1 files changed, 10 insertions, 0 deletions
diff --git a/ecs/src/extension.rs b/ecs/src/extension.rs
index e180ac7..9c6614b 100644
--- a/ecs/src/extension.rs
+++ b/ecs/src/extension.rs
@@ -1,6 +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};
@@ -35,6 +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