From: Aaron Patterson <tenderlove@...>
Date: 2011-12-01T10:04:00+09:00
Subject: [ruby-core:41419] Re: [ruby-trunk - Bug #5690][Open] Module#qualified_const_get


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On Wed, Nov 30, 2011 at 04:52:36PM +0900, Yehuda Katz wrote:
> On Tue, Nov 29, 2011 at 10:04 PM, Yukihiro Matsumoto <matz@ruby-lang.org>=
wrote:
>=20
> > Hi,
> >
> > In message "Re: [ruby-core:41404] [ruby-trunk - Bug #5690][Open]
> > Module#qualified_const_get"
> >     on Wed, 30 Nov 2011 12:10:02 +0900, Yehuda Katz <wycats@gmail.com>
> > writes:
> >
> > |It would be great if there was a way to dynamically load a constant pa=
th:
> > |
> > |  module Foo
> > |    module Bar
> > |      module Baz
> > |      end
> > |    end
> > |  end
> > |
> > |  Foo.qualified_const_get("Bar::Baz") =3D> Foo::Bar::Baz
> >
> > Interesting.
> >
> > * is there any use-case for this method?
> >
>=20
> We use it often in Rails.

When serializing objects to yaml, the fully qualified class name is=20
emitted.  When reviving those objects, the class name comes back as a=20
string, so psych uses rb_path2class to find the constant.

> > * if Bar is not a class nor module, what kind error should be raised?
> >
>=20
> TypeError: "(=E2=80=A6) is not a class/module"

Agreed.

> > * is qualified_const_get an appropriate name for the function?
> Unknown. It's what we call it in Rails ;)

Yes.

--=20
Aaron Patterson
http://tenderlovemaking.com/

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