Rails - Displaying Foreign Key References in a form

Question

I'm doing a simple exercise with two models. Sport and Teams, defined as

rails g scaffold sport name:integer
rails g scaffold team name:integer fans:integer sport:references

(Note: The reason I'm using scaffold is rapidly prototyping so I can learn/experiment with the parts I'm not familiar with yet)

Problem is that my "sport" (i.e. the foreign key reference) is showing like the following

So it's got that weird #<blahl blah> notation to it...

<%= form_for(@team) do |f| %>
  <% if @team.errors.any? %>
    <div id="error_explanation">
      <h2><%= pluralize(@team.errors.count, "error") %> prohibited this team from being saved:</h2>

      <ul>
      <% @team.errors.full_messages.each do |msg| %>
        <li><%= msg %></li>
      <% end %>
      </ul>
    </div>
  <% end %>

  <div class="field">
    <%= f.label :name %><br />
    <%= f.text_field :name %>
  </div>
     <div class="field">
    <%= f.label :fans %><br />
    <%= f.number_field :fans %>
  </div>
  <div class="field">
    <%= f.label :sport %><br />
    <%= f.text_field :sport %>
  </div>
  <div class="actions">
    <%= f.submit %>
  </div>
<% end %>

I've tried changing the one line to @team.sport.name but it results in an error undefined method 'Ice Hockey' for #<Team:0x3e7e040>... Any ideas how to properly display name from here??

Answer 1

You are using a text_field for referencing an existing object, a select with Sports as options would be more appropriate here.

This is where it has to be changed:

<div class="field">
  <%= f.label :sport %><br />
  <%= f.text_field :sport %>
</div>

To:

<div class="field">
  <%= f.label :sport %><br />
  <%= f.select :sport_id, options_for_select(Sport.all.map{|s|[s.name, s.id]}) %>
</div>

The f.select will generate a select box in HTML, the options will me all the sports in your DB.

Some documentation about it:

• http://apidock.com/rails/ActionView/Helpers/FormOptionsHelper/select
• http://guides.rubyonrails.org/form_helpers.html#select-boxes-for-dealing-with-models

A cleaner way would be to set a variable @sports in your controller and call it then in your views:

# in controller
def edit
  @sports = Sport.scoped
  #...

# in edit view
<div class="field">
  <%= f.label :sport %><br />
  <%= f.select :sport_id, options_for_select(@sports.map{ |s| [s.name, s.id] }) %>
</div>

---

Additionnal information: If you want to "pre-select" an option for the select, you have to pass it as the second argument of the options_for_select helper:

options_for_select(@sports.map{ |s| [s.name, s.id] }, params[:sport_id])
# this will select by default the option that matches the value of params[:sport_id]