Completing Property Wrappers

[DevAndArtist (Adrian Meister)]

Future directions of Property Wrappers

The labels and the parameter names aren't perfectly aligned with the current design of property wrappers that is true. However wrapped wrappedKeyPath is still needed for a simple reason. You have to be able to disambiguate between the static subscript which returns the wrapped value vs. the static subscript that returns the projected value instead. I had some short conversations on Twitter with @Joe_Groff, @Douglas_Gregor and @jrose and I no longer think that the privately available feature sho…

And the rest of the thread.

Such design would also allow us to create property wrappers for computed properties.

One use case I have in mind:

extension EnvironmentValues {
  enum ValueKey: EnvironmentKey {
    static var defaultValue: Value { ... }
  }
​
  // before
  var value: Value {
    get {
      self[ValueKey.self]
    }
    set {
      self[ValueKey.self] = newValue
    }
  }

  // `Wrapper` is a static property wrapper which does not require any storage.
​
  // after
  @Wrapper(ValueKey.self)
  var value: Value
}

I would be against rushing to "complete" property wrappers any time soon, as this will dramatically change the design and property wrappers potential. I would like to encourage the community to push other language features that would make PW's even more powerful first.