refactor(ecs): replace optional components with Option query term

1 files changed, 40 insertions, 2 deletions

diff --git a/ecs/src/query/term.rs b/ecs/src/query/term.rs
index ce453f0..78668c5 100644
--- a/ecs/src/query/term.rs
+++ b/ecs/src/query/term.rs
@@ -1,7 +1,13 @@
+use std::any::type_name;
 use std::marker::PhantomData;
 
-use crate::component::Component;
-use crate::query::{TermWithoutField, TermsBuilder, TermsBuilderInterface};
+use crate::component::{Component, HandleFromEntityComponentRef, Ref as ComponentRef};
+use crate::query::{
+    TermWithField,
+    TermWithoutField,
+    TermsBuilder,
+    TermsBuilderInterface,
+};
 
 pub struct With<ComponentT>
 where
@@ -40,3 +46,35 @@ where
         terms_builder.without::<ComponentT>();
     }
 }
+
+impl<ComponentRefT> TermWithField for Option<ComponentRefT>
+where
+    ComponentRefT: ComponentRef,
+{
+    type Field<'a> = Option<ComponentRefT::Handle<'a>>;
+
+    fn apply_to_terms_builder<const MAX_TERM_CNT: usize>(
+        _terms_builder: &mut TermsBuilder<MAX_TERM_CNT>,
+    )
+    {
+    }
+
+    fn get_field<'world>(
+        entity_handle: &crate::entity::Handle<'world>,
+        world: &'world crate::World,
+    ) -> Self::Field<'world>
+    {
+        Some(
+            ComponentRefT::Handle::<'world>::from_entity_component_ref(
+                Some(entity_handle.get_component(ComponentRefT::Component::id())?),
+                world,
+            )
+            .unwrap_or_else(|err| {
+                panic!(
+                    "Creating handle to component {} failed: {err}",
+                    type_name::<ComponentRefT::Component>()
+                );
+            }),
+        )
+    }
+}