Provides a way to use bindings that doesn't require subclassing

mojo/public/cpp/bindings/lib/interface_impl_internal.h

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef MOJO_PUBLIC_CPP_BINDINGS_LIB_INTERFACE_IMPL_INTERNAL_H_
 #define MOJO_PUBLIC_CPP_BINDINGS_LIB_INTERFACE_IMPL_INTERNAL_H_
 
 #include "mojo/public/cpp/bindings/error_handler.h"
+#include "mojo/public/cpp/bindings/interface_binding_delegate.h"
 #include "mojo/public/cpp/bindings/interface_ptr.h"
 #include "mojo/public/cpp/bindings/lib/filter_chain.h"
 #include "mojo/public/cpp/bindings/lib/message_header_validator.h"
 #include "mojo/public/cpp/environment/environment.h"
 #include "mojo/public/cpp/environment/logging.h"
 #include "mojo/public/cpp/system/macros.h"
 
 namespace mojo {
+
+class InterfaceBindingDelegate;
+
 namespace internal {
 
 template <typename Interface>
-class InterfaceImplBase : public Interface {
- public:
-  virtual ~InterfaceImplBase() {}
-  virtual void OnConnectionEstablished() = 0;
-  virtual void OnConnectionError() = 0;
-};
-
-template <typename Interface>
 class InterfaceImplState : public ErrorHandler {
  public:
   typedef typename Interface::Client Client;
 
-  explicit InterfaceImplState(InterfaceImplBase<Interface>* instance)
-      : router_(nullptr),
+  explicit InterfaceImplState(Interface* instance,
+                              InterfaceBindingDelegate* delegate)
+      : delegate_(delegate),
+        router_(nullptr),
         proxy_(nullptr),
-        instance_bound_to_pipe_(false)
-#ifndef NDEBUG
-        ,
-        deleting_instance_due_to_error_(false)
-#endif
-  {
+        instance_bound_to_pipe_(false) {
     MOJO_DCHECK(instance);
     stub_.set_sink(instance);
   }
 
   virtual ~InterfaceImplState() {
-#ifndef NDEBUG
-    MOJO_DCHECK(!instance_bound_to_pipe_ || deleting_instance_due_to_error_);
-#endif
     delete proxy_;
     if (router_) {
       router_->set_error_handler(nullptr);
       delete router_;
     }
   }
 
   void BindProxy(
       InterfacePtr<Interface>* ptr,
       bool instance_bound_to_pipe,
@@ skipping 14 matching lines @@
     filters.Append<typename Interface::Client::ResponseValidator_>();
 
     router_ = new Router(handle.Pass(), filters.Pass(), waiter);
     router_->set_incoming_receiver(&stub_);
     router_->set_error_handler(this);
 
     proxy_ = new typename Client::Proxy_(router_);
 
     instance_bound_to_pipe_ = instance_bound_to_pipe;
 
-    instance()->OnConnectionEstablished();
+    if (delegate_)
+      delegate_->OnConnectionEstablished();
   }
 
   bool WaitForIncomingMethodCall() {
     MOJO_DCHECK(router_);
     return router_->WaitForIncomingMessage();
   }
 
   Router* router() { return router_; }
   Client* client() { return proxy_; }
+  Interface* instance() { return stub_.sink(); }
+
+  bool instance_bound_to_pipe() const { return instance_bound_to_pipe_; }
 
  private:
-  InterfaceImplBase<Interface>* instance() {
-    return static_cast<InterfaceImplBase<Interface>*>(stub_.sink());
-  }
+  virtual void OnConnectionError() override { delegate_->OnConnectionError(); }
 
-  virtual void OnConnectionError() override {
-    // If the the instance is not bound to the pipe, the instance might choose
-    // to delete itself in the OnConnectionError handler, which would in turn
-    // delete this.  Save the error behavior before invoking the error handler
-    // so we can correctly decide what to do.
-    bool bound = instance_bound_to_pipe_;
-    instance()->OnConnectionError();
-    if (!bound)
-      return;
-#ifndef NDEBUG
-    deleting_instance_due_to_error_ = true;
-#endif
-    delete instance();
-  }
-
+  InterfaceBindingDelegate* delegate_;
   Router* router_;
   typename Client::Proxy_* proxy_;
   typename Interface::Stub_ stub_;
   bool instance_bound_to_pipe_;
-#ifndef NDEBUG
-  bool deleting_instance_due_to_error_;
-#endif
 
   MOJO_DISALLOW_COPY_AND_ASSIGN(InterfaceImplState);
 };
 
 }  // namespace internal
 }  // namespace mojo
 
 #endif  // MOJO_PUBLIC_CPP_BINDINGS_LIB_INTERFACE_IMPL_INTERNAL_H_