basic ECS spawner

addons/gecs/tests/systems/o_test_a.gd

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+## This system runs when an entity that is not dead and has it's transform component changed
+## This is a simple example of a reactive system that updates the entity's transform ONLY when the transform component changes if it's not dead
+class_name TestAObserver
+extends Observer
+
+
+var event_count := 0
+var added_count := 0
+
+
+## The component to watch for changes
+func watch() -> Resource:
+	return C_TestA
+
+
+# What the entity needs to match for the system to run
+func match() -> QueryBuilder:
+	# The query the entity needs to match
+	return ECS.world.query.with_none([C_TestB])
+
+
+# What to do when a property on C_Transform just changed on an entity that matches the query
+func on_component_changed(
+	entity: Entity, component: Resource, property: String, old_value: Variant, new_value: Variant
+) -> void:
+	# Set the transfrom from the component to the entity
+	print("We changed!", entity.name, component.value)
+	event_count += 1
+	
+func on_component_added(entity: Entity, component: Resource) -> void:
+	added_count += 1