> canImport (or whatever it ends up being called) is deliberate.
>
> You test before you import:
>
> #if canImport(x)
> import x
> #else
> ...
> #endif
>
> and you test at the use-site
>
> #if canImport(x)
> // use things that are available in x
> #else
> ...
>
> So you don't import UIKit unless you *can*, and you don't use UIColor unless
> you can import UIKit. This follows closely on the design of __has_include.
>
> -- E
I guess one issue I can see is it’s used in two different ways:
- The first use of canImport is used to check whether it can import a module,
and then does so, but there’s no requirement for it to do so. Is this the right
this to do?
- The second use of canImport makes no guarantee that the module has been
imported, only that it can.
What if instead `import` could return whether it imported or not, when used
with #if? Instead of ‘can import’, you get ‘did just import’ and ‘has imported’.
import Required // Error if not present, current behaviour
#if import CoolThing // Skips code block if not present, imports otherwise
// Do something with CoolThing module
#else
import AlmostAsCoolThing
#endif
and you test at the use-site
#if module(X) // Does not import, only checks if it has been imported
// use things that are available in X
#else
As per Pyry’s feedback, you could add a version:
#if import Frobnication(<1.7.3) // <- Only added version constraint here.
extension Knob : Frobnicatable { ... }
#endif
Just a way to make it less low level.
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