#--
# WontoMedia - a wontology web application
# Copyright (C) 2011 - Glen E. Ivey
# www.wontology.com
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU Affero General Public License version
# 3 as published by the Free Software Foundation.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU Affero General Public License for more details.
#
# You should have received a copy of the GNU Affero General Public License
# along with this program in the file COPYING and/or LICENSE. If not,
# see <http://www.gnu.org/licenses/>.
#++
# Model for the representation of "items" (things that can be related
# to each other through "connections") in WontoMedia's database. The
# schema listing the data fields for an Item is, of course, in
# db/schema.rb. And Rails' automatically-provided model methods are
# based on the field names there.
#
# WontoMedia uses Rails' "single-table inheritance" to create several
# specialized types of Item objects, all of which are stored in the
# same database table together. The type of object a particular table
# row represents is determined by that object's <tt>sti_type</tt>
# field. There are a number of constants and methods in the module
# ItemHelper that can be used load or evaluate +sti_type+ and to
# perform generic operations on Item instances that correctly preserve
# their child class.
#
# A great deal of this model's behavior is provided through Rails
# validation methods (<tt>validates_...</tt>), see the source for
# details.
class Item < ActiveRecord::Base
# This constant is a bit mask for Item.flags. A non-zero value
# indicates that the Item instance should not be user-modifiable.
DATA_IS_UNALTERABLE = 1
# support sub-classes for Individual, Category, Property, Qualified
self.inheritance_column = "sti_type"
# name
validates_presence_of :name, :message => "Item's name cannot be blank."
validates_length_of :name, :maximum => 80,
:message => "Item name must be 80 characters or less."
validates_each :name do |record, attr, value|
if !(value =~ /^[a-zA-Z][a-zA-Z0-9._:-]*$/m) ||
(value =~ /\n/m)
record.errors.add attr, "must start with a letter, and can contain only"\
"letters, numbers, and/or the period, colon, dash, and underscore."
end
end
validates_uniqueness_of :name, :message =>
"There is already a item with the same name."
# title
validates_presence_of :title, :message => "Item's title cannot be blank."
validates_length_of :title, :maximum => 255,
:message => "Item title must be 255 characters or less."
validates_each :title do |record, attr, value|
if value =~ /[\n\t]/m
record.errors.add attr, "should not be multiple lines."
end
end
validates_length_of :description, :maximum => 65000,
:allow_nil => true, :allow_blank => true,
:message => "Item description must be 65,000 characters or less."
# This method is a hack to provide a legitimate default value for
# the +flags+ field of an Item that hasn't been initialized yet.
# Alternative at http://blog.phusion.nl/2008/10/03/47/
def flags #:nodoc:
# Note that the default value returned here must/does match the
# column default specified in the database schema
self[:flags] or 0
end
@class_item = nil
@class_has_been_set = false
after_save :after_save_callback # update class-defining connection after
# main object saves; rollback still works
def class_item
if @class_has_been_set
@class_item # ignore db content if this has been set
# explicitly. This will eventually be
# saved or discarded
else
iio_item = Item.find_by_name('is_instance_of')
class_assignment = Connection.first( :conditions => [
"subject_id = ? AND predicate_id = ?", id, iio_item.id ] )
if class_assignment.nil? or
class_assignment.kind_of_obj != Connection::OBJECT_KIND_ITEM
return nil
else
return class_assignment.obj
end
end
end
def class_item_id
item = class_item
return item.nil? ? nil : item.id
end
def class_item=( new_class_item )
@class_item = new_class_item
@class_has_been_set = true
end
def class_item_id=( new_class_id )
@class_item = new_class_id.nil? ? nil : Item.find_by_id( new_class_id )
@class_has_been_set = true
end
def is_class?
return( !( Connection.first( :conditions => [
"predicate_id = ? AND obj_id = ?",
Item.find_by_name('is_instance_of').id,
id ] ).nil? ) or
!( Connection.first( :conditions => [
"predicate_id = ? AND (subject_id = ? OR obj_id = ?)",
Item.find_by_name('sub_class_of').id,
id, id ] ).nil? )
)
end
def superclass_of
defining_connection = Connection.first( :conditions => [
"subject_id = ? AND predicate_id = ?",
id, Item.find_by_name('sub_class_of').id ] )
return defining_connection.obj unless defining_connection.nil?
return nil
end
def instance_of
connection = Connection.first( :conditions => [
"subject_id = ? AND predicate_id = ?",
id, Item.find_by_name('is_instance_of').id ] )
return nil if connection == nil
return connection.obj
end
private
def after_save_callback
if @class_has_been_set
iio_item = Item.find_by_name('is_instance_of')
class_assignment = Connection.first( :conditions => [
"subject_id = ? AND predicate_id = ?", id, iio_item.id ] )
if class_assignment && @class_item == class_assignment.obj
return true # class-defining connection already in db -> done
end
if class_assignment # if we're here, current db is different
class_assignment.destroy # so get rid of it
end
begin
class_assignment = Connection.new( {
:subject_id => id,
:predicate_id => iio_item.id,
:obj_id => @class_item.id,
:kind_of_obj => Connection::OBJECT_KIND_ITEM } )
@class_has_been_set = false
return class_assignment.save
rescue
return false
end
end
return true
end
end