From: Kalman Noel <invalid@...>
Date: 2006-09-23T22:55:12+09:00
Subject: Re: How do I instantiate a class who's name is dynamic?

Marcin Miel��y��ski:
> dblack@wobblini.net wrote:
>>   class Object
>>     def const_get_recursive(const)
>>       const.split("::").inject(Object) {|c1,c2| c1.const_get(c2)}
>>     end
>>   end
>
> I know that eval is not save but it appears that it is much faster than 
> inject version
> 
> class A
>      class B
>         C = "foo"
>      end
> end

You may speed your method up a little by avoiding blocks with multiple
arguments, as following. Still eval is fastest, though, of course, nobody will
recommend it.

class Object
  def const_get_eaching(const)
    c = Object
    const.split('::').each { |x| c = c.const_get x }
    c
  end
end


n=10000
Benchmark.bm do |x|
     x.report("eval")   { n.times{ eval("A::B::C") }}
     x.report("inject") { n.times{ Object.const_get_recursive("A::B::C") }}
     x.report("each")   { n.times{ Object.const_get_eaching("A::B::C") }}

end

# Results:

        user     system      total        real
eval    0.100000   0.000000   0.100000 (  0.101864)
inject  0.210000   0.040000   0.250000 (  0.258335)
each    0.160000   0.030000   0.190000 (  0.184249)

Kalman