collection_select validation problem

I'm trying to assign a parent foreign key value using
collection_select from my child "new" form. The problem I'm having is
if I do not make a selection, I get the following error instead of the
Rails validates_presence_of error:

You have a nil object when you didn't expect it!
You might have expected an instance of Array.
The error occurred while evaluating nil.map

If I make a selection, everything works just fine. What do I need to
do to get the Rails validationvalidates_presence_of error?

Here's the code:

MODEL

class Client < ActiveRecord::Base
  has_many :programs
  validates_presence_of :eid, :name
end

class Program < ActiveRecord::Base
  belongs_to :client
  validates_presence_of :client_id
  validates_associated :client
end

CONTROLLERS

def new
    @program = Program.new
    @clients = Client.find(:all, :order=>"name")

    respond_to do |format|
      format.html # new.html.erb
      format.xml { render :xml => @program }
    end
  end

def create
    @program = Program.new(params[:program])

    respond_to do |format|
      if @program.save
        flash[:notice] = 'Program was successfully created.'
        format.html { redirect_to(@program) }
        format.xml { render :xml => @program, :status
=> :created, :location => @program }
      else
        format.html { render :action => "new" }
        format.xml { render :xml => @program.errors, :status
=> :unprocessable_entity }
      end
    end
  end

VIIEW

<%=
    collection_select('program',
                      'client_id',
                      @clients,
                      :id,
                      :name,
                      { :include_blank => true }
                      )
   %>

Thx for the assistance!

Still stumped on this. If I replace the collection_select with a
text_field, the validates_presence_of :client_id
fires when I attempt to save the Program without a client_id. BUT
when I use collection_select, and do not make a selection before
attempting to to save the Program, I get the the nil object error. Why
doesn't the validate_presence_of: client_id catch this?? I can see in
the request that the client_id is an empty. Shouldn't that cause
validates_precence_of to fail?

Can anyone explain to me what I'm doing wrong here?

Thanks,
Jeff

{"commit"=>"Create",
"authenticity_token"=>"4bec56fa77ee992dc0e3e13d169bf310ee7351ff",
"program"=>{"eid"=>"",
"name"=>"",
"end_dt(1i)"=>"2007",
"end_dt(2i)"=>"12",
"end_dt(3i)"=>"23",
"client_id"=>"",
"url"=>"",
"start_dt(1i)"=>"2007",
"end_dt(4i)"=>"13",
"start_dt(2i)"=>"12",
"end_dt(5i)"=>"45",
"start_dt(3i)"=>"23",
"start_dt(4i)"=>"13",
"start_dt(5i)"=>"45"}}

I'm trying to assign a parent foreign key value using
collection_select from my child "new" form. The problem I'm having is
if I do not make a selection, I get the following error instead of the
Rails validates_presence_of error:

You have a nil object when you didn't expect it!
You might have expected an instance of Array.
The error occurred while evaluating nil.map

If I make a selection, everything works just fine. What do I need to
do to get the Rails validationvalidates_presence_of error?

Well if you encounter a validation error and render the 'new'
template. That template requires a @clients instance variable that you
are setting up in the new action but not in the create action.

Fred

Thank you Fred!

Problem solved by adding @clients = Client.find(:all, :order=>"name")
to my Create method. I was not considering that errors from Create
needed to be redisplayed and collection_select is part of that form
that is redisplayed and it expects a @clients instance variable.

Appreciate the help.

Jeff