add parameter helpers (redo of #233) (#237)

* add parameter helpers

* respond to comments

* remove unnecessary indent comments

* replace temp variable assignment with explicit constructor invocation

rclcpp/include/rclcpp/parameter.hpp

@@ -80,6 +80,8 @@ public:
   rcl_interfaces::msg::ParameterValue
   get_parameter_value() const;
 
+  // The following get_value() variants require the use of ParameterType
+
   template<ParameterType type>
   typename std::enable_if<type == ParameterType::PARAMETER_INTEGER, int64_t>::type
   get_value() const
@@ -125,8 +127,8 @@ public:
   }
 
   template<ParameterType type>
-  typename std::enable_if<type == ParameterType::PARAMETER_BYTES,
-  const std::vector<uint8_t> &>::type
+  typename std::enable_if<
+    type == ParameterType::PARAMETER_BYTES, const std::vector<uint8_t> &>::type
   get_value() const
   {
     if (value_.type != rcl_interfaces::msg::ParameterType::PARAMETER_BYTES) {
@@ -136,6 +138,46 @@ public:
     return value_.bytes_value;
   }
 
+  // The following get_value() variants allow the use of primitive types
+
+  template<typename type>
+  typename std::enable_if<
+    std::is_integral<type>::value && !std::is_same<type, bool>::value, int64_t>::type
+  get_value() const
+  {
+    return get_value<ParameterType::PARAMETER_INTEGER>();
+  }
+
+  template<typename type>
+  typename std::enable_if<std::is_floating_point<type>::value, double>::type
+  get_value() const
+  {
+    return get_value<ParameterType::PARAMETER_DOUBLE>();
+  }
+
+  template<typename type>
+  typename std::enable_if<std::is_convertible<type, std::string>::value, const std::string &>::type
+  get_value() const
+  {
+    return get_value<ParameterType::PARAMETER_STRING>();
+  }
+
+  template<typename type>
+  typename std::enable_if<std::is_same<type, bool>::value, bool>::type
+  get_value() const
+  {
+    return get_value<ParameterType::PARAMETER_BOOL>();
+  }
+
+  template<typename type>
+  typename std::enable_if<
+    std::is_convertible<
+      type, const std::vector<uint8_t> &>::value, const std::vector<uint8_t> &>::type
+  get_value() const
+  {
+    return get_value<ParameterType::PARAMETER_BYTES>();
+  }
+
   RCLCPP_PUBLIC
   int64_t
   as_int() const;

rclcpp/include/rclcpp/parameter_client.hpp

@@ -134,6 +134,45 @@ public:
   std::vector<rclcpp::parameter::ParameterVariant>
   get_parameters(const std::vector<std::string> & parameter_names);
 
+  RCLCPP_PUBLIC
+  bool
+  has_parameter(const std::string & parameter_name);
+
+  template<typename T>
+  T
+  get_parameter_impl(
+    const std::string & parameter_name, std::function<T()> parameter_not_found_handler)
+  {
+    std::vector<std::string> names;
+    names.push_back(parameter_name);
+    auto vars = get_parameters(names);
+    if ((vars.size() != 1) || (vars[0].get_type() == rclcpp::parameter::PARAMETER_NOT_SET)) {
+      return parameter_not_found_handler();
+    } else {
+      return static_cast<T>(vars[0].get_value<T>());
+    }
+  }
+
+  template<typename T>
+  T
+  get_parameter(const std::string & parameter_name, const T & default_value)
+  {
+    // *INDENT-OFF*
+    return get_parameter_impl(parameter_name,
+      std::function<T()>([&default_value]() -> T {return default_value; }));
+    // *INDENT-ON*
+  }
+
+  template<typename T>
+  T
+  get_parameter(const std::string & parameter_name)
+  {
+    // *INDENT-OFF*
+    return get_parameter_impl(parameter_name,
+      std::function<T()>([]() -> T {throw std::runtime_error("Parameter not set"); }));
+    // *INDENT-ON*
+  }
+
   RCLCPP_PUBLIC
   std::vector<rclcpp::parameter::ParameterType>
   get_parameter_types(const std::vector<std::string> & parameter_names);

rclcpp/src/rclcpp/parameter_client.cpp

@@ -259,6 +259,15 @@ SyncParametersClient::get_parameters(const std::vector<std::string> & parameter_
   return std::vector<rclcpp::parameter::ParameterVariant>();
 }
 
+bool
+SyncParametersClient::has_parameter(const std::string & parameter_name)
+{
+  std::vector<std::string> names;
+  names.push_back(parameter_name);
+  auto vars = list_parameters(names, 1);
+  return vars.names.size() > 0;
+}
+
 std::vector<rclcpp::parameter::ParameterType>
 SyncParametersClient::get_parameter_types(const std::vector<std::string> & parameter_names)
 {