mojo/application/public/cpp/lazy_interface_ptr.h

   1 // Copyright 2014 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #ifndef MOJO_APPLICATION_PUBLIC_CPP_LAZY_INTERFACE_PTR_H_
   6 #define MOJO_APPLICATION_PUBLIC_CPP_LAZY_INTERFACE_PTR_H_
   7
   8 #include "mojo/application/public/cpp/connect.h"
   9 #include "mojo/application/public/interfaces/service_provider.mojom.h"
  10
  11 namespace mojo {
  12
  13 // An InterfacePtr that will request an implementation from a specified
  14 // ServiceProvider when it is first accessed with the get() method.
  15 template <typename Interface>
  16 class LazyInterfacePtr : public InterfacePtr<Interface> {
  17  public:
  18   LazyInterfacePtr() : service_provider_(nullptr) {}
  19
  20   explicit LazyInterfacePtr(ServiceProvider* service_provider)
  21       : service_provider_(service_provider) {}
  22
  23   void set_service_provider(ServiceProvider* service_provider) {
  24     if (service_provider != service_provider_) {
  25       InterfacePtr<Interface>::reset();
  26     }
  27     service_provider_ = service_provider;
  28   }
  29
  30   Interface* get() const {
  31     if (!InterfacePtr<Interface>::get() && service_provider_) {
  32       mojo::ConnectToService<Interface>(
  33           service_provider_, const_cast<LazyInterfacePtr<Interface>*>(this));
  34     }
  35     return InterfacePtr<Interface>::get();
  36   }
  37   Interface* operator->() const { return get(); }
  38   Interface& operator*() const { return *get(); }
  39
  40  private:
  41   ServiceProvider* service_provider_;
  42 };
  43
  44 }  // namespace mojo
  45
  46 #endif  // MOJO_APPLICATION_PUBLIC_CPP_LAZY_INTERFACE_PTR_H_