From: Yehuda Katz <wycats@...>
Date: 2011-12-01T05:59:21+09:00
Subject: [ruby-core:41416] Re: [ruby-trunk - Bug #5690][Open] Module#qualified_const_get

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Yehuda Katz
(ph) 718.877.1325


2011/11/30 Yukihiro Matsumoto <matz@ruby-lang.org>

> Hi,
>
> In message "Re: [ruby-core:41408] Re: [ruby-trunk - Bug #5690][Open]
> Module#qualified_const_get"
>     on Wed, 30 Nov 2011 16:52:36 +0900, Yehuda Katz <wycats@gmail.com>
> writes:
>
> |> * is there any use-case for this method?
> |
> |We use it often in Rails.
>
> Could you show us the concrete example?  It is difficult for me to
> imagine.
>

One case is to convert path names (file system paths) into constants.

In general, Rails uses inflections to convert names from different
contexts. In the router, for instance, "foo/bar" is used to represent
namespaces, which are then converted into "Foo::Bar" and then Foo::Bar.


>
> |> * if Bar is not a class nor module, what kind error should be raised?
> |>
> |
> |TypeError: "(=85) is not a class/module"
>
> Understood.
>
> |> * is qualified_const_get an appropriate name for the function?
> |>
> |
> |Unknown. It's what we call it in Rails ;)
>
> How about
>
>  Foo.const_get("Bar::Baz")
>

Sounds good to me. Currently, trying to const_set or const_get a name with
:: in it produces a NameError, so it should not introduces new issues.


>
> or
>
>  Foo.const_get(:Bar, :Baz)
>

This doesn't satisfy the use-case in question.


>
> ?
>
>                                                        matz.
>
>

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<br clear=3D"all">Yehuda Katz<br>(ph) 718.877.1325<br>
<br><br><div class=3D"gmail_quote">2011/11/30 Yukihiro Matsumoto <span dir=
=3D"ltr">&lt;<a href=3D"mailto:matz@ruby-lang.org">matz@ruby-lang.org</a>&g=
t;</span><br><blockquote class=3D"gmail_quote" style=3D"margin:0 0 0 .8ex;b=
order-left:1px #ccc solid;padding-left:1ex;">

Hi,<br>
<br>
In message &quot;Re: [ruby-core:41408] Re: [ruby-trunk - Bug #5690][Open] M=
odule#qualified_const_get&quot;<br>
<div class=3D"im"> =A0 =A0on Wed, 30 Nov 2011 16:52:36 +0900, Yehuda Katz &=
lt;<a href=3D"mailto:wycats@gmail.com">wycats@gmail.com</a>&gt; writes:<br>
<br>
|&gt; * is there any use-case for this method?<br>
|<br>
|We use it often in Rails.<br>
<br>
</div>Could you show us the concrete example? =A0It is difficult for me to<=
br>
imagine.<br></blockquote><div><br></div><div>One case is to convert path na=
mes (file system paths) into constants.</div><div><br></div><div>In general=
, Rails uses inflections to convert names from different contexts. In the r=
outer, for instance, &quot;foo/bar&quot; is used to represent namespaces, w=
hich are then converted into &quot;Foo::Bar&quot; and then Foo::Bar.</div>

<div>=A0</div><blockquote class=3D"gmail_quote" style=3D"margin:0 0 0 .8ex;=
border-left:1px #ccc solid;padding-left:1ex;">
<div class=3D"im"><br>
|&gt; * if Bar is not a class nor module, what kind error should be raised?=
<br>
|&gt;<br>
|<br>
|TypeError: &quot;(=85) is not a class/module&quot;<br>
<br>
</div>Understood.<br>
<div class=3D"im"><br>
|&gt; * is qualified_const_get an appropriate name for the function?<br>
|&gt;<br>
|<br>
|Unknown. It&#39;s what we call it in Rails ;)<br>
<br>
</div>How about<br>
<br>
 =A0Foo.const_get(&quot;Bar::Baz&quot;)<br></blockquote><div><br></div><div=
>Sounds good to me. Currently, trying to const_set or const_get a name with=
 :: in it produces a NameError, so it should not introduces new issues.</di=
v>

<div>=A0</div><blockquote class=3D"gmail_quote" style=3D"margin:0 0 0 .8ex;=
border-left:1px #ccc solid;padding-left:1ex;">
<br>
or<br>
<br>
 =A0Foo.const_get(:Bar, :Baz)<br></blockquote><div><br></div><div>This does=
n&#39;t satisfy the use-case in question.</div><div>=A0</div><blockquote cl=
ass=3D"gmail_quote" style=3D"margin:0 0 0 .8ex;border-left:1px #ccc solid;p=
adding-left:1ex;">


<br>
?<br>
<br>
 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =
=A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0matz.<br>
<br>
</blockquote></div><br>

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