Added state event.

src/dawn/state/StateOwner.hpp

@@ -4,7 +4,7 @@
 // https://opensource.org/licenses/MIT
 
 #pragma once
-#include "assert/assert.hpp"
+#include "StateEvent.hpp"
 
 namespace Dawn {
   template<class V>
@@ -12,15 +12,10 @@ namespace Dawn {
 
   class StateOwner {
     private:
-      std::map<void*, std::vector<std::function<void()>>> effects;
+      std::map<void*, std::vector<std::function<void()>>> effectListeners;
+      std::vector<std::function<void()>> stateUpdateListeners;
 
     public:
-      /**
-       * Invoked event listener for the subclass that listens for all changes
-       * to any part of this state updated.
-       */
-      virtual void onStateUpdate() = 0;
-
       /**
        * Creates a new state property and listens for its change.
        * 
@@ -46,7 +41,32 @@ namespace Dawn {
        */
       template<class V>
       void useEffect(StateProperty<V> &property, const std::function<void()> &fn) {
-        this->effects[(void*)&property].push_back(fn);
+        assertFalse(property.owner == this);
+        this->effectListeners[(void*)&property].push_back(fn);
+      }
+
+      /**
+       * Listen for changes to any single state property managed by this state
+       * owner.
+       * 
+       * @param fn Function to be invoked when any state property is updated.
+       */
+      void useStateUpdated(const std::function<void()> &fn) {
+        this->stateUpdateListeners.push_back(fn);
+      }
+
+      /**
+       * Listen for when an event is invoked by a state event. This is intended
+       * to allow for cross-state-owner communication in a simple and effective
+       * way.
+       * 
+       * @tparam A The arguments from the state event that are calledback.
+       * @param event The event that is being subscribed to.
+       * @param fn The function to be inokved on event trigger.
+       */
+      template<typename...A>
+      void useEvent(StateEvent<A...> &event, const std::function<void(A...)> &fn) {
+        event.listeners.push_back(fn);
       }
 
       /**
@@ -60,14 +80,19 @@ namespace Dawn {
        */
       template<class V>
       void _statePropertyUpdated(StateProperty<V> *prop, V n, V o) {
-        this->onStateUpdate();
-
-        auto eff = &this->effects[prop];
+        auto eff = &this->effectListeners[prop];
+        
         auto itEff = eff->begin();
         while(itEff != eff->end()) {
           (*itEff)();
           ++itEff;
         }
+
+        auto itUpdate = this->stateUpdateListeners.begin();
+        while(itUpdate != this->stateUpdateListeners.end()) {
+          (*itUpdate)();
+          ++itUpdate;
+        }
       }
 
       /**
@@ -79,7 +104,11 @@ namespace Dawn {
        */
       template<class V>
       void _statePropertyDestroyed(StateProperty<V> *prop) {
-        this->effects.erase((void*)prop);
+        this->effectListeners.erase((void*)prop);
+      }
+
+      virtual ~StateOwner() {
+        
       }
   };
 }