I frequently have to use methods such as 'radio_button' and 'check_box_tag' when I don't have an object with a method that will automatically determine the value of the input field. Therefore, I have to check to see if a certain parameter has been passed, and if so, if the parameter's value matches that of the input's value. This method does that.

It's designed to be used in a Rails helper. You can either pass it the object, method, and value (the same parameters as, for example, radio_button) or name and value (the same parameters as radio_button_tag).

   1  def checked?( *args )
   2    if args.length == 3
   3      object, method, value = args
   4      if params[object] && params[object][method] && params[object][method] == value
   5        'checked'
   6      end
   7    elsif args.length == 2
   8      name, value = args
   9      if params[name] && params[name] == value
  10        true
  11      end
  12    end
  13  end

Here's an example usage:

   1  <%= radio_button 'person', 'age', '12', :checked => checked?( 'person', 'age', '12' ) %>

If params[:person][:age] exists and it equals '12', then 'checked?' returns 'checked'; otherwise, it returns nil.