Question

I can’t find how to display a dynamic label in Rails, i’ve tried using the :value => show_name property but it didn’t work, it only displays Show name. Here is the view code

<p>
   <div class="control-group">
           <%= f.label :show_name, :value => :show_name, :class => 'control-label' %> 
           <%= #this next line fails with undefined method `show_name' for #<ActionView::Helpers::FormBuiler>
              #f.label f.send :show_name, :class => 'control-label'
           %> 
       <div class="controls">
           <%= f.text_field :variable_value, :class => 'text_field' %> 
           <%= f.hidden_field :variable_id, :class => 'text_field' %> 
       <%= f.hidden_field :show_name, :class => 'text_field' %> 
       </div>
   </div>
<p>

and if needed here is the show_name definition inside my model.

  def show_name
    Variable.find_by_id(self.variable_id).name
  end

Answer 1

Ok, so i end up finding a solution that is very DRY, thank to this post. And the only thing im going to do is explain a lit bit more what to do:

First we are going to asume the most complex case in which we have nested forms and so we are using fields_for inside a form_for method:

  <!-- f represents the form from `form_for` -->
  <%= f.fields_for :nested_model do |builder| %>
    <p>
      <div class="control-group">

         <!-- here we are just calling a helper method to get things DRY -->

         <%= builder.label return_value_of_symbol(builder,:show_name), :class => 'control-label' %> 
         <div class="controls">
            <%= builder.text_field :variable_value, :class => 'text_field' %> 
            <%= builder.hidden_field :variable_id, :class => 'text_field' %> 
         </div>
      </div>
    </p>
  <% end %>

Note that we included the builder object(as specified in the fields_for call) in the parameters of our helper.

In our helper we define the return_value_of_symbol function

  def return_value_of_symbol(obj,sym)
    # And here is the magic, we need to call the object method of fields_for
    # to obtain the reference of the object we are building for, then call the
    # send function so we send a message with the actual value of the symbol 
    # and so we return that message to our view.  
    obj.object.send(sym)
  end