How to pull a specific field from a Ruby Associations CollectionProxy? - ruby

Question

I have the following models:
class User < ApplicationRecord
has_many :hobbies, dependent: :destroy
end
class Hobby < ApplicationRecord
belongs_to :user
end
I was trying to output to my view the user and its hobbies:
<table>
<tr>
<th>User</th>
<th>Hobby</th>
</tr>
<% #users.each do |u| %>
<tr>
<td><%= u.name %></td>
<td><%= u.hobbies %></td>
</tr>
<% end %>
</table>
But I see the following:
User Hobby
Mad Max <Hobby::ActiveRecord_Associations_CollectionProxy:0x007fa2721ab910>
It looks like I am outputting the collection, but I want the actual hobby name. I have tried u.hobbies.first, u.hobbies[:hobby], etc. I've looked inside http://api.rubyonrails.org/classes/ActiveRecord/Associations/CollectionProxy.html but it's abit confusing for me as a new developer. Can someone tell me how to pull from a specific field from the collection? And which resource out there is a good guide for me to reference in the future?

Answer 1

So this is basically an array of hobbies that gets attached to the user. so you need to iterate over each one and then ask for the attribute you want from it. Try something like this:
<table>
<tr>
<th>User</th>
<th>Hobby</th>
</tr>
<% #users.each do |user| %>
<tr>
<td><%= user.name %></td>
<td>
<% user.hobbies.each do |hobby| %>
<%= hobby.attribute_name %>,
<% end %>
</td>
</tr>
<% end %>
</table>
If you want to get real fancy you could try doing something like this:
<% user.hobbies.each_with_index do |hobby, index| %>
<%= hobby.attribute_name %>
<%= (index == user.hobbies.length-1) ? '' : ','
<% end %>
That is using a ternary operator to basically say only put a comma if the hobby is not the last hobby