Default definitions with tags

[ilyapuchka]

Currently we can register few definitions with different tags and one with no tag, which will be used as a default if we try to resolve component using unknown tag.

But it does not work the other way - if we don't register definition without tag we will not be able to resolve component without providing tag.

Would it be useful to be able to setup definition with tag as a default and later be able to resolve it without setting tag?

container.register(tag: "facebook", useByDefault: true) { FacebookOAuth() as OAuth }
container.register(tag: "twitter") { TwitterOAuth() as OAuth }
container.register(tag: "google") { GoogleOAuth() as OAuth }

container.resolve() as OAuth // will resolve FacebookOAuth

container.register() { TwitterOAuth() as OAuth } // will override previous default
container.resolve("tumblr") as OAuth // should not resolve, because user explicitly specified unknown tag

[AliSoftware]

Interesting idea but I don't think it's worth it. one can simply register the same block with both the tag and nil if they want that behavior.
I think that kind of logic belong to each application's code anyway and is not worth adding a parameter (even optional) for that marginal case.

[AliSoftware]

One way people could do it in their project on their own:

let defaultFactory = { FacebookOAuth() as OAuth }
container.register(factory: defaultFactory) 
container.register(tag: "Facebook", factory: defaultFactory)
container.register(tag: "twitter") { TwitterOAuth() as OAuth }
container.register(tag: "google") { GoogleOAuth() as OAuth }

Alternate way:

container.register(tag: "Facebook") { FacebookOAuth() as OAuth }
container.register(tag: "twitter") { TwitterOAuth() as OAuth }
container.register(tag: "google") { GoogleOAuth() as OAuth }
container.register() { [unowned container] in container.resolve("Facebook") as OAuth }

(Both are untested code, just ideas typed live in GitHub)

[ilyapuchka]

Yes, probably that could add additional confusion about what definition will be used without any big win.