Question

I have a project instance with a nested task. If i debug project.task i got what i expect:

# debug result
--- !ruby/object:Task
attributes:
  id: 1
  name: XYZ

If i want to debug project.task.name i got the error message “undefined method `name’ for nil:NilClass”.

# this works
<% @projects.each do |project| %>
    <%= project.name %><br/>
    <%= debug project.task %>
<% end %>        


# this does not work
<% @projects.each do |project| %>
    <%= project.name %><br/>
    <%= debug project.task.name %>
<% end %>        

Answer 1

The first one works because if you execute :

project.task

and there is a project but there is no task, you get nil.

However, when you execute :

project.task.name

You get an exception if task is nil, since it cannot find the name attribute. However, you can force it to return nil if a task is not there, by using the rails try method :

project.task.try(:name)