[Pitch #2] Property Delegates by Custom Attributes

Evolution Pitches
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Just to clarify a few things:

  • The restriction for a property delegate type to have a single generic type parameter is now lifted? (Edit: I checked the tests in the new implementation and can confirm this restriction is gone. :tada:)

    And thank you so much for allowing explicitly providing generic type parameter list on the property delegate (@Lazy<Int> var property: Int) - I assume that will also play nicely in a generic context.

    (Edit: You replied in the other thread, but I didn't get a notification.)

  • Now that property delegates are custom attributes, do you have a vision what can/should happen next with the IB prefixed attributes? Those are part of the language if I'm not mistaken but they should really be part of UIKit/AppKit. One thing that concerns me a little is that @IBOutlet requires the type to be an optional. As a property delegate it could be similar to DelayedMutable.

  • Can you also clarify in the proposal how the API surface marked with property delegates will look for imported API?

    I assume @propertyDelegate attribute itself will be always visible on public types (trivial), but what about properties annotated with a concrete delegate.

    Is this a correct assumption?

    // module A
@Lazy
public var foo: Int = 1738

// for the API user the above is exposed as following
// when module A is imported
public var foo: Int = 1738

  • One other thought: I hope the tooling can teached to jump to the property delegate type declaration when for example in Xcode you would cmd + click on the property delegate.

Small correction, BehaviorRelay is part of RxCocoa which is build as a common extension of RxSwift. That makes BehaviorRelay a safe wrapper around BehaviorSubject that has similar semantics except that it also can be disposed or error out. You can change RxSwift's BehaviorRelay replays to RxCocoa's BehaviorRelay replays. ;)

Other than that I love the direction the proposal is going now, it shaped into something really swifty.

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