I have a generic type, and I want to add some methods that are available when
the type parameter is Bool. (This is in Xcode 8 beta 6, btw.)
public struct foo<T> {
...
}
extension foo where T: Bool {
…
}
The above fails to compile, with "type 'T' constrained to non-protocol type
‘Bool’”. Is that an error? The book doesn’t say that type constraints have to
be to protocols; in fact the example in the section “Type Constraint Syntax”
shows a type constraint that requires T to be a subclass of SomeClass.*
OK, so I’ll find a protocol for “boolean-like” values that’s implemented by
Bool. The Swift reference for `Bool` in Xcode doesn’t list anything.
Swiftdoc.org <http://swiftdoc.org/> shows a protocol `Boolean` that looks like
exactly what I want, but my compiler’s never heard of it; is this something
that snuck in post-3.0? If I switch Swiftdoc.org <http://swiftdoc.org/> back to
Swift 2.2, it shows an equivalent protocol called `BooleanType`, but if I try
to use that, the compiler says "'BooleanType' has been renamed to ‘Bool’”.
At this point I threw my laptop at the wall.
Not really, but I started to miss the stability and simplicity of C++… :-p
How the @$*% do I do this?
—Jens
* In fact the book never seems to talk about type constraints in generic type
extensions. It covers each of the two concepts, but not how to use them
together._______________________________________________
swift-users mailing list
swift-users@swift.org
https://lists.swift.org/mailman/listinfo/swift-users
