Why can’t we have these kinds of globals?

[CTMacUser (Daryle Walker)]

Why can’t I declare a type-level property for a generic nominal (value?) type? Why can’t we define a static variable inside a (generic?) function?

[xwu (Xiaodi Wu)]

Vide:

Static/Class stored properties in generic types?

I'm attempted to create an observables system that can be updated and subscribed to generically. I use something like this: final class Observer<Value> { } protocol Observable { associated type Value static var observable: Observer<Value> } And I can use it fine with normal types: struct Model: Observable { static let observable = Observer<Model>() } But attempting to make generic types conform: final class Future<Value> { static let observable = Observer<Future<Value>>() }…

@Joe_Groff

I don't recall any discussions about whether it's a good idea to support; the lack of implementation is the only barrier I know of.

[Nevin]

@CTMacUser

Why can’t we define a static variable inside a (generic?) function?

Swift has never supported static variables in functions. I believe this was a deliberate design choice, but I have not seen any discussion about it.

Regardless, for non-generic functions, you can easily achieve the same effect with a static variable on a type declared within the function:

func foo() {
  struct Foo { static var x = 0 }
  Foo.x += 1
  print(Foo.x)
}

[nuclearace (Erik Little)]

@Nevin

Swift has never supported static variables in functions. I believe this was a deliberate design choice, but I have not seen any discussion about it.

Probably because they have an extremely limited number of uses. And I'd say most of those uses are better served by alternative designs.