class PEROBS::ObjectBase
Base class for all persistent objects. It provides the functionality common to all classes of persistent objects.
Constants
- NATIVE_CLASSES
Attributes
Public Class Methods
This method generates the destructor for the objects of this class. It is done this way to prevent the Proc object hanging on to a reference to self which would prevent the object from being collected. This internal method is not intended for users to call.
# File lib/perobs/ObjectBase.rb, line 173 def ObjectBase._finalize(store, id, ruby_object_id) proc { store._collect(id, ruby_object_id) } end
New PEROBS
objects must always be created by calling # Store.new()
. PEROBS
users should never call this method or equivalents of derived methods directly. @param p [PEROBS::Handle] PEROBS
handle
# File lib/perobs/ObjectBase.rb, line 148 def initialize(p) _initialize(p) end
Read an raw object with the specified ID from the backing store and instantiate a new object of the specific type.
# File lib/perobs/ObjectBase.rb, line 241 def ObjectBase.read(store, id) # Read the object from database. db_obj = store.db.get_object(id) klass = store.class_map.id_to_class(db_obj['class_id']) # Call the constructor of the specified class. obj = Object.const_get(klass).allocate obj._initialize(Handle.new(store, id)) obj._deserialize(db_obj['data']) obj.restore obj end
Public Instance Methods
Two objects are considered equal if their object IDs are the same.
# File lib/perobs/ObjectBase.rb, line 202 def ==(obj) return false unless obj.is_a?(ObjectBase) obj && @_id == obj._id end
# File lib/perobs/ObjectBase.rb, line 221 def _check_assignment_value(val) if val.respond_to?(:is_poxreference?) # References to other PEROBS::Objects must be handled somewhat # special. if @store != val.store PEROBS.log.fatal 'The referenced object is not part of this store' end elsif val.is_a?(ObjectBase) PEROBS.log.fatal 'A PEROBS::ObjectBase object escaped! ' + 'Have you used self() instead of myself() to get the reference ' + 'of the PEROBS object that you are trying to assign here?' elsif !NATIVE_CLASSES.include?(val.class) PEROBS.log.fatal "Assigning objects of class #{val.class} is not " + "supported. Only PEROBS objects or one of the following classes " + "are supported: #{NATIVE_CLASSES.join(', ')}" end end
This is the real code for initialize. It is called from initialize() but also when we restore objects from the database. In the later case, we don’t call the regular constructors. But this code must be exercised on object creation with new() and on restore from DB. param p [PEROBS::Handle] PEROBS
handle
# File lib/perobs/ObjectBase.rb, line 157 def _initialize(p) @store = p.store @_id = p.id @store._register_in_memory(self, @_id) ObjectSpace.define_finalizer( self, ObjectBase._finalize(@store, @_id, object_id)) @_stash_map = nil # Allocate a proxy object for this object. User code should only operate # on this proxy, never on self. @myself = POXReference.new(@store, @_id) end
Restore the object state from the storage back-end. @param level [Integer] the transaction nesting level
# File lib/perobs/ObjectBase.rb, line 257 def _restore(level) # Find the most recently stored state of this object. This could be on # any previous stash level or in the regular object DB. If the object # was created during the transaction, there is no previous state to # restore to. data = nil if @_stash_map (level - 1).downto(0) do |lvl| break if (data = @_stash_map[lvl]) end end if data # We have a stashed version that we can restore from. _deserialize(data) elsif @store.db.include?(@_id) # We have no stashed version but can restore from the database. db_obj = store.db.get_object(@_id) _deserialize(db_obj['data']) end end
Save the object state for this transaction level to the storage back-end. The object gets a new ID that is stored in @_stash_map to map the stash ID back to the original data.
# File lib/perobs/ObjectBase.rb, line 281 def _stash(level) @_stash_map ||= ::Array.new # Get a new ID to store this version of the object. @_stash_map[level] = _serialize end
Write the object into the backing store database.
# File lib/perobs/ObjectBase.rb, line 208 def _sync # Reset the stash map to ensure that it's reset before the next # transaction is being started. @_stash_map = nil db_obj = { 'class_id' => @store.class_map.class_to_id(self.class.to_s), 'data' => _serialize } @store.db.put_object(db_obj, @_id) end
Library internal method to transfer the Object
to a new store. @param store [Store] New store
# File lib/perobs/ObjectBase.rb, line 179 def _transfer(store) @store = store # Remove the previously defined finalizer as it is attached to the old # store. ObjectSpace.undefine_finalizer(self) # Register the object as in-memory object with the new store. @store._register_in_memory(self, @_id) # Register the finalizer for the new store. ObjectSpace.define_finalizer( self, ObjectBase._finalize(@store, @_id, object_id)) @myself = POXReference.new(@store, @_id) end
This method can be overloaded by derived classes to do some massaging on the data after it has been restored from the database. This could either be some sanity check or code to migrate the object from one version to another. It is also the right place to initialize non-persistent instance variables as initialize() will only be called when objects are created for the first time.
# File lib/perobs/ObjectBase.rb, line 198 def restore end