1 files changed, 17 insertions, 0 deletions
diff --git a/ecs/src/extension.rs b/ecs/src/extension.rs
index 42ebef9..9c6614b 100644
--- a/ecs/src/extension.rs
+++ b/ecs/src/extension.rs
@@ -1,5 +1,7 @@
 use crate::component::Sequence as ComponentSequence;
+use crate::entity::Declaration as EntityDeclaration;
 use crate::sole::Sole;
+use crate::system::observer::Observer;
 use crate::system::System;
 use crate::uid::Uid;
 use crate::{SoleAlreadyExistsError, World};
@@ -34,6 +36,15 @@ impl<'world> Collector<'world>
         self.world.register_system(phase_euid, system);
     }
 
+    /// Adds a observer system to the [`World`].
+    pub fn add_observer<'this, SystemImpl>(
+        &'this mut self,
+        observer: impl Observer<'this, SystemImpl>,
+    )
+    {
+        self.world.register_observer(observer);
+    }
+
     /// Adds a entity to the [`World`].
     pub fn add_entity<Comps>(&mut self, components: Comps)
     where
@@ -42,6 +53,12 @@ impl<'world> Collector<'world>
         self.world.create_entity(components);
     }
 
+    /// Adds a declared entity to the [`World`].
+    pub fn add_declared_entity(&mut self, entity_decl: &EntityDeclaration)
+    {
+        self.world.create_declared_entity(entity_decl);
+    }
+
     /// Adds a globally shared singleton value to the [`World`].
     ///
     /// # Errors