Add trait for easy registration with the World

src/world/mod.rs

@@ -501,6 +501,14 @@ impl World {
             }
         }
     }
+
+    /// Adds the given bundle of resources/components.
+    pub fn add_bundle<B>(&mut self, bundle: B)
+    where
+        B: Bundle,
+    {
+        bundle.add_to_world(self);
+    }
 }
 
 unsafe impl Send for World {}
@@ -529,3 +537,9 @@ impl Default for World {
         }
     }
 }
+
+/// Trait used to bundle up resources/components for easy registration with `World`.
+pub trait Bundle {
+    /// Add resources/components to `world`.
+    fn add_to_world(self, world: &mut World);
+}

src/world/tests.rs

@@ -101,3 +101,23 @@ fn delete_twice() {
     world.delete_entity(e).unwrap();
     assert!(world.entities().delete(e).is_err());
 }
+
+#[test]
+fn test_bundle() {
+    let mut world = World::new();
+
+    pub struct SomeResource {
+        pub v: u32,
+    }
+
+    pub struct TestBundle;
+
+    impl Bundle for TestBundle {
+        fn add_to_world(self, world: &mut World) {
+            world.add_resource(SomeResource { v: 12 });
+        }
+    }
+
+    world.add_bundle(TestBundle);
+    assert_eq!(12, world.read_resource::<SomeResource>().v);
+}