implement runtime type GetComponent

encompass-cs/ComponentMessageManager.cs

@@ -249,6 +249,18 @@ namespace Encompass
             }
         }
 
+        internal (Guid, IComponent) ReadExistingComponentByEntityAndType(Entity entity, Type type)
+        {
+            if (entityToTypeToExistingComponentID.ContainsKey(entity) && entityToTypeToExistingComponentID[entity].TryGetValue(type, out Guid id))
+            {
+                return (id, componentIDToComponent[id]);
+            }
+            else
+            {
+                throw new NoComponentOfTypeOnEntityException("No Component of type {0} exists on Entity {1}", type.Name, entity.ID);
+            }
+        }
+
         internal (Guid, TComponent) ReadPendingComponentByEntityAndType<TComponent>(Entity entity) where TComponent : struct, IComponent
         {
             if (entityToTypeToPendingComponentID.ContainsKey(entity) && entityToTypeToPendingComponentID[entity].TryGetValue(typeof(TComponent), out Guid id))
@@ -261,6 +273,18 @@ namespace Encompass
             }
         }
 
+        internal (Guid, IComponent) ReadPendingComponentByEntityAndType(Entity entity, Type type)
+        {
+            if (entityToTypeToPendingComponentID.ContainsKey(entity) && entityToTypeToPendingComponentID[entity].TryGetValue(type, out Guid id))
+            {
+                return (id, componentIDToComponent[id]);
+            }
+            else
+            {
+                throw new NoComponentOfTypeOnEntityException("No Component of type {0} exists on Entity {1}", type.Name, entity.ID);
+            }
+        }
+
         // check if entity has component of type
 
         internal bool HasExistingOrPendingComponent<TComponent>(Entity entity) where TComponent : struct, IComponent

encompass-cs/Engine.cs

@@ -333,6 +333,52 @@ namespace Encompass
             }
         }
 
+        /// <summary>
+        /// Returns a Component with the specified Type that exists on the Entity.
+        /// </summary>
+        /// <exception cref="Encompass.Exceptions.NoComponentOfTypeOnEntityException">
+        /// Thrown when the Entity does not have a Component of the specified Type
+        /// </exception>
+        /// <exception cref="Encompass.Exceptions.IllegalReadException">
+        /// Thrown when the Engine does not declare that it reads the given Component Type.
+        /// </exception>
+        protected (Guid, IComponent) GetComponent(Entity entity, Type type)
+        {
+            var pending = typeof(PendingComponentMessage<>).MakeGenericType(type);
+            var existing = typeof(ComponentMessage<>).MakeGenericType(type);
+
+            var pendingRead = receiveTypes.Contains(pending);
+            var existingRead = receiveTypes.Contains(existing);
+
+            if (existingRead && pendingRead)
+            {
+                if (componentMessageManager.HasPendingComponent(entity, pending))
+                {
+                    return componentMessageManager.ReadPendingComponentByEntityAndType(entity, pending);
+                }
+                else if (componentMessageManager.HasExistingComponent(entity, existing))
+                {
+                    return componentMessageManager.ReadExistingComponentByEntityAndType(entity, existing);
+                }
+                else
+                {
+                    throw new NoComponentOfTypeOnEntityException("No Component of type {0} exists on Entity {1}", type.Name, entity.ID);
+                }
+            }
+            else if (existingRead)
+            {
+                return componentMessageManager.ReadExistingComponentByEntityAndType(entity, existing);
+            }
+            else if (pendingRead)
+            {
+                return componentMessageManager.ReadPendingComponentByEntityAndType(entity, pending);
+            }
+            else
+            {
+                throw new IllegalReadException("Engine {0} tried to read undeclared Component {1}", GetType().Name, type.Name);
+            }
+        }
+
         /// <summary>
         /// Returns true if the Entity has a Component of the given Type.
         /// </summary>

test/ComponentTest.cs

@@ -271,6 +271,44 @@ namespace Tests
             Assert.AreEqual((componentID, mockComponent), gottenMockComponentIDPair);
         }
 
+        [Receives(typeof(EntityMessage))]
+        [Reads(typeof(MockComponent))]
+        class GetMockComponentByRuntimeType : Engine
+        {
+            public override void Update(double dt)
+            {
+                foreach (var entityMessage in ReadMessages<EntityMessage>())
+                {
+                    gottenMockComponentIDPair = ((Guid, MockComponent))GetComponent(entityMessage.entity, typeof(MockComponent));
+                }
+            }
+        }
+
+        [Test]
+        public void GetComponentByRuntimeType()
+        {
+            var worldBuilder = new WorldBuilder();
+            worldBuilder.AddEngine(new GetMockComponentEngine());
+
+            var entity = worldBuilder.CreateEntity();
+
+            MockComponent mockComponent;
+            mockComponent.myInt = 3;
+            mockComponent.myString = "hello";
+
+            var componentID = worldBuilder.SetComponent<MockComponent>(entity, mockComponent);
+
+            EntityMessage entityMessage;
+            entityMessage.entity = entity;
+            worldBuilder.SendMessage(entityMessage);
+
+            var world = worldBuilder.Build();
+
+            world.Update(0.01);
+
+            Assert.AreEqual((componentID, mockComponent), gottenMockComponentIDPair);
+        }
+
         struct HasComponentTestMessage : IMessage
         {
             public Entity entity;