Beginner problem with foreign keys

Hi, I’ve been trying to get this to work all night. I’ve made some
progress by reading other posts, but I’m stuck now and can’t figure out
what I am doing wrong.

I have two tables: application_users and user_types. In my
application_users table I have a field named “user_type_id”. At first,
I thought if I set up the foreign key with the correct names, it would
automatically appear in my “new” form, but I got past that issue.

My application_user model looks like this:

class ApplicationUser < ActiveRecord::Base
belongs_to :user_type
validates_presence_of :first_name, :last_name, :user_type_id,
:login_name, :password
end

My user_type model looks like this:

class UserType < ActiveRecord::Base
has_many :application_users
end

In my controller, my new method looks like this:

def new
@application_user = ApplicationUser.new
@user_types = UserType.find_all
end

And I modified the new.rhtml view to contain this select list:

User type
<% @user_types.each do |user_type| %> <%= user_type.user_type %> <% end %>

The select list fills with the data from my user_types table, but when I
submit the form I get the famous “nil object” error under “NoMethodError
in Admin#create”. The extracted source shows my code for the select
list in new.rhtml, specifically the “<% @user_types.each do |user_type|
%>” line.

My create method in my controller looks correct to me:

def create
@application_user = ApplicationUser.new(params[:application_user])
if @application_user.save
flash[:notice] = ‘User was successfully created.’
redirect_to :action => ‘list’
else
render :action => ‘new’
end
end

I figured that there was some problem with my validation and it was
dying when it got sent back to the new form. I commented out the
validation and the form worked correctly. But if I put back the
validation, even just testing the presence of one field, and I don’t
fill out that field, I get the same error.

It’s obvious to me that the problem occurs when the application_user
object can’t be saved, and it gets sent back to the form where the
user_types object is now nil. But I don’t understand why. It seems
that when “application_user.save” fails, it goes to “render :action =>
‘new’” where @user_types should be initialized. The new method works
the first time I hit the form, why does it not work when it is called
from the create method?

Thanks for any help you can give me - this is driving me crazy.

Hi !

2006/4/19, Bill C. [email protected]:

It’s obvious to me that the problem occurs when the application_user
object can’t be saved, and it gets sent back to the form where the
user_types object is now nil. But I don’t understand why. It seems
that when “application_user.save” fails, it goes to “render :action =>
‘new’” where @user_types should be initialized. The new method works
the first time I hit the form, why does it not work when it is called
from the create method?

When you call render :action => :new, this only renders. It doesn’t
execute the logic in the #new method.

To resolve that problem, you have a few solutions:

  1. Add a before_filter that will load @user_types when necessary
  2. Copy/paste the line (big frown from the community)
  3. Make the view find the user types itself (lesser frown)

Hope that helps !

François Beausoleil wrote:

Hi !

When you call render :action => :new, this only renders. It doesn’t
execute the logic in the #new method.

To resolve that problem, you have a few solutions:

  1. Add a before_filter that will load @user_types when necessary
  2. Copy/paste the line (big frown from the community)
  3. Make the view find the user types itself (lesser frown)

Hope that helps !

Thanks a lot. The before_filter is exactly what I was looking for. I
hadn’t gotten that far in the book yet. :wink:

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