Get data attribute value from the Rails form builder without using input field

Question

I have what I hope to be a simple question. I need to display the value for an attribute on the Edit page, while keeping the input field for the same attribute. How might this be accomplished?

Answer 1

Well generally you can just use the original object, like you'll have an @foo that you'll have used in your form_for statement, so you can just use that directly: = @foo.the_attribute

If you're within a partial, or elsewhere where you have only the form builder instance, then you can refer to the underlying object with the .object method, eg.:

= form_for @foo do |f|
  # in here, f.object == @foo

Answer 2

In my case, I'm working with accepts_nested_attributes_for in two models. Event accept nested objects from Speaker . And Speaker has a perfil_id attribute which could be ['Maker', 'Developer', 'Entrepreneur', ...] .

The Speaker 's form is a partial rendered from the principal form, Event 's form:

<%= form_for(event) do |f| %>
    <%= f.text_field :title %>
    <%= f.label :title, 'Event name' %>

    <%= f.fields_for :speakers do |builder| %>
        <%= render 'events/partials/speaker_fields', f: builder %>
    <% end %>

    <%= f.submit %>
<% end %>

Partial

<%= builder.number_field :name %>
<%= builder.label :name %>

<% options = options_from_collection_for_select(@profiles, 'id', 'name', f.object.member_profile_id ) %>
<%= select_tag "event[speakers_attributes][profile_id]", options, prompt: 'Select a Profile' %>

When editing Event's Speakers I wanted a select_tag to select the profile name for the actual Speaker.

I could not use an input field for this. So I need to get the correct values from the builder object and I get what I need by doing this:

f.object.profile_id

Passing it as a fourth param to the select options I get this working:

<% options = options_from_collection_for_select(@profiles, 'id', 'name', f.object.profile_id ) %>

I hope it could be useful for you too!