rails 4, change default form builder globally

Question

I have sub-classed the default form builder to add some additional methods. Sample code is below.

module ApplicationHelper
    class AppFormBuilder < ActionView::Helpers::FormBuilder
        def coordinates_field(method, options = {})
            options[:readonly] = 'true'
            ....
            @template.text_field(@object_name, method, objectify_options(options))
        end
    end
end

This works well, but to use it I have to change the view code for every form that uses the coordinates_field method, i.e.,

<%= form_for @object, :builder => ApplicationHelper::AppFormBuilder do |f| %>
...
<% end %>

It sounds like it is theoretically possible to change the default form builder globally (config.action_view.default_form_builder), but I can't seem to get this to work. This is what I have tried in /config/application.rb:

module Web
  class Application < Rails::Application
    ...
    config.action_view.default_form_builder = "ApplicationHelper::AppFormBuilder"
  end
end

Which results in error undefined method 'new' for "ApplicationHelper::AppFormBuilder":String when I hit a view that has a form.

If I instead try this

config.action_view.default_form_builder = ApplicationHelper::AppFormBuilder

I get the error *config.action_view.default_form_builder = ApplicationHelper::AppFormBuilder* when the application starts.

Can anyone provide guidance on how to get this to work?

Answer 1

As mentioned in the official docs, in Rails 5 the correct way is to specify it in a controller. To make it application wide, just set in your ApplicationController:

class ApplicationController < ActionController::Base
  default_form_builder AppFormBuilder
end

This makes much more sense. FormHelpers are part of the view layer and not the application config.

Answer 2

ApplicationHelper::AppFormBuilder is not required yet at the time application.rb loads. You can try to put this in a separate initializer file (create one in config\initializers):

module Web
  class Application
    ActionView::Base.default_form_builder = AppFormBuilder
  end
end