Forms to create and update Mongoid array fields

Question

I've been struggling to create a form for a Mongoid model that has an array field. I want my form to have on text box per entry in the array. If I'm creating a new record, the default will be one empty field (and some javascript to add new fields dynamically on the page).

I've searched around for a solution using fields_for but it seems that is more intended to handle the case where you have an array of objects/models and not the case I have, which is an array of strings.

I'm going to use the example of a person and a phone number.

class Person
  include Mongoid::Document
  field :name, :type => String
  field :phone_numbers, :type => Array
end

For the controller, just assume the typical controller but in the new method I initialized the phone_number array with one blank string.

Here's the form code:

  <%= form_for(@person) do |f| %>
    <div class="field">
      <%= f.label :name %><br />
      <%= f.text_field :name %>
    </div>
    <div class="field">
      <%= f.label :phone_numbers %><br />
      <% @person.phone_numbers.each do |phone_number| %>
        <%= text_field_tag "person[phone_numbers][]", phone_number %>
      <% end %>
    </div>
  <% end %>

This all works fine. There are a few things that I don't like.

• The hardcoded name of the field in the text_field_tag call.
• Using text_field_tag instead of f.text_field
• Having the feeling like I should somehow be using fields_for instead of this

Does anybody have any better suggestions on how to implement this? Or would you consider this correct?

Answer 1

I agree with your concerns -

1. The hard-coded name of the field in the text_field_tag call.

2. Using text_field_tag instead of f.text_field

3. using fields_for

After doing some research found that first two concerns can be solved and probably also third can but haven't tried yet.

 <%= form_for(@person) do |f| %>
  <div class="field">
    <%= f.label :name %><br />
    <%= f.text_field :name %>
  </div>
  <div class="field">
    <%= f.label :phone_numbers %><br />
    <% @person.phone_numbers.each do |phone_number| %>
      <%= f.text_field :phone_numbers, :name => "#{f.object_name}[phone_numbers][]"%>
    <% end %>
  </div>
<%end%>

Another clean approach could be having form builder defined text_field and then having -

def text_field(attribute, *args)
  args.last.merge!(:name => "#{object_name}[#{attribute}][]") if args.last && args.last.is_a?(Hash) && args.last.delete(:array)
  super(attribute, args)
end

<% @person.phone_numbers.each do |phone_number| %>
  <%= f.text_field :phone_numbers, :array => true%>
<% end %>

You can find more information here

Answer 2

You could work with embeds_many:

class Person
  include Mongoid::Document
  field :name
  embeds_many :phone_numbers
end

class PhoneNumber
  include Mongoid::Document
  field :number
  embedded_in :person
end

And then, within your view, you could use:

<%= form_for(@person) do |f| %>
  <div class="field">
    <%= f.label :name %><br />
    <%= f.text_field :name %>
  </div>
  <%= @person.phone_numbers.each do |phone_number| %>
    <%= f.fields_for phone_number do |p| %>
      <div class="field">
        <%= p.label :number %><br />
        <%= p.text_field :number %>
      </div>
    <% end %>
  <% end %>
<% end %>

Answer 3

According to a comment posted mosch in a comment to his own solution:

whenever you use fields_for, it expects an object with accessors for the attributes and some other methods like new_record? Basically speaking, the object hat to implement the ActiveModel interface.

The answer to my question is that there is not a better way unless I create another model for the phone nubmers, like was mosch suggested.

Answer 4

The second div should be like the following

<div class="field"><%= f.fields_for :phone_numbers do | phone | %>
 <%= phone.text_field "phone_numer[]" %><% end %></div>