class Entity:
# Keep track of the latest ID for entities to ensure they get unique IDs.
_id_counter = 0
def __init__(self, system_manager):
# Fairly certain we don't need this to be a dict, as
# we are unlikely to want to reference specific
# systems by id.
self._systems = []
# A dict of all components inside this entity.
# The keys are the IDs of the components.
self._components = {}
# The components this entity has.
self._component_bitstring = BitString()
# Keep track of the old bitstring so we can see
# what has changed when we call refresh twice.
self._old_component_bitstring = BitString()
# Systems that this entity belongs to.
self._systems_bitstring = BitString()
# Ensure unique IDs.
self.ID = Entity._id_counter
Entity._id_counter = Entity._id_counter + 1
# The system manager the entity belongs to.
# Gives access to the existing systems.
self.system_manager = system_manager
# Remove an entity from all systems it is hooked into.
def kill(self):
for system in self._systems:
system._remove_entity(self)
# Allow all systems to hook into (or out of) the entity.
def refresh(self):
# If the entity is already hooked in remove them, so we don't add them twice.
# This design can be optimized, but low priority since we likely only refresh
# an entity once.
if not self._old_component_bitstring.is_empty():
self.kill()
self._old_component_bitstring = self._component_bitstring
for system in self.system_manager._systems:
# Add the entity if it maps correctly to the system.
does_map = True
for component_id in system._component_list:
if not self._component_bitstring.contains(component_id):
does_map = False
if does_map:
system._add_entity(self)
self._systems.append(system)
# Return a component that the entity contains based on the class.
def get_component(self, component_class):
try:
return self._components[component_class.ID]
except:
return None
# Add a component to the entity. Be sure to refresh afterwards.
def add_component(self, component):
# Fairly certain we don't want two PositionComponents for example.
if component.__class__.ID in self._components:
raise Exception(component.__class__.__name__ + " already inside of entity!")
self._components[component.__class__.ID] = component
#self._components.append(component)
self._component_bitstring.add_to_set(component.ID)
