Rails Helpers and Instance Variables

November 10th, 2005

I was reading the code for the FileColumn, helper and I had a thought. What if we could obviate the need for requiring instance variables for helpers ?

A recent example on the mailing list ? render partial and passing in the object, by Mark Van Holstyn. In the thread, he asks why he can’t do:

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def edit
  @user = User.find_by_id(1)
  render :partial => 'address', :object => @user.address}
end
His partial being: 


<%= text_area('address', 'street') %>
Reading FileColumn helper’s code, and the code in Rails own helpers, the following idiom is used to get a hold of the instance variable: 
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def url_for_file_column(object_name, method, suffix=nil)
  object = instance_variable_get("@#{object_name.to_s}")
  ...
end

What if we did it this way instead ?

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def url_for_file_column(object_name, method, suffix=nil)
  object =  case object_name
            when String, Symbol
              instance_variable_get("@#{object_name.to_s}")
            else
              object_name
            end
  ...
end

Actually, this should all be abstracted away in some kind of helper for helpers. Let me take a moment to prepare a patch. I think this would make things quite a bit easier for partial users.

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I am François Beausoleil, a Ruby on Rails coder. During the day, I work on XLsuite. At night, I am interested many things. Read my biography

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