WIP: draft internal structure of dependency factory

src/lib/depend.hpp

@@ -44,13 +44,15 @@ namespace lib {
    * Access point to singletons and other kinds of dependencies.
    * Actually this is a Factory object, which is typically placed into a static field
    * of the Singleton (target) class or some otherwise suitable interface.
-   * @note internally uses static fields, so all factory instances share pInstance_
-   * @note there is an ongoing discussion regarding Double Checked Locking pattern,
-   *       which in this case boils down to the question: does \c pthread_mutex_lock/unlock
-   *       constitute a memory barrier, such as to force any memory writes done within
-   *       the singleton ctor to be flushed and visible to other threads when releasing
-   *       the lock? To my understanding, the answer is yes. See
-   *       http://www.opengroup.org/onlinepubs/000095399/basedefs/xbd_chap04.html#tag_04_10
+   * @note uses static fields internally, so all factory instances share pInstance_
+   * @remark there is an ongoing discussion regarding the viability of the
+   *   Double Checked Locking pattern, which requires either the context of a clearly defined
+   *   language memory model (as in Java), or needs to be supplemented by memory barriers.
+   *   In our case, this debate boils down to the question: does \c pthread_mutex_lock/unlock
+   *   constitute a memory barrier, such as to force any memory writes happening \em within
+   *   the singleton ctor to be flushed and visible to other threads when releasing the lock?
+   *   To my understanding, the answer is yes. See
+   *   [posix](http://www.opengroup.org/onlinepubs/000095399/basedefs/xbd_chap04.html#tag_04_10)
    * @param SI the class of the Singleton instance
    * @param Create policy defining how to create/destroy the instance
    * @param Life policy defining how to manage Singleton Lifecycle
@@ -58,9 +60,11 @@ namespace lib {
   template<class SI>
   class Depend
     {
-      typedef lib::ClassLock<SI> ThreadLock;
+      typedef ClassLock<SI> ThreadLock;
+      typedef DependencyFactory<SI> Factory;
       
-      static SI* volatile pInstance_;
+      static SI* volatile instance;
+      static Factory       factory;
       
       
     public:
@@ -72,55 +76,59 @@ namespace lib {
       SI&
       operator() ()
         {
-          if (!pInstance_)
+          if (!instance)
             {
               ThreadLock guard;
               
-              if (!pInstance_)
-                {
-                  if (isDead_)
-                    {
-                      Life<SI>::onDeadReference();
-                      isDead_ = false;
-                    }
-                  pInstance_ = Create<SI>::create();
-                  Life<SI>::scheduleDelete (&destroy);
-            }   }
-          ENSURE (pInstance_);
-          ENSURE (!isDead_);
-          return *pInstance_;
+              if (!instance)
+                instance = factory.buildInstance();
+            }
+          ENSURE (instance);
+          return *instance;
         }
       
-    private:
-      /** @internal helper used to delegate destroying the single instance
-       *  to the Create policy, at the same time allowing the Life policy
-       *  to control the point in the Application lifecycle when the
-       *  destruction of this instance occurs.
-       */
-      static void destroy()
+      void
+      shutdown()
         {
-          REQUIRE (!isDead_);
-          Create<SI>::destroy (pInstance_);
-          pInstance_ = 0;
-          isDead_ = true;
+          ThreadLock guard;
+          
+          factory.deconfigure (instance);
+          instance = NULL;
         }
+      
+      void
+      injectReplacement (SI* mock)
+        {
+          if (mock)
+            {
+              factory.takeOwnership (mock);   // EX_SANE
+              
+              ThreadLock guard;
+              factory.shaddow (instance);
+              instance = mock;
+            }
+          else
+            {
+              factory.discardMock (instance); // EX_FREE
+              
+              ThreadLock guard;
+              instance = factory.restore ();  // EX_SANE
+            }
+        }
+      
+      Depend ();
+      Depend (typename Factory::Constructor ctor);
+      
+    private:
     };
   
   
   // Storage for SingletonFactory's static fields...
   template<class SI>
-    SI* volatile Depend<SI>::pInstance_;
+    SI* volatile Depend<SI>::instance;
   
   
   
-///// Question: can we get rid of the static fields?
-/////       this is tricky because of invoking the destructors. If we rely on instance vars,
-/////       the object may already have been released when the runtime system calls the
-/////       destructors of static objects at shutdown.
-/////       It seems this would either cost us much of the flexibility or get complicated
-/////       to a point where we could as well implement our own Dependency Injection Manager.
-/////       But the whole point of my pervasive use of this singleton template is to remain
-/////       below this borderline of integration ("IoC yes, but avoid DI").
   
 } // namespace lib
 #endif

tests/library/dependency-factory-test.cpp

@@ -87,7 +87,13 @@ namespace test{
       virtual void
       run (Arg)
         {
-          UNIMPLEMENTED ("dependency creation");
+          verify_defaultSingletonCreation();
+          verify_renewal();
+          verify_SubclassCreation();
+          verify_FactoryDefinition_is_sticky();
+          verify_customFactory();
+          verify_temporaryReplacement();
+          verify_automaticReplacement();
         }