From b02261bd25a5fc307dd6b9f8fd0a87fb2d3d91f1 Mon Sep 17 00:00:00 2001
From: David Wicks <wicks.db@gmail.com>
Date: Mon, 2 Sep 2013 16:04:51 -0400
Subject: Added remove<C>() method for removal of components by type.

Along with this, there is a ComponentRemovedEvent<T> that is
delivered whenever a component is removed from an entity.
---
 entityx/Entity.h       | 35 +++++++++++++++++++++++++++++++++++
 entityx/Entity_test.cc | 20 ++++++++++++++++++++
 2 files changed, 55 insertions(+)

diff --git a/entityx/Entity.h b/entityx/Entity.h
index 8eee892..09cff22 100644
--- a/entityx/Entity.h
+++ b/entityx/Entity.h
@@ -113,6 +113,9 @@ public:
   template <typename C, typename ... Args>
   entityx::shared_ptr<C> assign(Args && ... args);
 
+  template <typename C>
+  entityx::shared_ptr<C> remove();
+
   template <typename C>
   entityx::shared_ptr<C> component();
 
@@ -220,6 +223,17 @@ struct ComponentAddedEvent : public Event<ComponentAddedEvent<T>> {
   entityx::shared_ptr<T> component;
 };
 
+/**
+ * Emitted when any component is removed from an entity.
+ */
+template <typename T>
+struct ComponentRemovedEvent : public Event<ComponentRemovedEvent<T>> {
+  ComponentRemovedEvent(Entity entity, entityx::shared_ptr<T> component) :
+      entity(entity), component(component) {}
+
+  Entity entity;
+  entityx::shared_ptr<T> component;
+};
 
 /**
  * Manages Entity::Id creation and component assignment.
@@ -442,6 +456,21 @@ class EntityManager : public entityx::enable_shared_from_this<EntityManager>, bo
     return assign<C>(entity, entityx::make_shared<C>(args ...));
   }
 
+  /**
+   * Remove a Component from an Entity::Id
+   *
+   * Emits a ComponentRemovedEvent<C> event.
+   */
+  template <typename C>
+  entityx::shared_ptr<C> remove(Entity::Id id) {
+    entityx::shared_ptr<C> component = entityx::static_pointer_cast<C>(entity_components_.at(C::family()).at(id.index()));
+    entity_components_.at(C::family()).at(id.index()).reset();
+    entity_component_mask_.at(id.index()) &= ~(uint64_t(1) << C::family());
+    if (component)
+      event_manager_->emit<ComponentRemovedEvent<C>>(Entity(shared_from_this(), id), component);
+    return component;
+  }
+
   /**
    * Retrieve a Component assigned to an Entity::Id.
    *
@@ -592,6 +621,12 @@ entityx::shared_ptr<C> Entity::assign(Args && ... args) {
   return manager_.lock()->assign<C>(id_, args ...);
 }
 
+template <typename C>
+entityx::shared_ptr<C> Entity::remove(){
+  assert(valid() && component<C>());
+  return manager_.lock()->remove<C>(id_);
+}
+
 template <typename C>
 entityx::shared_ptr<C> Entity::component() {
   assert(valid());
diff --git a/entityx/Entity_test.cc b/entityx/Entity_test.cc
index b779873..e207ade 100644
--- a/entityx/Entity_test.cc
+++ b/entityx/Entity_test.cc
@@ -335,6 +335,26 @@ TEST_F(EntityManagerTest, TestComponentAddedEvent) {
   ASSERT_EQ(10, receiver.direction_events);
 }
 
+TEST_F(EntityManagerTest, TestComponentRemovedEvent) {
+  struct ComponentRemovedReceiver : public Receiver<ComponentRemovedReceiver> {
+    void receive(const ComponentRemovedEvent<Direction> &event) {
+      removed = event.component;
+    }
+
+    entityx::shared_ptr<Direction> removed;
+  };
+
+  ComponentRemovedReceiver receiver;
+  ev->subscribe<ComponentRemovedEvent<Direction>>(receiver);
+
+  ASSERT_FALSE(receiver.removed);
+  Entity e = em->create();
+  e.assign<Direction>(1.0, 2.0);
+  auto p = e.remove<Direction>();
+  ASSERT_EQ(receiver.removed, p);
+  ASSERT_FALSE(e.component<Direction>());
+}
+
 TEST_F(EntityManagerTest, TestEntityAssignment) {
   Entity a, b;
   a = em->create();
-- 
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