"DataObjects::IntegrityError (ERROR: null value in column violates not-null constraint" error in rails 3

In my model I have

    class Alias
  include DataMapper::Resource


  belongs_to :user


  property :id, String, :key => true, :required => true, :unique => true

  validates_format_of :id, :with => /[0-9a-z\-]/i

end

In my controller:

def new
   @new_alias = @owner.aliases.new()
end
    def create 
         @owner = current_user
         @alias = @owner.aliases.create(params[:alias])
end

And in my view

<%= form_for @new_alias, :url => {:controller => "aliases", :action=>"create"} do |f| %> 
    <%= f.text_field :id, :placeholder => "Account name" %></br>
    <%= f.submit :value => "Create" %>
 <% end %>

For me it looks preatty normal, but when I'm trying to save new alias, it results with with:

ERROR:  null value in column "alias_开发者_高级运维id" violates not-null constraint

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 ~

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&host=localhost&port=5432&username=name&password=pass&database=postgres&path=postgres&schema_search_path=public&encoding=utf8&template=template0)

DataObjects::IntegrityError (ERROR: null value in column "alias_id" violates not-null constraint ):

app/controllers/aliases_controller.rb:5:in `create'

What could be the problem? I'm using rails3, postgres and datamapper.

It appears you have fields in your database that aren't defined in your model, and that some of those fields have not-null constraints on them. Because datamapper only writes the fields it knows about (in this case :id), it does not specify values for any additional fields that might exist in the table. Since the unspecified fields require values, PgSQL is producing an error.

Either remove the not-null constraints, or add those fields to DataMapper with :default values on them.

Not familiar with rails internals, but your column's definition must be so that it allow null values.

I had the same problem with data mapper. This is what I did to fix it:

In Alias class, add an additional line as follows:

property :user_id, Integer

This line defines the foreign key.