title: "DataObjects::IntegrityError (ERROR: null value in column violates not-null constraint" error in rails 3
body: <p>In my model I have</p>
  
  <pre><code>    class Alias
    include DataMapper::Resource
  
  
    belongs_to :user
  
  
    property :id, String, :key =&gt; true, :required =&gt; true, :unique =&gt; true
  
    validates_format_of :id, :with =&gt; /[0-9a-z\-]/i
  </code></pre>
  
  <p>end</p>
  
  <p>In my controller:</p>
  
  <pre><code>def new
     @new_alias = @owner.aliases.new()
  end
      def create 
           @owner = current_user
           @alias = @owner.aliases.create(params[:alias])
  end
  </code></pre>
  
  <p>And in my view</p>
  
  <pre><code>&lt;%= form_for @new_alias, :url =&gt; {:controller =&gt; "aliases", :action=&gt;"create"} do |f| %&gt; 
      &lt;%= f.text_field :id, :placeholder =&gt; "Account name" %&gt;&lt;/br&gt;
      &lt;%= f.submit :value =&gt; "Create" %&gt;
   &lt;% end %&gt;
  </code></pre>
  
  <p>For me it looks preatty normal, but when I'm trying to save new alias, it results with with:</p>
  
  <pre><code>ERROR:  null value in column "alias_id" violates not-null constraint
  </code></pre>
  
  <blockquote>
    <p>Processing by AliasesController#create
    as HTML   Parameters: {"utf8"=>"✓",
    "authenticity_token"=>"/token=",
    "alias"=>{"id"=>"IDNAME"},
    "commit"=>"Create"}  ~   SQL (0.632ms)
    SELECT "id", "encrypted_password",
    "remember_created_at",
    "reset_password_token",
    "reset_password_sent_at",
    "failed_attempts", "unlock_token",
    "locked_at", "sign_in_count",
    "current_sign_in_at",
    "last_sign_in_at",
    "current_sign_in_ip",
    "last_sign_in_ip", "username",
    "email", "name", "country" FROM
    "users" WHERE "id" IN (2) LIMIT 1  ~<br>
    SQL (0.491ms)  SELECT "id" FROM
    "aliases" WHERE "id" = 'IDNAME' ORDER
    BY "id" LIMIT 1 Completed   in 11ms  ~
    SQL (0.531ms)  INSERT INTO "aliases"
    ("id", "user_id") VALUES ('IDNAME', 2)
    ~ ERROR:  null value in column
    "alias_id" violates not-null
    constraint  (code: 33575106, sql
    state: 23502, query: INSERT INTO
    "aliases" ("id", "user_id") VALUES
    ('IDNAME', 2), uri:
    postgres:name@localhost:5432postgres?adapter=postgres&amp;host=localhost&amp;port=5432&amp;username=name&amp;password=pass&amp;database=postgres&amp;path=postgres&amp;schema_search_path=public&amp;encoding=utf8&amp;template=template0)</p>
    
    <p>DataObjects::IntegrityError (ERROR: 
    null value in column "alias_id"
    violates not-null constraint ):<br>
    app/controllers/aliases_controller.rb:5:in
    `create'</p>
  </blockquote>
  
  <p>What could be the problem? I'm using rails3, postgres and datamapper. </p>