> On Sep 29, 2016, at 8:14 PM, Xiaodi Wu via swift-evolution > <swift-evolution@swift.org> wrote: > > I'm confused by this explanation.Today, `type(of:)` is the new > `.dynamicType`. Is this proposal suggesting a silent change so that it now > returns the static type? If so, why (particularly when you explain that this > is often *not* what you would want)?
I'm short-handing the names to talk about the return values. In other words, I assume that, if we have both `type(of:)` and `subtype(of:)`, their signatures would be: func type<T>(of: T) -> Type<T> func subtype<T>(of: T) -> Subtype<T> And I'm saying that, given these names, `type(of:)` is confusing and near-useless, whereas `subtype(of:)` is what you almost always want. We *could*, of course, have a function called `type(of:)` which returned `Subtype<T>` and had the semantics I'm referring to as `subtype(of:)`. A name is just a name. > I'm also somewhat puzzled about the proposed design. This proposal explains > that Subtype<T> should be a supertype of Type<T> and its subtypes. Why is a > supertype named Subtype? Because a type's name should describe the *instances*; that's why you don't put "Class" at the end of all of your class names. (It's also why we're proposing `Type<T>` instead of `Metatype<T>`.) Every instance of `Subtype<T>` is the type instance for a subtype of `T`. For instance, in this hierarchy: NSObject NSResponder: NSObject NSView: NSResponder `Type<NSResponder>` is a `Subtype<NSObject>`, but not a `Subtype<NSView>`. Thus, this reads correctly: let aType: Subtype<NSResponder> = NSView.self Whereas this does not: let aType: Supertype<NSResponder> = NSView.self -- Brent Royal-Gordon Architechies _______________________________________________ swift-evolution mailing list swift-evolution@swift.org https://lists.swift.org/mailman/listinfo/swift-evolution