Custom form helpers

Question

Is there a way that I can create a custom form helper so that instead of:

special_field_tag :object, :method

I can achieve something like:

form.special_field :method

Answer 1

Yes, you can add to the FormBuilder class and get access to the object passed into the form_for. I've done this for a lot of things: dates, times, measurements, etc. Heres an example:

class ActionView::Helpers::FormBuilder
  include ActionView::Helpers::TagHelper
  include ActionView::Helpers::FormTagHelper
  include ActionView::Helpers::FormOptionsHelper
  include ActionView::Helpers::CaptureHelper
  include ActionView::Helpers::AssetTagHelper

  # Accepts an int and displays a smiley based on >, <, or = 0
  def smile_tag(method, options = {})
    value = @object.nil? ? 0 : @object.send(method).to_i
    options[:id] = field_id(method,options[:index])
    smiley = ":-|"
    if value > 0
      smiley = ":-)"
    elsif smiley < 0
       smiley = ":-("
    end
    return text_field_tag(field_name(method,options[:index]),options) + smiley
  end

  def field_name(label,index=nil)
    output = index ? "[#{index}]" : ''
    return @object_name + output + "[#{label}]"
  end

  def field_id(label,index=nil)
    output = index ? "_#{index}" : ''
    return @object_name + output + "_#{label}"
  end

end

Which you can use like this:

<% form_for @quiz do |f| %>
  <%= f.smile_tag(:score) %>
<% end %>

There are some instance variables created by Rails that you can access in these helper methods:

• @object - the model object specified by the form
• @object_name - the class name of the object
• @template - I think its an instance of the ActionView, you can possibly bypass all the includes I added by calling methods on the template. Haven't tried that yet.
• @options - options passed to the FormBuilder when its created by the form_for call

I wrote the field_id and field_name methods to create these attributes on the HTML input elements the same way the regular helpers do, I'm sure there is a way to tie into the same methods that Rails uses, but I haven't found it yet.

The sky is the limit on what you can do with these helper methods, they simply return strings. You can create entire HTML tables or pages in one, but you better have a good reason to.

This file should be added in the app/helpers folder