how to correctly extend form_for / ActionView::Helpers::FormBuilder?

Question

This is similiar to Trying to extend ActionView::Helpers::FormBuilder but I don't want to use :builder => MyThing.

I want to extend form builder to add custom methods. This is the current situation:

module ActsAsTreeHelpers
  def acts_as_tree_block(method, &block)
    yield if block_given?
  end

end


ActionView::Helpers::FormBuilder.send :include, ::ActsAsTreeHelpers

Console:

ruby-1.9.2-p180 :004 > ActionView::Helpers::FormBuilder.included_modules
=> [ActsAsTreeHelpers, ...]

But the following gives me: undefined method acts_as_tree_block for #<ActionView::Helpers::FormBuilder:0xae114dc>

<%= form_for thing do |form| %>
  <%= form.acts_as_tree_block :parent_id, {"test"} %>
<% end %>

What am I missing here?

score 5 · Accepted Answer · edited Jan 14 '12 at 15:40

I also had the same problem. I tried to add a new file named form_builder.rb in folder config/initializers of my project and it works well now.

Below are some contents of my solution. base_helper.rb

def field_container(model, method, options = {}, &block)
  css_classes = options[:class].to_a
  if error_message_on(model, method).present?
    css_classes << 'withError'
  end
  content_tag('p', capture(&block), :class => css_classes.join(' '), :id => "#{model}_#{method}_field")
end

form_builder.rb

class ActionView::Helpers::FormBuilder
  def field_container(method, options = {}, &block)
    @template.field_container(@object_name,method,options,&block)
  end

  def error_message_on(method, options = {})
    @template.error_message_on(@object_name, method, objectify_options(options))
  end
end
ActionView::Base.field_error_proc = Proc.new{ |html_tag, instance| "<span class=\"field_with_errors\">#{html_tag}</span>".html_safe }

_form.html.erb

<%= f.field_container :name do %>
  <%= f.label :name, t("name") %> <span class="required">*</span><br />
  <%= f.text_field :name %>
  <%= f.error_message_on :name %>
<% end %>

Alexis Delahaye · Answer 2 · 2019-05-27T09:21:41.077

The accepted answer no longer worked for me (Rails 5+)

Here is the changes I made to get it to work (Rails 5.2.3) :

# config/initializers/custom_form_builder.rb
class ActionView::Helpers::FormBuilder
  def my_custom_text_field_with_only_letters(method, options = {})
    options[:pattern] = "^[A-Za-z]+$"
    options[:title] = "Only letters please"
    text_field(method, options)
  end

  field_helpers << :my_custom_text_field_with_only_letters
end

field_helpers << :my_custom_text_field_with_only_letters makes sure your new method is available natively in all your application forms.

According to the doc, another possibility is to extend FormBuilder , add your custom method, and then specify in each of your wanted forms which FormBuilder to use :

class MyFormBuilder < ActionView::Helpers::FormBuilder
 def div_radio_button(method, tag_value, options = {})
...

<%= form_for @person, :builder => MyFormBuilder do |f| %>
<%= f.div_radio_button(:admin, "child") %>

how to correctly extend form_for / ActionView::Helpers::FormBuilder?

2 Answers2