Autoloading objects â? Ruby equivalent for PHP5 "__autoload

naum · July 24, 2006, 11:58am

Does there exist a Ruby equivalent to PHP5 “magic” __autoload method
that spares the developer from detailing a list of “require” statements?
http://us2.php.net/autoload

Or is this something that a homebrewed solution is necessary? Like
catching the exception and testing for file existence, etc.â?¦ or is there
a gem/extension featuring this functionality?

naum · July 24, 2006, 1:50pm

check out module Kernel - RDoc Documentation its
close
to what you want.
ActiveSupport is a gem which does autoloading, but it may be specific in
the
way it does it.

j`ey
http://www.eachmapinject.com

naum · July 24, 2006, 2:22pm

Naum T. wrote:

Does there exist a Ruby equivalent to PHP5 “magic” __autoload method
that spares the developer from detailing a list of “require” statements?
PHP: Autoloading Classes - Manual

Or is this something that a homebrewed solution is necessary? Like
catching the exception and testing for file existence, etc.â?¦ or is there
a gem/extension featuring this functionality?

Sure there is ;D

Kernel#autoload:
http://ruby-doc.org/core/classes/Kernel.html#M002963

and:

Module#autoload:
http://ruby-doc.org/core/classes/Module.html#M001061

lopex

naum · July 24, 2006, 2:40pm

On Jul 24, 2006, at 5:58 AM, Naum T. wrote:

Does there exist a Ruby equivalent to PHP5 “magic” __autoload method
that spares the developer from detailing a list of “require”
statements?
PHP: Autoloading Classes - Manual

Or is this something that a homebrewed solution is necessary? Like
catching the exception and testing for file existence, etc.? or is
there
a gem/extension featuring this functionality?

const_missing is a little more like PHP’s __autoload function.

The following, for example will attempt to just do: require in the event it can’t find the class.

def Object.const_missing name
require name.to_s.downcase
const_get(name)
end

I’ve never used it though, so anyone can feel free to correct me for
any gotchas that I’m not aware of.
-Mat

naum · July 24, 2006, 2:51pm

Marcin MielÅ¼yÅ?ski wrote:

Sure there is ;D

Kernel#autoload:
module Kernel - RDoc Documentation

and:

Module#autoload:
class Module - RDoc Documentation
That’s not quite it. You need to call Module.autoload yourself. PHP’s
autoload is called by the interpreter to perform the inclusion. You
could use const_missing to get a similar functionality, though…

def Object.const_missing(name)
load name.to_lower + “.rb”
end

That’s got a few rough edges, though, to put it mildly…

naum · July 24, 2006, 2:57pm

Alex Y. wrote:

def Object.const_missing(name)
load name.to_lower + “.rb”
end

That’s got a few rough edges, though, to put it mildly…

I mean, besides the fact that it won’t work, unlike Mat’s. Should have
tested that one…

naum · July 24, 2006, 5:55pm

You would probably want to use some metaprogramming to define
const_missing recursively on currently defined constants, and then
it’s pretty much the same as PHP’s __autoload().

naum · July 24, 2006, 5:45pm

That’s seems to be the ticket.

Knew about ruby autoload, but you have to specify up front each
module/file whereis PHP5, it’s (but named “__autoload”) a “catch all”.

One solution is to glob the directory (where I have my classes stored)
and issue autoload for each result:

assumes my custom classes begin with upper case

Dir.glob(’[A-Z]*.rb’).each do |f|
rsym = f.gsub("[.]rb$", ‘’)
autoload(:#{rsym}, f)
end

const_missing is a little more like PHP’s __autoload function.

The following, for example will attempt to just do: require in the event it can’t find the class.

def Object.const_missing name
require name.to_s.downcase
const_get(name)
end

I’ve never used it though, so anyone can feel free to correct me for
any gotchas that I’m not aware of.
-Mat

naum · July 25, 2006, 3:02pm

On Jul 25, 2006, at 7:22 AM, Gonzalo G. wrote:

def Object.const_missing elem
require elem.to_s
end

a = A.new

PS. I would advise NOT doing this kind of thing, thou. It can make
your code much harder to debug for other developers.

you need

def Object.const_missing elem
require elem.to_s
const_get(elem)
end

To make this work, otherwise the ‘A’ in A.new becomes the return
value of ‘require elem.to_s’
-Mat

naum · July 25, 2006, 1:23pm

Naum T. escribiÃ³:

Does there exist a Ruby equivalent to PHP5 “magic” __autoload method
that spares the developer from detailing a list of “require” statements?
PHP: Autoloading Classes - Manual

Or is this something that a homebrewed solution is necessary? Like
catching the exception and testing for file existence, etc.â?¦ or is there
a gem/extension featuring this functionality?

def Object.const_missing elem
require elem.to_s
end

a = A.new

PS. I would advise NOT doing this kind of thing, thou. It can make
your code much harder to debug for other developers.

naum · July 25, 2006, 3:18pm

I do hope you know that there’s a lot of things in Ruby that makes a
developer’s debugging life quite hard, but the point is that it’s
convenient to have these sort of solutions.

naum · March 20, 2007, 5:19pm

Mat S. wrote:

const_missing is a little more like PHP’s __autoload function.

The following, for example will attempt to just do: require in the event it can’t find the class.

def Object.const_missing name
require name.to_s.downcase
const_get(name)
end

Well, th const_missing sollution does work, but only in scripts called
directly in shell by ‘ruby’ executable. When using it in script called
in browser i get:

[Tue Mar 20 16:56:49 2007] [error] mod_ruby: error in ruby
[Tue Mar 20 16:56:49 2007] [error] mod_ruby:
/home/services/httpd/html/TRON/ruby/index.rb:11: uninitialized constant
#Module:0xb6a6ea30::Test (NameError)
[Tue Mar 20 16:56:49 2007] [error] mod_ruby: from
/usr/lib/ruby/1.8/apache/ruby-run.rb:38:in load' [Tue Mar 20 16:56:49 2007] [error] mod_ruby: from /usr/lib/ruby/1.8/apache/ruby-run.rb:38:inhandler’

Got apache 2.2 with mod_ruby configured as follows:

LoadModule ruby_module modules/mod_ruby.so

    AddType text/html .rb

    RubyRequire apache/ruby-run

    <Files *.rb>
            Options +ExecCGI
            SetHandler ruby-object
            RubyHandler Apache::RubyRun.instance
    </Files>

What i`ve been trying to get is an equivalent of PHP __autoload()
routine working under both shell execution and apache handler. Know any?

naum · March 21, 2007, 1:10am

On 3/20/07, Piotr B. [email protected] wrote:

end
/usr/lib/ruby/1.8/apache/ruby-run.rb:38:in `load’

What i`ve been trying to get is an equivalent of PHP __autoload()
routine working under both shell execution and apache handler. Know any?

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