Noob Q: How to access a belongs_to object

Sorry for the simplicity on this. I hope this makes for a quick response.

I have two classes:

class UserProfile < ActiveRecord::Base
belongs_to :UserGroup
end

class UserGroup < ActiveRecord::Base

has_many :UserProfiles

end

I want to display the UserGroup.Name for an UserProfile instance.

This snippet returns the correct User_Group id:

@user_profile.User_Group_id

This code seemed the most logical to me:

@user_profile.UserGroup.Name

but I get this error:

You have a nil object when you didn't expect it!
The error occurred while evaluating nil.Name
What should the call be?
Thanks in advance!

FYI, I figured this out. I shouldn't have been using capital letters
in my classes. But now, I've run into a different problem.

These two classes:
class UserProfile < ActiveRecord::Base
  belongs_to :UserGroup
end

class UserGroup < ActiveRecord::Base
  has_many :UserProfiles
end

become:
class UserProfile < ActiveRecord::Base
  belongs_to :usergroup
end

class UserGroup < ActiveRecord::Base
  has_many :userprofiles
end

I'm not getting the error below when I make this call:

<% for user_profile in @user_profiles %>
...
    <td><%=h user_profile.usergroup.Name %></td>
...

========Error======
uninitialized constant UserProfile::Usergroup

Thoughts?

FYI, I figured this out. I shouldn't have been using capital letters
in my classes. But now, I've run into a different problem.

These two classes:
class UserProfile < ActiveRecord::Base
  belongs_to :UserGroup
end

class UserGroup < ActiveRecord::Base
  has_many :UserProfiles
end

become:
class UserProfile < ActiveRecord::Base
  belongs_to :usergroup

Should be 'user_group'

end

class UserGroup < ActiveRecord::Base
  has_many :userprofiles

and 'user_profiles'

Multiple words in the class name correspond to multiple words in the
table and relationship names. Here's another tip to preserve sanity:
Follow the dictionary when deciding whether a name is one word or
multiple words. This rule tells you to call the class 'UserGroup'
and the table 'user_groups' instead of 'Usergroup' and 'usergroups'.