<UIView, CGFloat>,
> amount: Int) {
> let originalValue = property.read(view)
> func generateKeyFrames() {
> let step = 1.0 / Double(amount)
> for i in 0..<amount {
> let newValue = originalValue + CGFloat(i)
> let time = Double(i) / Double(amount)
> UIView.addKeyframe(withRelativeStartTime: time,
>
> relativeDuration: step,
> animations: {
> property.write(view, value: newValue) }
> )
> }
> }
>
> UIView.animateKeyframes(withDuration: 1.0,
> delay: 0,
> options: [],
> animations:
> generateKeyFrames,
> completion: nil)
> }
>
> let myView: UIView = …
> myView.frame = CGRect(x: 20, y: 100, width: 99, height: 120)
>
> // once this completes, myView.frame.origin.x == 120
> animate(view: myView, property: #property(UIView.frame.origin.x),
> amount: 100)
>
> // once this completes, myView.frame.size.width == 198
> animate(view: myView, property: #property(UIView.frame.size.width),
> amount: 99)
>
> I think this would be a pretty neat feature to have, what do you think?
We agree! How does this sound:
https://lists.swift.org/pipermail/swift-evolution/Week-of-Mon-20170313/033998.html
<https://lists.swift.org/pipermail/swift-evolution/Week-of-Mon-20170313/033998.html>
-Joe
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