From: dblack@...
Date: 2006-04-11T10:48:59+09:00
Subject: Re: Class Definition inside a method definition?

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Hi --

On Tue, 11 Apr 2006, David Vallner wrote:

> D=C5=88a Utorok 11. Apr=C3=ADl 2006 02:39 Bihal nap=C3=ADsal:
>> Thanks David. I'm not sure you caught sight of the line of code I was
>> worried about. I should have made it more clear. This one in particular
>>
>> sclass =3D class << self; self; end
>>
>> does use a class keyword and syntactic construct, it's just on a single
>> line.
>>
>> Bihal
>
> Well, "class << self" isn't really a class definition, it's a change of s=
cope
> into an object's singleton class.

It's still a class definition block -- it's just that the class is
identified with the << obj construct rather than a simple constant
name.  The class keyword takes either form, but it's still basically
doing the same thing.

> It just looks a real awful lot like one ;P
> Which might, or might not exist at the time, and in the latter case it
> indeeds starts to exist. I'm also possibly very wrong, but I've been able=
 to
> live with understanding this that way ;P
>
> Also, Pickaxe seems mildly wrong about the instance method definition bit=
:
>
> irb(main):001:0> class Foo
> irb(main):002:1>   def bar
> irb(main):003:2>     def quux
> irb(main):004:3>       puts "Foo#quux"
> irb(main):005:3>     end
> irb(main):006:2>   end
> irb(main):007:1> end
> =3D> nil
> irb(main):008:0> foo =3D Foo.new
> =3D> #<Foo:0xb7caf8c8>
> irb(main):009:0> foo.quux
> NoMethodError: undefined method `quux' for #<Foo:0xb7caf8c8>
>        from (irb):9
>        from :0
> irb(main):010:0> foo.bar
> =3D> nil
> irb(main):011:0> foo.quux
> Foo#quux
> =3D> nil
> irb(main):012:0> Foo.new.quux
> Foo#quux
> =3D> nil
>
> Is that 1st ed. or 2nd ed. you're quoting? Might have changed between Rub=
y 1.6
> and 1.8.

It did change in that span.


David

--=20
David A. Black (dblack@wobblini.net)
Ruby Power and Light, LLC (http://www.rubypowerandlight.com)

"Ruby for Rails" coming in PDF April 15, and in paper May 5!
http://www.manning.com/black
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