Rails form with multiple nested models causes issues with radio groups

actionview, radio-button, ruby-on-rails

Solution

You must give each order item a unique index when you call fields_for. If you're calling fields_for in this manner, you need to keep track of the index of the array you pass to fields_for. Rails can do this for you by using nested forms.

The solution is to use nested forms.

<%form_for :order do |f|%>
  Form stuff for this particular order.
  If @order.order_items is empty you may need to build one before the next line.
  <%f.fields_for :order_items do |oi_f| %>
    Form stuff for this particular order_item (prefixed with oi_f.)
    <%Colour.all.each do |colour| %>
      <%=oi_f.radio_tag(:colour_id, colour.id)%>
    <%end%>
  <%end%>
<%end%>

Looks like you're posting to the orders_controller so this should be a drop in replacement.

Problem

I'm having a problem with nested model forms that contain radio buttons, when I have multiple models all the radio buttons are treated as being in the same group. My model contains a has_many relationship like this: ``` class Order < ActiveRecord::Base has_many :order_items accepts_nested_attributes_for :order_items end Class OrderItem < ActiveRecord::Base belongs_to :order end ``` I then have a partial that creates the `OrderItem` model form using ``` <% fields_for "order[order_items_attributes][]", order_item do |f| %> ``` And contained within this form is a group of radio buttons created inside a for loop with ``` radio_button_tag "order[order_items_attributes][][colour_id]", "#{colour.id}" ``` This works fine when there is only one child, however as soon as I insert multiple children all the radio buttons belong to the same group as they all have the same attribute `name="order[order_items_attributes][][colour_id]"`. This is all on a new model form so I can't use array indexes (`name="order[order_items_attributes][0][colour_id]"`) as Rails gives the error `expected Hash (got Array) for param 'order_items_attributes'` I was wrong about that last part, error was because I was mixing indexed and non-indexed name attributes. Adding index values was the key to solving this. Here is the contents of the `params[:order]` hash when only one nested model is present: ``` {"order_items_attributes"=> [{"size"=>"Small", "colour_id"=>"4"], "first_name"=>"sdf", "last_name"=>"sdf", "email"=>"sdfg@sgf.com"} ``` And when two nested models are present: ``` {"order_items_attributes"=> [{"size"=>"Small", "colour_id"=>"4"}, {"size"=>"Small"}], "first_name"=>"sdf", "last_name"=>"sdf", "email"=>"sdfg@sgf.com"} ``` As you can see only the first `order_item` has it's colour_id attribute. This occurs regardless of which model the selected radio button belonged to (which makes sense). How can I render the radio buttons such that it creates a separate group for each child model?

Original source