Relations - return relation from indexer as ref

friflo · Feb 2, 2025 · fec110b · fec110b
1 parent ce59360
commit fec110b
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Showing 2 changed files with 50 additions and 3 deletions.
diff --git a/src/ECS/Relations/Relations.cs b/src/ECS/Relations/Relations.cs
@@ -2,6 +2,7 @@
 // See LICENSE file in the project root for full license information.
 
 
+using System;
 using System.Collections;
 using System.Collections.Generic;
 using System.Diagnostics.CodeAnalysis;
@@ -85,8 +86,19 @@ public string Debug()
     /// Return the relation at the given <paramref name="index"/>.<br/>
     /// Executes in O(1).
     /// </summary>
-    public TRelation this[int index] => components[positions != null ? positions[index] : position];
-
+    public ref TRelation this[int index] {
+        get {
+            if (index >= 0 && index < Length) {
+                return ref components[positions != null ? positions[index] : position];
+            }
+            throw IndexOutOfRangeException(index);
+        }
+    }
+
+    private IndexOutOfRangeException IndexOutOfRangeException(int index) {
+        return new IndexOutOfRangeException($"index: {index} Length: {Length}");
+    }
+
     // --- IEnumerable<>
     IEnumerator<TRelation>   IEnumerable<TRelation>.GetEnumerator() => new RelationsEnumerator<TRelation>(this);
 

diff --git a/src/Tests/ECS/Relations/Test_Relations.cs b/src/Tests/ECS/Relations/Test_Relations.cs
@@ -124,7 +124,42 @@ public static void Test_Relations_add_remove_default()
         IsFalse (entity.RemoveRelation<AttackRelation>(default));
         relations = entity.GetRelations<AttackRelation>();
         AreEqual("{ }", relations.Debug());
-    }    
+    }
+
+    [Test]
+    public static void Test_Relations_modify_relations()
+    {
+        var store   = new EntityStore();
+        var target1 = store.CreateEntity();
+        var target2 = store.CreateEntity();
+        var entity  = store.CreateEntity();
+        var relations = entity.GetRelations<AttackRelation>();
+        Throws<IndexOutOfRangeException>(() => {
+            _ = relations[0];
+        });
+        // --- add first relation
+        IsTrue  (entity.AddRelation(new AttackRelation { target = target1, speed = 1 }));
+        relations = entity.GetRelations<AttackRelation>();
+        AreEqual("{ 1 }", relations.Debug());
+        relations[0].speed = 11;
+        AreEqual(11, entity.GetRelation<AttackRelation, Entity>(target1).speed);
+        var e = Throws<IndexOutOfRangeException>(() => {
+            _ = relations[1];
+        });
+        AreEqual("index: 1 Length: 1", e!.Message);
+
+        // --- add second relation
+        IsTrue  (entity.AddRelation(new AttackRelation { target = target2, speed = 2 }));
+        relations = entity.GetRelations<AttackRelation>();
+        AreEqual("{ 1, 2 }", relations.Debug());
+        relations[0].speed = 21;
+        relations[1].speed = 22;
+        AreEqual(21, entity.GetRelation<AttackRelation, Entity>(target1).speed);
+        AreEqual(22, entity.GetRelation<AttackRelation, Entity>(target2).speed);
+        Throws<IndexOutOfRangeException>(() => {
+            _ = relations[2];
+        });
+    }
 
 #pragma warning disable CS0618 // Type or member is obsolete
     [Test]