Question

Our application uses a number of environments so we can experiment with settings without breaking things. In a typical controller action, I have something like this:

def some_action    
  ...
  if @foo.development_mode == 'Production'           
    @settings = SomeHelper::Production.lan(bar)
  elsif @foo.development_mode == 'Beta'
    @settings = SomeHelper::Beta.lan(nas)
  elsif @foo.development_mode == 'Experimental'
    @settings = SomeHelper::Experimental.lan(nas)
  end
  ...
 end

Since we have dozens of these, I figured I could try and dry things up with something like this:

 @settings = "SomeHelper::#{@foo.development_mode}.lan(bar)"

Which obviously doesn’t work – I just get:

 "NasHelper::Production.lan(bar)"

How can I reduce this down or do I have to stick with what I’ve got??

Answer 1

If your concern is that you’re ending up with a String rather than the object, you can use String.constantize (Rails only, with standard Ruby you’d have to implement this; it uses Object.const_get(String))

Another option would be .const_get (e.g. Object.const_get(x) where x is your string), you it doesn’t, on its own, nest correctly, so you would have to split at “::”, etc.

Also, there’s the option of using eval to evaluate the String.
But note: eval should be used with great care (it’s powerful), or not at all.

Edit:

This means that instead of:

 @settings = "SomeHelper::#{@foo.development_mode}.lan(bar)"

You could run:

 @settings = "SomeHelper::#{@foo.development_mode}".constantize.lan(bar)

Useful Sources:

http://api.rubyonrails.org/classes/ActiveSupport/Inflector.html#method-i-constantize

http://www.ruby-forum.com/topic/183112

http://blog.grayproductions.net/articles/eval_isnt_quite_pure_evil