Generate node interfaces' getters and traits. (#1069)

Signed-off-by: Michel Hidalgo <michel@ekumenlabs.com>
Co-authored-by: Karsten Knese <karsten@openrobotics.org>

rclcpp/CMakeLists.txt

@@ -101,19 +101,65 @@ configure_file(
   COPYONLY
 )
 # generate header with logging macros
-set(python_code
+set(python_code_logging
   "import em"
   "em.invoke(['-o', 'include/rclcpp/logging.hpp', '${CMAKE_CURRENT_SOURCE_DIR}/resource/logging.hpp.em'])")
-string(REPLACE ";" "$<SEMICOLON>" python_code "${python_code}")
+string(REPLACE ";" "$<SEMICOLON>" python_code_logging "${python_code_logging}")
 add_custom_command(OUTPUT include/rclcpp/logging.hpp
   COMMAND ${CMAKE_COMMAND} -E make_directory "include/rclcpp"
-  COMMAND ${PYTHON_EXECUTABLE} ARGS -c "${python_code}"
+  COMMAND ${PYTHON_EXECUTABLE} ARGS -c "${python_code_logging}"
   DEPENDS "${CMAKE_CURRENT_BINARY_DIR}/logging.hpp.em.watch"
   COMMENT "Expanding logging.hpp.em"
   VERBATIM
 )
 list(APPEND ${PROJECT_NAME}_SRCS
   include/rclcpp/logging.hpp)
+
+file(GLOB interface_files "include/rclcpp/node_interfaces/node_*_interface.hpp")
+foreach(interface_file ${interface_files})
+  get_filename_component(interface_name ${interface_file} NAME_WE)
+
+  # "watch" template for changes
+  configure_file(
+    "resource/interface_traits.hpp.em"
+    "${CMAKE_CURRENT_BINARY_DIR}/${interface_name}_traits.hpp.em.watch"
+    COPYONLY
+  )
+  set(python_${interface_name}_traits
+    "import em"
+    "em.invoke(['-D', 'interface_name = \\'${interface_name}\\'', '-o', 'include/rclcpp/node_interfaces/${interface_name}_traits.hpp', '${CMAKE_CURRENT_SOURCE_DIR}/resource/interface_traits.hpp.em'])")
+  string(REPLACE ";" "$<SEMICOLON>" python_${interface_name}_traits "${python_${interface_name}_traits}")
+  add_custom_command(OUTPUT include/rclcpp/node_interfaces/${interface_name}_traits.hpp
+    COMMAND ${CMAKE_COMMAND} -E make_directory "include/rclcpp/node_interfaces"
+    COMMAND ${PYTHON_EXECUTABLE} ARGS -c "${python_${interface_name}_traits}"
+    DEPENDS "${CMAKE_CURRENT_BINARY_DIR}/${interface_name}_traits.hpp.em.watch"
+    COMMENT "Expanding interface_traits.hpp.em into ${interface_name}_traits.hpp"
+    VERBATIM
+  )
+  list(APPEND ${PROJECT_NAME}_SRCS
+    include/rclcpp/node_interfaces/${interface_name}_traits.hpp)
+
+  # "watch" template for changes
+  configure_file(
+    "resource/get_interface.hpp.em"
+    "get_${interface_name}.hpp.em.watch"
+    COPYONLY
+  )
+  set(python_get_${interface_name}
+    "import em"
+    "em.invoke(['-D', 'interface_name = \\'${interface_name}\\'', '-o', 'include/rclcpp/node_interfaces/get_${interface_name}.hpp', '${CMAKE_CURRENT_SOURCE_DIR}/resource/get_interface.hpp.em'])")
+  string(REPLACE ";" "$<SEMICOLON>" python_get_${interface_name} "${python_get_${interface_name}}")
+  add_custom_command(OUTPUT include/rclcpp/node_interfaces/get_${interface_name}.hpp
+    COMMAND ${CMAKE_COMMAND} -E make_directory "include/rclcpp/node_interfaces"
+    COMMAND ${PYTHON_EXECUTABLE} ARGS -c "${python_get_${interface_name}}"
+    DEPENDS "${CMAKE_CURRENT_BINARY_DIR}/get_${interface_name}.hpp.em.watch"
+    COMMENT "Expanding get_interface.hpp.em into get_${interface_file}.hpp"
+    VERBATIM
+  )
+  list(APPEND ${PROJECT_NAME}_SRCS
+    include/rclcpp/node_interfaces/get_${interface_name}.hpp)
+endforeach()
+
 include_directories("${CMAKE_CURRENT_BINARY_DIR}/include")
 
 add_library(${PROJECT_NAME}
@@ -532,6 +578,14 @@ if(BUILD_TESTING)
     target_link_libraries(test_init ${PROJECT_NAME})
   endif()
 
+  ament_add_gtest(test_interface_traits test/test_interface_traits.cpp
+    APPEND_LIBRARY_DIRS "${append_library_dirs}")
+  if(TARGET test_interface_traits)
+    ament_target_dependencies(test_interface_traits
+      "rcl")
+    target_link_libraries(test_interface_traits ${PROJECT_NAME})
+  endif()
+
   ament_add_gtest(test_multi_threaded_executor test/executors/test_multi_threaded_executor.cpp
     APPEND_LIBRARY_DIRS "${append_library_dirs}")
   if(TARGET test_multi_threaded_executor)

rclcpp/include/rclcpp/create_timer.hpp

@@ -32,8 +32,8 @@ namespace rclcpp
 template<typename CallbackT>
 typename rclcpp::TimerBase::SharedPtr
 create_timer(
-  node_interfaces::NodeBaseInterface * node_base,
+  std::shared_ptr<node_interfaces::NodeBaseInterface> node_base,
-  node_interfaces::NodeTimersInterface * node_timers,
+  std::shared_ptr<node_interfaces::NodeTimersInterface> node_timers,
   rclcpp::Clock::SharedPtr clock,
   rclcpp::Duration period,
   CallbackT && callback,

rclcpp/include/rclcpp/node_interfaces/get_node_base_interface.hpp

@@ -1,149 +0,0 @@
-// Copyright 2019 Open Source Robotics Foundation, Inc.
-//
-// Licensed under the Apache License, Version 2.0 (the "License");
-// you may not use this file except in compliance with the License.
-// You may obtain a copy of the License at
-//
-//     http://www.apache.org/licenses/LICENSE-2.0
-//
-// Unless required by applicable law or agreed to in writing, software
-// distributed under the License is distributed on an "AS IS" BASIS,
-// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-// See the License for the specific language governing permissions and
-// limitations under the License.
-
-#ifndef RCLCPP__NODE_INTERFACES__GET_NODE_BASE_INTERFACE_HPP_
-#define RCLCPP__NODE_INTERFACES__GET_NODE_BASE_INTERFACE_HPP_
-
-#include <memory>
-#include <utility>
-#include <type_traits>
-
-#include "rclcpp/node_interfaces/node_base_interface.hpp"
-
-/// This header provides the get_node_base_interface() template function.
-/**
- * This function is useful for getting the NodeBaseInterface pointer from
- * various kinds of Node-like classes.
- *
- * It's able to get the NodeBaseInterface pointer so long as the class
- * has a method called ``get_node_base_interface()`` which returns
- * either a pointer (const or not) to a NodeBaseInterface or a
- * std::shared_ptr to a NodeBaseInterface.
- */
-
-namespace rclcpp
-{
-namespace node_interfaces
-{
-
-namespace detail
-{
-
-// This is a meta-programming checker for if a given Node-like object has a
-// getter called get_node_base_interface() which returns various types,
-// e.g. const pointer or a shared pointer.
-template<typename NodeType, typename ReturnType>
-struct has_get_node_base_interface
-{
-private:
-  template<typename T>
-  static constexpr
-  auto
-  check(T *)->typename std::is_same<
-    decltype(std::declval<T>().get_node_base_interface()),
-    ReturnType
-  >::type;
-
-  template<typename>
-  static constexpr
-  std::false_type
-  check(...);
-
-public:
-  using type = decltype(check<NodeType>(nullptr));
-  static constexpr bool value = type::value;
-};
-
-// If NodeType is a pointer to NodeBaseInterface already (just normal function overload).
-inline
-rclcpp::node_interfaces::NodeBaseInterface *
-get_node_base_interface_from_pointer(rclcpp::node_interfaces::NodeBaseInterface * pointer)
-{
-  return pointer;
-}
-
-// If NodeType has a method called get_node_base_interface() which returns a shared pointer.
-template<
-  typename NodeType,
-  typename std::enable_if<has_get_node_base_interface<
-    typename std::remove_pointer<NodeType>::type,
-    std::shared_ptr<rclcpp::node_interfaces::NodeBaseInterface>
-  >::value, int>::type = 0
->
-rclcpp::node_interfaces::NodeBaseInterface *
-get_node_base_interface_from_pointer(NodeType node_pointer)
-{
-  return node_pointer->get_node_base_interface().get();
-}
-
-// If NodeType has a method called get_node_base_interface() which returns a pointer.
-template<
-  typename NodeType,
-  typename std::enable_if<has_get_node_base_interface<
-    typename std::remove_pointer<NodeType>::type,
-    rclcpp::node_interfaces::NodeBaseInterface *
-  >::value, int>::type = 0
->
-rclcpp::node_interfaces::NodeBaseInterface *
-get_node_base_interface_from_pointer(NodeType node_pointer)
-{
-  return node_pointer->get_node_base_interface();
-}
-
-// Forward shared_ptr's to const node pointer signatures.
-template<
-  typename NodeType,
-  typename std::enable_if<std::is_same<
-    NodeType,
-    typename std::shared_ptr<typename std::remove_pointer<NodeType>::type::element_type> *
-  >::value, int>::type = 0
->
-rclcpp::node_interfaces::NodeBaseInterface *
-get_node_base_interface_from_pointer(NodeType node_shared_pointer)
-{
-  return get_node_base_interface_from_pointer(node_shared_pointer->get());
-}
-
-}  // namespace detail
-
-/// Get the NodeBaseInterface as a pointer from a pointer to a "Node like" object.
-template<
-  typename NodeType,
-  typename std::enable_if<std::is_pointer<NodeType>::value, int>::type = 0
->
-rclcpp::node_interfaces::NodeBaseInterface *
-get_node_base_interface(NodeType node_pointer)
-{
-  // Forward pointers to detail implmentation directly.
-  return detail::get_node_base_interface_from_pointer(node_pointer);
-}
-
-/// Get the NodeBaseInterface as a pointer from a "Node like" object.
-template<
-  typename NodeType,
-  typename std::enable_if<
-    !std::is_pointer<typename std::remove_reference<NodeType>::type>::value, int
-  >::type = 0
->
-rclcpp::node_interfaces::NodeBaseInterface *
-get_node_base_interface(NodeType && node_reference)
-{
-  // Forward references to detail implmentation as a pointer.
-  return detail::get_node_base_interface_from_pointer(&node_reference);
-}
-
-}  // namespace node_interfaces
-}  // namespace rclcpp
-
-#endif  // RCLCPP__NODE_INTERFACES__GET_NODE_BASE_INTERFACE_HPP_

rclcpp/include/rclcpp/node_interfaces/get_node_timers_interface.hpp

@@ -1,149 +0,0 @@
-// Copyright 2019 Open Source Robotics Foundation, Inc.
-//
-// Licensed under the Apache License, Version 2.0 (the "License");
-// you may not use this file except in compliance with the License.
-// You may obtain a copy of the License at
-//
-//     http://www.apache.org/licenses/LICENSE-2.0
-//
-// Unless required by applicable law or agreed to in writing, software
-// distributed under the License is distributed on an "AS IS" BASIS,
-// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-// See the License for the specific language governing permissions and
-// limitations under the License.
-
-#ifndef RCLCPP__NODE_INTERFACES__GET_NODE_TIMERS_INTERFACE_HPP_
-#define RCLCPP__NODE_INTERFACES__GET_NODE_TIMERS_INTERFACE_HPP_
-
-#include <memory>
-#include <utility>
-#include <type_traits>
-
-#include "rclcpp/node_interfaces/node_timers_interface.hpp"
-
-/// This header provides the get_node_timers_interface() template function.
-/**
- * This function is useful for getting the NodeTimersInterface pointer from
- * various kinds of Node-like classes.
- *
- * It's able to get the NodeTimersInterface pointer so long as the class
- * has a method called ``get_node_timers_interface()`` which returns
- * either a pointer (const or not) to a NodeTimersInterface or a
- * std::shared_ptr to a NodeTimersInterface.
- */
-
-namespace rclcpp
-{
-namespace node_interfaces
-{
-
-namespace detail
-{
-
-// This is a meta-programming checker for if a given Node-like object has a
-// getter called get_node_timers_interface() which returns various types,
-// e.g. const pointer or a shared pointer.
-template<typename NodeType, typename ReturnType>
-struct has_get_node_timers_interface
-{
-private:
-  template<typename T>
-  static constexpr
-  auto
-  check(T *)->typename std::is_same<
-    decltype(std::declval<T>().get_node_timers_interface()),
-    ReturnType
-  >::type;
-
-  template<typename>
-  static constexpr
-  std::false_type
-  check(...);
-
-public:
-  using type = decltype(check<NodeType>(nullptr));
-  static constexpr bool value = type::value;
-};
-
-// If NodeType is a pointer to NodeTimersInterface already (just normal function overload).
-inline
-rclcpp::node_interfaces::NodeTimersInterface *
-get_node_timers_interface_from_pointer(rclcpp::node_interfaces::NodeTimersInterface * pointer)
-{
-  return pointer;
-}
-
-// If NodeType has a method called get_node_timers_interface() which returns a shared pointer.
-template<
-  typename NodeType,
-  typename std::enable_if<has_get_node_timers_interface<
-    typename std::remove_pointer<NodeType>::type,
-    std::shared_ptr<rclcpp::node_interfaces::NodeTimersInterface>
-  >::value, int>::type = 0
->
-rclcpp::node_interfaces::NodeTimersInterface *
-get_node_timers_interface_from_pointer(NodeType node_pointer)
-{
-  return node_pointer->get_node_timers_interface().get();
-}
-
-// If NodeType has a method called get_node_timers_interface() which returns a pointer.
-template<
-  typename NodeType,
-  typename std::enable_if<has_get_node_timers_interface<
-    typename std::remove_pointer<NodeType>::type,
-    rclcpp::node_interfaces::NodeTimersInterface *
-  >::value, int>::type = 0
->
-rclcpp::node_interfaces::NodeTimersInterface *
-get_node_timers_interface_from_pointer(NodeType node_pointer)
-{
-  return node_pointer->get_node_timers_interface();
-}
-
-// Forward shared_ptr's to const node pointer signatures.
-template<
-  typename NodeType,
-  typename std::enable_if<std::is_same<
-    NodeType,
-    typename std::shared_ptr<typename std::remove_pointer<NodeType>::type::element_type> *
-  >::value, int>::type = 0
->
-rclcpp::node_interfaces::NodeTimersInterface *
-get_node_timers_interface_from_pointer(NodeType node_shared_pointer)
-{
-  return get_node_timers_interface_from_pointer(node_shared_pointer->get());
-}
-
-}  // namespace detail
-
-/// Get the NodeTimersInterface as a pointer from a pointer to a "Node like" object.
-template<
-  typename NodeType,
-  typename std::enable_if<std::is_pointer<NodeType>::value, int>::type = 0
->
-rclcpp::node_interfaces::NodeTimersInterface *
-get_node_timers_interface(NodeType node_pointer)
-{
-  // Forward pointers to detail implmentation directly.
-  return detail::get_node_timers_interface_from_pointer(node_pointer);
-}
-
-/// Get the NodeTimersInterface as a pointer from a "Node like" object.
-template<
-  typename NodeType,
-  typename std::enable_if<
-    !std::is_pointer<typename std::remove_reference<NodeType>::type>::value, int
-  >::type = 0
->
-rclcpp::node_interfaces::NodeTimersInterface *
-get_node_timers_interface(NodeType && node_reference)
-{
-  // Forward references to detail implmentation as a pointer.
-  return detail::get_node_timers_interface_from_pointer(&node_reference);
-}
-
-}  // namespace node_interfaces
-}  // namespace rclcpp
-
-#endif  // RCLCPP__NODE_INTERFACES__GET_NODE_TIMERS_INTERFACE_HPP_

rclcpp/include/rclcpp/node_interfaces/get_node_topics_interface.hpp

@@ -1,149 +0,0 @@
-// Copyright 2019 Open Source Robotics Foundation, Inc.
-//
-// Licensed under the Apache License, Version 2.0 (the "License");
-// you may not use this file except in compliance with the License.
-// You may obtain a copy of the License at
-//
-//     http://www.apache.org/licenses/LICENSE-2.0
-//
-// Unless required by applicable law or agreed to in writing, software
-// distributed under the License is distributed on an "AS IS" BASIS,
-// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-// See the License for the specific language governing permissions and
-// limitations under the License.
-
-#ifndef RCLCPP__NODE_INTERFACES__GET_NODE_TOPICS_INTERFACE_HPP_
-#define RCLCPP__NODE_INTERFACES__GET_NODE_TOPICS_INTERFACE_HPP_
-
-#include <memory>
-#include <utility>
-#include <type_traits>
-
-#include "rclcpp/node_interfaces/node_topics_interface.hpp"
-
-/// This header provides the get_node_topics_interface() template function.
-/**
- * This function is useful for getting the NodeTopicsInterface pointer from
- * various kinds of Node-like classes.
- *
- * It's able to get the NodeTopicsInterface pointer so long as the class
- * has a method called ``get_node_topics_interface()`` which returns
- * either a pointer (const or not) to a NodeTopicsInterface or a
- * std::shared_ptr to a NodeTopicsInterface.
- */
-
-namespace rclcpp
-{
-namespace node_interfaces
-{
-
-namespace detail
-{
-
-// This is a meta-programming checker for if a given Node-like object has a
-// getter called get_node_topics_interface() which returns various types,
-// e.g. const pointer or a shared pointer.
-template<typename NodeType, typename ReturnType>
-struct has_get_node_topics_interface
-{
-private:
-  template<typename T>
-  static constexpr
-  auto
-  check(T *)->typename std::is_same<
-    decltype(std::declval<T>().get_node_topics_interface()),
-    ReturnType
-  >::type;
-
-  template<typename>
-  static constexpr
-  std::false_type
-  check(...);
-
-public:
-  using type = decltype(check<NodeType>(nullptr));
-  static constexpr bool value = type::value;
-};
-
-// If NodeType is a pointer to NodeTopicsInterface already (just normal function overload).
-inline
-rclcpp::node_interfaces::NodeTopicsInterface *
-get_node_topics_interface_from_pointer(rclcpp::node_interfaces::NodeTopicsInterface * pointer)
-{
-  return pointer;
-}
-
-// If NodeType has a method called get_node_topics_interface() which returns a shared pointer.
-template<
-  typename NodeType,
-  typename std::enable_if<has_get_node_topics_interface<
-    typename std::remove_pointer<NodeType>::type,
-    std::shared_ptr<rclcpp::node_interfaces::NodeTopicsInterface>
-  >::value, int>::type = 0
->
-rclcpp::node_interfaces::NodeTopicsInterface *
-get_node_topics_interface_from_pointer(NodeType node_pointer)
-{
-  return node_pointer->get_node_topics_interface().get();
-}
-
-// If NodeType has a method called get_node_topics_interface() which returns a pointer.
-template<
-  typename NodeType,
-  typename std::enable_if<has_get_node_topics_interface<
-    typename std::remove_pointer<NodeType>::type,
-    rclcpp::node_interfaces::NodeTopicsInterface *
-  >::value, int>::type = 0
->
-rclcpp::node_interfaces::NodeTopicsInterface *
-get_node_topics_interface_from_pointer(NodeType node_pointer)
-{
-  return node_pointer->get_node_topics_interface();
-}
-
-// Forward shared_ptr's to const node pointer signatures.
-template<
-  typename NodeType,
-  typename std::enable_if<std::is_same<
-    NodeType,
-    typename std::shared_ptr<typename std::remove_pointer<NodeType>::type::element_type> *
-  >::value, int>::type = 0
->
-rclcpp::node_interfaces::NodeTopicsInterface *
-get_node_topics_interface_from_pointer(NodeType node_shared_pointer)
-{
-  return get_node_topics_interface_from_pointer(node_shared_pointer->get());
-}
-
-}  // namespace detail
-
-/// Get the NodeTopicsInterface as a pointer from a pointer to a "Node like" object.
-template<
-  typename NodeType,
-  typename std::enable_if<std::is_pointer<NodeType>::value, int>::type = 0
->
-rclcpp::node_interfaces::NodeTopicsInterface *
-get_node_topics_interface(NodeType node_pointer)
-{
-  // Forward pointers to detail implmentation directly.
-  return detail::get_node_topics_interface_from_pointer(node_pointer);
-}
-
-/// Get the NodeTopicsInterface as a pointer from a "Node like" object.
-template<
-  typename NodeType,
-  typename std::enable_if<
-    !std::is_pointer<typename std::remove_reference<NodeType>::type>::value, int
-  >::type = 0
->
-rclcpp::node_interfaces::NodeTopicsInterface *
-get_node_topics_interface(NodeType && node_reference)
-{
-  // Forward references to detail implmentation as a pointer.
-  return detail::get_node_topics_interface_from_pointer(&node_reference);
-}
-
-}  // namespace node_interfaces
-}  // namespace rclcpp
-
-#endif  // RCLCPP__NODE_INTERFACES__GET_NODE_TOPICS_INTERFACE_HPP_

rclcpp/resource/get_interface.hpp.em

@@ -0,0 +1,111 @@
+// Copyright 2020 Open Source Robotics Foundation, Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+@{
+uppercase_interface_name = interface_name.upper()
+}@
+
+#ifndef RCLCPP__NODE_INTERFACES__GET_@(uppercase_interface_name)_HPP_
+#define RCLCPP__NODE_INTERFACES__GET_@(uppercase_interface_name)_HPP_
+
+#include <memory>
+#include <utility>
+#include <type_traits>
+
+#include "rcpputils/pointer_traits.hpp"
+
+#include "rclcpp/node_interfaces/@(interface_name).hpp"
+#include "rclcpp/node_interfaces/@(interface_name)_traits.hpp"
+
+@{
+interface_typename = ''.join([part.capitalize() for part in interface_name.split('_')])
+}@
+
+/// This header provides the get_@(interface_name)() template function.
+/**
+ * This function is useful for getting the @(interface_typename) pointer from
+ * various kinds of Node-like classes.
+ *
+ * It's able to get a std::shared_ptr to a @(interface_typename) so long as the class
+ * has a method called ``get_@(interface_name)()`` which returns one.
+ */
+
+namespace rclcpp
+{
+namespace node_interfaces
+{
+namespace detail
+{
+
+// If NodeType has a method called get_@(interface_name)() which returns a shared pointer.
+template<
+  typename NodeType,
+  typename std::enable_if<has_@(interface_name)<
+    typename rcpputils::remove_pointer<NodeType>::type
+  >::value, int>::type = 0
+>
+std::shared_ptr<rclcpp::node_interfaces::@(interface_typename)>
+get_@(interface_name)_from_pointer(NodeType node_pointer)
+{
+  if (!node_pointer) {
+    throw std::invalid_argument("node cannot be nullptr");
+  }
+  return node_pointer->get_@(interface_name)();
+}
+
+}  // namespace detail
+
+/// Get the @(interface_typename) as a shared pointer from a pointer to a "Node like" object.
+template<
+  typename NodeType,
+  typename std::enable_if<
+    rcpputils::is_pointer<NodeType>::value, int
+  >::type = 0
+>
+inline
+std::shared_ptr<rclcpp::node_interfaces::@(interface_typename)>
+get_@(interface_name)(NodeType && node)
+{
+  // Forward pointers to detail implementation directly.
+  return detail::get_@(interface_name)_from_pointer(node);
+}
+
+/// Get the @(interface_typename) as a shared pointer from a "Node like" object.
+template<
+  typename NodeType,
+  typename std::enable_if<
+    !rcpputils::is_pointer<NodeType>::value, int
+  >::type = 0
+>
+inline
+std::shared_ptr<rclcpp::node_interfaces::@(interface_typename)>
+get_@(interface_name)(NodeType && node)
+{
+  // Forward references to detail implementation as a pointer.
+  return detail::get_@(interface_name)_from_pointer(&node);
+}
+
+/// Keep the @(interface_typename) a shared pointer.
+inline
+std::shared_ptr<rclcpp::node_interfaces::@(interface_typename)>
+get_@(interface_name)(
+  std::shared_ptr<rclcpp::node_interfaces::@(interface_typename)> & node_interface)
+{
+  return node_interface;
+}
+
+}  // namespace node_interfaces
+}  // namespace rclcpp
+
+#endif  // RCLCPP__NODE_INTERFACES__GET_@(uppercase_interface_name)_HPP_

rclcpp/resource/interface_traits.hpp.em

@@ -0,0 +1,47 @@
+// Copyright 2020 Open Source Robotics Foundation, Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+@{
+uppercase_interface_name = interface_name.upper()
+interface_typename = ''.join([part.capitalize() for part in interface_name.split('_')])
+}@
+
+#ifndef RCLCPP__NODE_INTERFACES__@(uppercase_interface_name)_TRAITS_HPP_
+#define RCLCPP__NODE_INTERFACES__@(uppercase_interface_name)_TRAITS_HPP_
+
+#include <functional>
+#include <type_traits>
+
+#include "rclcpp/node_interfaces/@(interface_name).hpp"
+
+namespace rclcpp
+{
+namespace node_interfaces
+{
+
+template<class T, typename = void>
+struct has_@(interface_name) : std::false_type
+{};
+
+template<class T>
+struct has_@(interface_name)<
+  T, typename std::enable_if<
+    std::is_same<
+      std::shared_ptr<rclcpp::node_interfaces::@(interface_typename)>,
+      decltype(std::declval<T>().get_@(interface_name)())>::value>::type> : std::true_type
+{};
+
+}  // namespace node_interfaces
+}  // namespace rclcpp
+
+#endif  // RCLCPP__NODE_INTERFACES__@(uppercase_interface_name)_TRAITS_HPP_

rclcpp/test/node_interfaces/test_get_node_interfaces.cpp

@@ -47,22 +47,38 @@ protected:
 rclcpp::Node::SharedPtr TestGetNodeInterfaces::node = nullptr;
 std::shared_ptr<NodeWrapper> TestGetNodeInterfaces::wrapped_node = nullptr;
 
+TEST_F(TestGetNodeInterfaces, null_rclcpp_node_shared_ptr) {
+  rclcpp::Node::SharedPtr null_node;
+  EXPECT_THROW(
+  {
+    rclcpp::node_interfaces::get_node_topics_interface(null_node);
+  }, std::invalid_argument);
+}
+
 TEST_F(TestGetNodeInterfaces, rclcpp_node_shared_ptr) {
   auto result = rclcpp::node_interfaces::get_node_topics_interface(this->node);
   static_assert(
     std::is_same<
-      rclcpp::node_interfaces::NodeTopicsInterface *,
+      std::shared_ptr<rclcpp::node_interfaces::NodeTopicsInterface>,
       decltype(result)
-    >::value, "expected rclcpp::node_interfaces::NodeTopicsInterface *");
+    >::value, "expected std::shared_ptr<rclcpp::node_interfaces::NodeTopicsInterface>");
+}
+
+TEST_F(TestGetNodeInterfaces, null_node_shared_ptr) {
+  std::shared_ptr<NodeWrapper> null_node;
+  EXPECT_THROW(
+  {
+    rclcpp::node_interfaces::get_node_topics_interface(null_node);
+  }, std::invalid_argument);
 }
 
 TEST_F(TestGetNodeInterfaces, node_shared_ptr) {
   auto result = rclcpp::node_interfaces::get_node_topics_interface(this->wrapped_node);
   static_assert(
     std::is_same<
-      rclcpp::node_interfaces::NodeTopicsInterface *,
+      std::shared_ptr<rclcpp::node_interfaces::NodeTopicsInterface>,
       decltype(result)
-    >::value, "expected rclcpp::node_interfaces::NodeTopicsInterface *");
+    >::value, "expected std::shared_ptr<rclcpp::node_interfaces::NodeTopicsInterface>");
 }
 
 TEST_F(TestGetNodeInterfaces, rclcpp_node_reference) {
@@ -70,9 +86,9 @@ TEST_F(TestGetNodeInterfaces, rclcpp_node_reference) {
   auto result = rclcpp::node_interfaces::get_node_topics_interface(node_reference);
   static_assert(
     std::is_same<
-      rclcpp::node_interfaces::NodeTopicsInterface *,
+      std::shared_ptr<rclcpp::node_interfaces::NodeTopicsInterface>,
       decltype(result)
-    >::value, "expected rclcpp::node_interfaces::NodeTopicsInterface *");
+    >::value, "expected std::shared_ptr<rclcpp::node_interfaces::NodeTopicsInterface>");
 }
 
 TEST_F(TestGetNodeInterfaces, node_reference) {
@@ -80,9 +96,9 @@ TEST_F(TestGetNodeInterfaces, node_reference) {
   auto result = rclcpp::node_interfaces::get_node_topics_interface(wrapped_node_reference);
   static_assert(
     std::is_same<
-      rclcpp::node_interfaces::NodeTopicsInterface *,
+      std::shared_ptr<rclcpp::node_interfaces::NodeTopicsInterface>,
       decltype(result)
-    >::value, "expected rclcpp::node_interfaces::NodeTopicsInterface *");
+    >::value, "expected std::shared_ptr<rclcpp::node_interfaces::NodeTopicsInterface>");
 }
 
 TEST_F(TestGetNodeInterfaces, rclcpp_node_pointer) {
@@ -90,9 +106,17 @@ TEST_F(TestGetNodeInterfaces, rclcpp_node_pointer) {
   auto result = rclcpp::node_interfaces::get_node_topics_interface(node_pointer);
   static_assert(
     std::is_same<
-      rclcpp::node_interfaces::NodeTopicsInterface *,
+      std::shared_ptr<rclcpp::node_interfaces::NodeTopicsInterface>,
       decltype(result)
-    >::value, "expected rclcpp::node_interfaces::NodeTopicsInterface *");
+    >::value, "expected std::shared_ptr<rclcpp::node_interfaces::NodeTopicsInterface>");
+}
+
+TEST_F(TestGetNodeInterfaces, null_rclcpp_node_pointer) {
+  rclcpp::Node * null_node{nullptr};
+  EXPECT_THROW(
+  {
+    rclcpp::node_interfaces::get_node_topics_interface(null_node);
+  }, std::invalid_argument);
 }
 
 TEST_F(TestGetNodeInterfaces, node_pointer) {
@@ -100,9 +124,17 @@ TEST_F(TestGetNodeInterfaces, node_pointer) {
   auto result = rclcpp::node_interfaces::get_node_topics_interface(wrapped_node_pointer);
   static_assert(
     std::is_same<
-      rclcpp::node_interfaces::NodeTopicsInterface *,
+      std::shared_ptr<rclcpp::node_interfaces::NodeTopicsInterface>,
       decltype(result)
-    >::value, "expected rclcpp::node_interfaces::NodeTopicsInterface *");
+    >::value, "expected std::shared_ptr<rclcpp::node_interfaces::NodeTopicsInterface>");
+}
+
+TEST_F(TestGetNodeInterfaces, null_node_pointer) {
+  NodeWrapper * null_node{nullptr};
+  EXPECT_THROW(
+  {
+    rclcpp::node_interfaces::get_node_topics_interface(null_node);
+  }, std::invalid_argument);
 }
 
 TEST_F(TestGetNodeInterfaces, interface_shared_pointer) {
@@ -111,7 +143,7 @@ TEST_F(TestGetNodeInterfaces, interface_shared_pointer) {
   auto result = rclcpp::node_interfaces::get_node_topics_interface(interface_shared_ptr);
   static_assert(
     std::is_same<
-      rclcpp::node_interfaces::NodeTopicsInterface *,
+      std::shared_ptr<rclcpp::node_interfaces::NodeTopicsInterface>,
       decltype(result)
-    >::value, "expected rclcpp::node_interfaces::NodeTopicsInterface *");
+    >::value, "expected std::shared_ptr<rclcpp::node_interfaces::NodeTopicsInterface>");
 }

rclcpp/test/test_interface_traits.cpp

@@ -0,0 +1,77 @@
+// Copyright 2019 Open Source Robotics Foundation, Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include <gtest/gtest.h>
+
+#include <memory>
+#include <utility>
+
+#include "rclcpp/contexts/default_context.hpp"
+#include "rclcpp/node_interfaces/node_base_interface_traits.hpp"
+#include "rclcpp/node_interfaces/node_base.hpp"
+#include "rclcpp/node.hpp"
+
+class MyNode
+{
+public:
+  std::shared_ptr<rclcpp::node_interfaces::NodeBaseInterface> get_node_base_interface() const
+  {
+    rclcpp::NodeOptions options;
+    return std::make_shared<rclcpp::node_interfaces::NodeBase>(
+      "my_node_name",
+      "my_node_namespace",
+      rclcpp::contexts::default_context::get_global_default_context(),
+      *options.get_rcl_node_options(),
+      false);
+  }
+};
+
+class WrongNode
+{
+public:
+  std::shared_ptr<rclcpp::node_interfaces::NodeBaseInterface> not_get_node_base_interface()
+  {
+    return nullptr;
+  }
+};
+
+template<class T, typename std::enable_if<
+    rclcpp::node_interfaces::has_node_base_interface<T>::value
+  >::type * = nullptr>
+void get_node_name(const T & nodelike)
+{
+  ASSERT_STREQ("my_node_name", nodelike.get_node_base_interface()->get_name());
+}
+
+class TestInterfaceTraits : public ::testing::Test
+{
+protected:
+  static void SetUpTestCase()
+  {
+    rclcpp::init(0, nullptr);
+  }
+
+  static void TearDownTestCase()
+  {
+    rclcpp::shutdown();
+  }
+};
+
+TEST_F(TestInterfaceTraits, has_node_base_interface) {
+  ASSERT_TRUE(rclcpp::node_interfaces::has_node_base_interface<MyNode>::value);
+  ASSERT_FALSE(rclcpp::node_interfaces::has_node_base_interface<WrongNode>::value);
+  ASSERT_TRUE(rclcpp::node_interfaces::has_node_base_interface<rclcpp::Node>::value);
+
+  get_node_name(MyNode());
+}