CapabilityClient< ActionT > Class Template Reference

The simplest possible way to ask a capability to do something. More...

#include <capability_client.hpp>

Classes
struct	Response
	Final outcome of a request, as delivered to a ResponseCallback or returned by request_and_wait(). More...

Public Types
using	SharedPtr = std::shared_ptr<CapabilityClient<ActionT>>
	Shared pointer to a CapabilityClient<ActionT>.
using	Goal = typename ActionT::Goal
	Goal type of the wrapped action.
using	Feedback = typename ActionT::Feedback
	Feedback type of the wrapped action.
using	Result = typename ActionT::Result
	Result type of the wrapped action.
using	FeedbackCallback = std::function<void (std::shared_ptr<const Feedback>)>
	Callback invoked with feedback as it arrives for the request.
using	Outcome = typename ActionClient<ActionT>::GoalOutcome
	Same vocabulary as ActionClient::GoalOutcome.
using	ResponseCallback = std::function<void (const Response &)>
	Callback invoked once a request reaches a final outcome.

Public Member Functions
	CapabilityClient (const CapabilityClient &)=delete
CapabilityClient &	operator= (const CapabilityClient &)=delete
bool	wait_for_capability ()
	Blocks until the capability is reachable, using the constructor's default_wait_timeout.
bool	wait_for_capability (std::chrono::milliseconds timeout)
	Blocks until the capability is reachable, or timeout elapses.
void	request (const Goal &goal, ResponseCallback on_response, FeedbackCallback on_feedback=nullptr)
	Asks the capability to do something.
Response	request_and_wait (const Goal &goal, FeedbackCallback on_feedback=nullptr, std::chrono::milliseconds timeout=std::chrono::milliseconds(0))
	Asks the capability to do something and blocks the calling thread until the response is ready (or timeout elapses, if positive).
void	cancel ()
	Asks the capability to stop whatever it is currently doing (e.g.

Static Public Member Functions
static SharedPtr	create (rclcpp::Node &node, const std::string &capability_name, std::chrono::milliseconds default_wait_timeout=std::chrono::seconds(5))
	Constructs a new client for the capability named capability_name.

Detailed Description

template<typename ActionT>
class easyfleet_core::CapabilityClient< ActionT >

The simplest possible way to ask a capability to do something.

Where ActionClient<ActionT> exposes the full action protocol (goal acceptance, per-goal cancellation by id, active goal bookkeeping...), CapabilityClient<ActionT> reduces that to the three things a caller of a capability actually cares about: send a request, optionally observe feedback while it runs, and get the final response. It talks to a capability by name, exactly as advertised by easyfleet_core::Capability (the capability name is the action name).

Usage:

auto nav = easyfleet_core::CapabilityClient<nav2_msgs::action::NavigateToPose>::create(
  this, "navigation");
if (!nav->wait_for_capability()) { ... not available ... }
 
using NavClient = easyfleet_core::CapabilityClient<nav2_msgs::action::NavigateToPose>;
nav2_msgs::action::NavigateToPose::Goal goal;
goal.pose = ...;
auto response = nav->request_and_wait(goal);
if (response.outcome == NavClient::Outcome::SUCCEEDED) { ... }

Member Function Documentation

cancel()

template<typename ActionT>

void cancel

(

)

Asks the capability to stop whatever it is currently doing (e.g.

a navigating robot stops moving, a perception stream stops reporting detections). Returns immediately; the pending request's on_response (from request()) or the return of request_and_wait() will resolve with Outcome::CANCELED once the capability has stopped.

create()

template<typename ActionT>

CapabilityClient< ActionT >::SharedPtr create ( rclcpp::Node & node, const std::string & capability_name, std::chrono::milliseconds default_wait_timeout = std::chrono::seconds(5) )

static

Constructs a new client for the capability named capability_name.

Parameters

node	Node on whose behalf the capability is called. Only used to construct the underlying ActionClient (never stored), so a reference – never null, unlike a pointer – is all this needs.
capability_name	Name of the capability to call (its action name).
default_wait_timeout	Timeout used by the no-argument overload of wait_for_capability().

Returns

A new CapabilityClient<ActionT>.

request()

template<typename ActionT>

void request	(	const Goal &	goal,
		ResponseCallback	on_response,
		FeedbackCallback	on_feedback = nullptr )

Asks the capability to do something.

Returns immediately; on_response is called exactly once with the final outcome, and on_feedback (if given) once per feedback message while the request is running.

Parameters

goal	Request content to send.
on_response	Invoked once with the final outcome.
on_feedback	Invoked as feedback arrives, if given.

request_and_wait()

template<typename ActionT>

CapabilityClient< ActionT >::Response request_and_wait	(	const Goal &	goal,
		FeedbackCallback	on_feedback = nullptr,
		std::chrono::milliseconds	timeout = std::chrono::milliseconds(0) )

Asks the capability to do something and blocks the calling thread until the response is ready (or timeout elapses, if positive).

Safe to call from any thread.

Parameters

goal	Request content to send.
on_feedback	Invoked as feedback arrives, if given.
timeout	Maximum time to wait for a response; 0 (the default) waits indefinitely.

Returns

The request's final outcome (Outcome::TIMEOUT if timeout elapsed first).

wait_for_capability() [1/2]

template<typename ActionT>

bool wait_for_capability

(

)

Blocks until the capability is reachable, using the constructor's default_wait_timeout.

Returns

Whether the capability became reachable before the timeout.

wait_for_capability() [2/2]

template<typename ActionT>

bool wait_for_capability

(

std::chrono::milliseconds

timeout

)

Blocks until the capability is reachable, or timeout elapses.

Parameters

timeout

Maximum time to wait.

Returns

Whether the capability became reachable before the timeout.

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The documentation for this class was generated from the following files:

• easyfleet_core/include/easyfleet_core/capability_client.hpp
• easyfleet_core/include/easyfleet_core/detail/capability_client_impl.hpp