Basic ActiveModel methods not working on objects - ruby-on-rails

Question

I asked a question earlier about calling associated model attributes.
Specifically, I asked about trying to display the names of the Vip model instances associated with an event.
Initially I had
<% #organization.events.each do |event| %>
<p>
<table>
<tr>
<td>
<%= event.name %>
</td>
<td>
<%= event.vips.name %>
</td>
</tr>
</table>
</p>
<% end %>
Which I changed to
<%= event.vips.first.name %>
and it worked for a little while. I eventually adjusted it to
<% event.vips.each do |vip| %>
<%= vip.name %>
which also worked for a little while. But when I came back to the computer after taking a break, new event form submissions were no longer displaying the vip's name on the organization show page, even though the database was being updated with the vip_id foreign key.
In fact, when I tried
<%= event.vips.first.name %>
again, I got an error saying "undefined method `name' for nil:NilClass"
I'm really not sure what changed, or what I'm doing wrong. So any help would be appreciated.
Update:
To help clarify the problem, I get the following outputs from the console:
irb(main):005:0> Event.first
Event Load (0.2ms) SELECT "events".* FROM "events" ORDER BY "events"."id" ASC LIMIT 1
=> #<Event id: 1, when: "2015-08-25 00:00:00", organization_id: 1, created_at: "2015-08-25 04:47:43", updated_at: "2015-08-25 04:47:43", name: "John's Event", vip_id: 1>
irb(main):006:0> Vip.first
Vip Load (0.2ms) SELECT "vips".* FROM "vips" ORDER BY "vips"."id" ASC LIMIT 1
=> #<Vip id: 1, name: "John", created_at: "2015-08-25 04:46:23", updated_at: "2015-08-25 04:46:23", organization_id: 1, event_id: nil>
irb(main):007:0> #organization
=> #<Organization id: 1, name: "Test Org", created_at: "2015-08-25 04:46:03", updated_at: "2015-08-25 04:46:03", user_id: 1>
irb(main):008:0> #organization.events.first
=> #<Event id: 1, when: "2015-08-25 00:00:00", organization_id: 1, created_at: "2015-08-25 04:47:43", updated_at: "2015-08-25 04:47:43", name: "John's Event", vip_id: 1>
irb(main):009:0> #organization.events.first.vips
Vip Load (0.2ms) SELECT "vips".* FROM "vips" WHERE "vips"."event_id" = ? [["event_id", 1]]
=> #<ActiveRecord::Associations::CollectionProxy []>
irb(main):010:0>

Answer 1

Your event has no vips. Since event.vips is basically an empty array, calling #first on it returns nil. You then try to call #name on nil. But #name isn't a method of nil, hence the error undefined method 'name' for nil:NilClass.

Answer 2

Normally,
event.vips.first.name will return the error you received if event.vips.first is Nil (which just means that that specific event has no vips, because .first returned Nil or nothing).
In some other times however event.vips.first is a Vip record (which just means that that specific event has at least one Vip).
Since in my first Scenario it returned nil, then nil.name will obviously return an error. However, in my second scenario that it retuned vip, then vip.name will now work as you were expecting it to be.
You may try this if you want to disregard the error being raised: event.vips.first.try(:name)

Answer 3

Your code will work if update the event_id of vip
Vip.first.update_attribute event_id, Event.first.id
Issue happen because we don't have an association between Event.first and Vip.first
btw, I don't think we should use event.vips.first.name because vips can be empty
We can change it a little, ex:
event.vips.first.try(:name)
or
event.vips.map(&:name).join(", ")