Template Class Subscription

Defined in File subscription.hpp

Inheritance Relationships

Base Type

public rclcpp::SubscriptionBase (Class SubscriptionBase)

Class Documentation

template<typename MessageT, typename AllocatorT = std::allocator<void>, typename SubscribedT = typename rclcpp::TypeAdapter<MessageT>::custom_type, typename ROSMessageT = typename rclcpp::TypeAdapter<MessageT>::ros_message_type, typename MessageMemoryStrategyT = rclcpp::message_memory_strategy::MessageMemoryStrategy<ROSMessageT, AllocatorT>> class Subscription : public rclcpp::SubscriptionBase 

Subscription implementation, templated on the type of message this subscription receives.

Public Types

using SubscribedType = SubscribedT 

using ROSMessageType = ROSMessageT 

using MessageMemoryStrategyType = MessageMemoryStrategyT 

using SubscribedTypeAllocatorTraits = allocator::AllocRebind<SubscribedType, AllocatorT>

using SubscribedTypeAllocator = typename SubscribedTypeAllocatorTraits::allocator_type

using SubscribedTypeDeleter = allocator::Deleter<SubscribedTypeAllocator, SubscribedType>

using ROSMessageTypeAllocatorTraits = allocator::AllocRebind<ROSMessageType, AllocatorT>

using ROSMessageTypeAllocator = typename ROSMessageTypeAllocatorTraits::allocator_type

using ROSMessageTypeDeleter = allocator::Deleter<ROSMessageTypeAllocator, ROSMessageType>

using MessageAllocatorTraits = ROSMessageTypeAllocatorTraits 

using MessageAllocator = ROSMessageTypeAllocator 

using MessageDeleter = ROSMessageTypeDeleter 

using ConstMessageSharedPtr = std::shared_ptr<const ROSMessageType>

using MessageUniquePtr = std::unique_ptr<ROSMessageType, ROSMessageTypeDeleter>

Public Functions

inline Subscription(rclcpp::node_interfaces::NodeBaseInterface *node_base, const rosidl_message_type_support_t &type_support_handle, const std::string &topic_name, const rclcpp::QoS &qos, AnySubscriptionCallback<MessageT, AllocatorT> callback, const rclcpp::SubscriptionOptionsWithAllocator<AllocatorT> &options, typename MessageMemoryStrategyT::SharedPtr message_memory_strategy, SubscriptionTopicStatisticsSharedPtr subscription_topic_statistics = nullptr)

Default constructor.

The constructor for a subscription is almost never called directly. Instead, subscriptions should be instantiated through the function rclcpp::create_subscription().

Parameters:

node_base – [in] NodeBaseInterface pointer that is used in part of the setup.
type_support_handle – [in] rosidl type support struct, for the Message type of the topic.
topic_name – [in] Name of the topic to subscribe to.
qos – [in] QoS profile for Subcription.
callback – [in] User defined callback to call when a message is received.
options – [in] Options for the subscription.
message_memory_strategy – The memory strategy to be used for managing message memory.
subscription_topic_statistics – [in] Optional pointer to a topic statistics subcription.

Throws:

std::invalid_argument – if the QoS is uncompatible with intra-process (if one of the following conditions are true: qos_profile.history == RMW_QOS_POLICY_HISTORY_KEEP_ALL, qos_profile.depth == 0 or qos_profile.durability != RMW_QOS_POLICY_DURABILITY_VOLATILE).

inline void post_init_setup(rclcpp::node_interfaces::NodeBaseInterface *node_base, const rclcpp::QoS &qos, const rclcpp::SubscriptionOptionsWithAllocator<AllocatorT> &options): Called after construction to continue setup that requires shared_from_this().

inline bool take(ROSMessageType &message_out, rclcpp::MessageInfo &message_info_out)

Take the next message from the inter-process subscription.

Data may be taken (written) into the message_out and message_info_out even if false is returned. Specifically in the case of dropping redundant intra-process data, where data is received via both intra-process and inter-process (due to the underlying middleware being unabled to avoid this duplicate delivery) and so inter-process data from those intra-process publishers is ignored, but it has to be taken to know if it came from an intra-process publisher or not, and therefore could be dropped.