Rails core - Jul 2007 - question about idiom for loading files in initializer.rb

Hi --

This started as a question in ruby-talk. It''s about this line of code:

eval(IO.read(init_path), binding, init_path)

This idiom appears in initializer.rb, in v1.2.3, for loading
environment files and plugin init files. (On Edge, the plugin stuff is
moved to another file, but the same idiom''s still used in that file,
and you''ll see it used for the env files in initializer.rb on Edge as
well.)

The question was, why use this idiom instead of load or require?

My assumption is that the answer is this idiom gives you flexible
bindings, but if anyone could verify that, or correct me, I''d totally
appreciate it. I don''t actually see the binding passed being declared
anywhere, so it kind of puzzles me.


Thanks,
Giles


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On 7/27/07, giles bowkett <gilesb@gmail.com>
wrote:
> eval(IO.read(init_path), binding, init_path)
>
> The question was, why use this idiom instead of load or require?
>
> My assumption is that the answer is this idiom gives you flexible
> bindings, but if anyone could verify that, or correct me, I''d
totally
> appreciate it. I don''t actually see the binding passed being
declared
> anywhere, so it kind of puzzles me.
Giles,

You''re on the right track with the binding. Evaling against the
current binding gives (int this case) your environment file access to
the "config" local. Check Kernel#binding in the Ruby core docs for a
bit more enlightenment.


~ j.

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On 7/27/07, giles bowkett <gilesb@gmail.com>
wrote:
>
> Hi --
>
> This started as a question in ruby-talk. It''s about this line of
code:
>
> eval(IO.read(init_path), binding, init_path)
>
> This idiom appears in initializer.rb, in v1.2.3, for loading
> environment files and plugin init files. (On Edge, the plugin stuff is
> moved to another file, but the same idiom''s still used in that
file,
> and you''ll see it used for the env files in initializer.rb on Edge
as
> well.)
>
> The question was, why use this idiom instead of load or require?
>
> My assumption is that the answer is this idiom gives you flexible
> bindings, but if anyone could verify that, or correct me, I''d
totally
> appreciate it. I don''t actually see the binding passed being
declared
> anywhere, so it kind of puzzles me.
I think it''s so some local variables are available in the init.rb
file: directory, lib_path, etc.  Actually, they''re now methods of the
Rails::Plugin class.

-- 
Rick Olson
http://lighthouseapp.com
http://weblog.techno-weenie.net
http://mephistoblog.com

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On 7/27/07, Rick Olson <technoweenie@gmail.com>
wrote:
>
>
> I think it''s so some local variables are available in the init.rb
> file: directory, lib_path, etc.

That was exactly the case. Try to share local variables between files using
load and require to understand why.

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> The question was, why use this idiom instead of load or require?
So that the code gets access to config.*,  using require would be a
different scope.


-- 
Cheers

Koz

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> I think it''s so some local variables are available in the init.rb
> file: directory, lib_path, etc.  Actually, they''re now methods of
the
> Rails::Plugin class.
This suggests that you could refactor it, but you can''t actually
remove it completely, because it''s also used in the code which brings
in environment files.

The code is kinda repetitive:

eval(IO.read(init_path), binding, init_path) # plugins
eval(IO.read(configuration.environment_path), binding,
configuration.environment_path) # env files

So I made a tiny refactoring patch:

http://dev.rubyonrails.org/ticket/9128


Gracias senores,
Giles


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