From: Matthew Kerwin <matthew@...>
Date: 2013-04-11T20:26:38+09:00
Subject: Re: confusion with Struct class

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On Apr 11, 2013 8:19 PM, "Love U Ruby" <lists@ruby-forum.com> wrote:
>
> "Jes=FAs Gabriel y Gal=E1n" <jgabrielygalan@gmail.com> wrote in post
> #1105232:
> > On Thu, Apr 11, 2013 at 10:45 AM, Love U Ruby <lists@ruby-forum.com>
> > wrote:
> >>
> > If you read the doc you referenced closely:
> >
>  ***the name of this struct
> > will appear as a constant in class Struct***,
>
> Yes,I am confused how a full class be a constant. We can create a
> variable as a constant, say "NAME". class and module names are also
> constant. But full class body is constant - I just newly step into this
> topic.

Remember that all ruby values are objects, even classes.

    # classes
    class Foo; end
    Bar =3D class.new
    $baz =3D Foo
    qux =3D Bar

    # instance objects
    Foo.new
    Bar.new
    $baz.new
    qux.new

It's all, mostly, the same.

And a 'constant' is just a variable that gets a special warning when
assgined to, but aside from that it's not particularly magical.

    MyConst =3D []
    # all good:
    MyConst << 1
    MyConst.unshift 7
    MyConst.sort!
    MyConst.delete_if { |e| e<3 }
    def MyConst.foo; end
    # not good:
    MyConst =3D [7]

You can modify the _object_, but you can't modify the reference.

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<p>On Apr 11, 2013 8:19 PM, &quot;Love U Ruby&quot; &lt;<a href=3D"mailto:l=
ists@ruby-forum.com">lists@ruby-forum.com</a>&gt; wrote:<br>
&gt;<br>
&gt; &quot;Jes=FAs Gabriel y Gal=E1n&quot; &lt;<a href=3D"mailto:jgabrielyg=
alan@gmail.com">jgabrielygalan@gmail.com</a>&gt; wrote in post<br>
&gt; #1105232:<br>
&gt; &gt; On Thu, Apr 11, 2013 at 10:45 AM, Love U Ruby &lt;<a href=3D"mail=
to:lists@ruby-forum.com">lists@ruby-forum.com</a>&gt;<br>
&gt; &gt; wrote:<br>
&gt; &gt;&gt;<br>
&gt; &gt; If you read the doc you referenced closely:<br>
&gt; &gt;<br>
&gt; =A0***the name of this struct<br>
&gt; &gt; will appear as a constant in class Struct***,<br>
&gt;<br>
&gt; Yes,I am confused how a full class be a constant. We can create a<br>
&gt; variable as a constant, say &quot;NAME&quot;. class and module names a=
re also<br>
&gt; constant. But full class body is constant - I just newly step into thi=
s<br>
&gt; topic.</p>
<p>Remember that all ruby values are objects, even classes.</p>
<p>=A0=A0=A0 # classes<br>
=A0=A0=A0 class Foo; end<br>
=A0=A0=A0 Bar =3D class.new<br>
=A0=A0=A0 $baz =3D Foo<br>
=A0=A0=A0 qux =3D Bar</p>
<p>=A0=A0=A0 # instance objects<br>
=A0=A0=A0 Foo.new<br>
=A0=A0=A0 Bar.new<br>
=A0=A0=A0 $baz.new<br>
=A0=A0=A0 qux.new</p>
<p>It&#39;s all, mostly, the same.</p>
<p>And a &#39;constant&#39; is just a variable that gets a special warning =
when assgined to, but aside from that it&#39;s not particularly magical. </=
p>
<p>=A0=A0=A0 MyConst =3D []<br>
=A0=A0=A0 # all good:<br>
=A0=A0=A0 MyConst &lt;&lt; 1<br>
=A0=A0=A0 MyConst.unshift 7<br>
=A0=A0=A0 MyConst.sort!<br>
=A0=A0=A0 MyConst.delete_if { |e| e&lt;3 }<br>
=A0=A0=A0 def MyConst.foo; end<br>
=A0=A0=A0 # not good:<br>
=A0=A0=A0 MyConst =3D [7]</p>
<p>You can modify the _object_, but you can&#39;t modify the reference.</p>

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