From: Rick DeNatale <rick.denatale@...>
Date: 2007-04-03T10:03:50+09:00
Subject: Re: Find the fully qualified name of a class from a string

On 3/31/07, Nasir Khan <rubylearner@gmail.com> wrote:
> Here is an abridged (out of context) version of my original solution. (which
> I am using now)
> -----
> nasir@sparkle:misc>cat find_class_name.rb
>
> module EmptyModule
>    def EmptyModule.clear_all
>     constants.each {|x| remove_const(x.to_sym)}
>    end
> end
>
> @my_classes = []
>
> def class_from_string(str)
>   EmptyModule.clear_all  # clean the slate
>   EmptyModule.module_eval(str)
> end
>
> cstr = <<EOF
> module B
>   class A
>     def a
>       puts "hello"
>     end
>   end
> end
> module B
>   class C
>   end
>   class D
>   end
> end
> EOF
>
> # This string will usually come from some external invocation of this
> function
>
> class_from_string(cstr)
>
>
> def find_class mod
>   mod.constants.each do |str|
>     m = mod.const_get(str)
>     if m.class == Module
>       find_class(m)
>     else
>       cname = m.to_s
>       cname = cname.match(/EmptyModule::/).post_match
>       @my_classes << cname
>     end
>   end
> end
>
>
> find_class( EmptyModule )
> puts @my_classes.uniq
>
> ---------------
>
> And the result -
>
> nasir@sparkle:misc>ruby find_class_name.rb
> B::D
> B::C
> B::A
>
> ----------------
>
> I guess I will stick with this solution. set_trace_func usage is very
> interesting but as I could have potentially several such evaluations going
> on in parallel, I would go with the solution above.
>
> Comments criticisms welcome.

This is still not thread safe since if you are doing this on two
different threads they are sharing the EmptyModule.

Here's my variation using your approach but with an anonymous module
to do the module_eval:

rick@frodo:/public/rubyscripts$ cat find_classes2.rb
class String
  def all_class_names
    mod = Module.new
    mod.module_eval(self)
    mod.all_class_names
  end
end

class Module
  def all_class_names
    class_names = []
    constants.each do |const_name|
      const = const_get(const_name)
      case const
      when Class
        class_names << const.to_s.split(/::/,2)[1]
      when Module
        class_names += const.all_class_names
      end
    end
    class_names.uniq
  end
end

cstr = <<EOF
module B
  class A
    def a
      puts "hello"
    end
  end
end

module B
  class C
  end
  class D
  end

  NonClassConst = :non_class_const
end
EOF

puts cstr.all_class_names
rick@frodo:/public/rubyscripts$ ruby find_classes2.rb
B::C
B::A
B::D



-- 
Rick DeNatale

My blog on Ruby
http://talklikeaduck.denhaven2.com/