rclcpp::GuardCondition Class Reference

#include <guard_condition.hpp>

Public Member Functions
void	attach_closure_block (detail::HostedBlockBase *block)
Result	clear ()
	GuardCondition ()
	GuardCondition (GuardCondition &&other)
bool	is_triggered () const
bool	is_valid () const
	Check if the guard condition is initialized and valid.
GuardCondition &	operator= (GuardCondition &&other)
Result	trigger ()
	~GuardCondition ()

Friends
class	::rclcpp::Node

Detailed Description

Guard condition for cross-thread signaling.

Guard conditions allow any thread to wake the executor and optionally invoke a callback during spin_once(). The trigger() method is thread-safe and lock-free.

Usage:

void on_signal(void* ctx) { /* handle event *‍/ }
 
rclcpp::GuardCondition guard;
RCLCPP_TRY(node.create_guard_condition(guard, on_signal));
 
// From another thread:
guard.trigger();
// Callback fires on next spin_once()

Constructor & Destructor Documentation

~GuardCondition()

rclcpp::GuardCondition::~GuardCondition ( )

inline

Destructor — releases the guard condition (issue 1667): its executor entry is freed, so spin_once stops polling it and the callback slot goes back to NROS_EXECUTOR_MAX_CBS. Sound because this object is non-copyable and the only holder of the trigger handle; trigger it from another thread only while it is alive.

GuardCondition() [1/2]

rclcpp::GuardCondition::GuardCondition ( GuardCondition &&  other )

inline

GuardCondition() [2/2]

rclcpp::GuardCondition::GuardCondition ( )

inline

Default constructor — creates an uninitialized guard condition. Use Node::create_guard_condition() to initialize.

Member Function Documentation

attach_closure_block()

void rclcpp::GuardCondition::attach_closure_block ( detail::HostedBlockBase *  block )

inline

clear()

Result rclcpp::GuardCondition::clear ( )

inline

Clear the flag without dispatching — the other half of is_triggered(), for a polling owner that has handled the event itself.

is_triggered()

bool rclcpp::GuardCondition::is_triggered ( ) const

inline

Is this guard condition triggered and not yet dispatched?

The RFC-0022 polling tier: a task that owns its own loop and never reaches spin_once still needs to see the flag another thread or an ISR set. rcl and rclcpp have no such reader — a wait set is the only way to observe an rclcpp guard condition — so this is ours, and phase-417 W4.e gave C++ and Rust the reader C already had.

The executor CONSUMES the flag when it dispatches, so this answers "set and not yet dispatched": poll it or take the callback, not both.

is_valid()

bool rclcpp::GuardCondition::is_valid ( ) const

inline

Check if the guard condition is initialized and valid.

operator=()

GuardCondition & rclcpp::GuardCondition::operator= ( GuardCondition &&  other )

inline

trigger()

Result rclcpp::GuardCondition::trigger ( )

inline

Trigger the guard condition (thread-safe, lock-free).

The callback will be invoked on the next spin_once().

Friends And Related Symbol Documentation

::rclcpp::Node

friend class ::rclcpp::Node

friend

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

• include/rclcpp/guard_condition.hpp