CODEWITHSUNDEEP
ruby-on-railsruby
Derek Thurn
Derek Thurn

Reputation: 15365

Ruby: Locate class definition at run time?

I'm having an odd probably with rails right now... a class is being defined somewhere, and I can't find it. Grepping for "class ClassName" hasn't managed to locate it, but it's definitely there when I load up the rails console. It's just a vanilla class inheriting from Object with nothing else defined... quite boring. So, what I'd like is a way to figure out where this class constant was originally defined from the rails console. Something to print out the value of '__ FILE __' when this class was declared, in other words. I feel like some type of metaprogramming should make this possible.

I thought of just doing

ClassName.class_exec { __FILE__ }

But this just always gives me the current file.

Upvotes: 3

Views: 1330

Answers (1)

Wayne Conrad
Wayne Conrad

Reputation: 107999

The hook method inherited, if defined, gets called whenever a subclass is created. Therefore:

#!/usr/bin/ruby1.8

class Object
  def self.inherited(child)
    target_class = "Child"
    raise "#{target_class} defined" if child.name == target_class
  end
end

class Parent
end

class Child < Parent    # => /tmp/foo.rb:6:in `inherited': Child defined (RuntimeError)
                        # =>         from /tmp/foo.rb:13

end

Upvotes: 5

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