Enum QoSHistoryPolicy 

pub enum QoSHistoryPolicy {
    SystemDefault,
    KeepLast,
    KeepAll,
    Unknown,
}

QoS history policy

Variants

SystemDefault

The caller did not state a history policy — the backend picks. Upstream’s RMW_QOS_POLICY_HISTORY_SYSTEM_DEFAULT; lowers to NROS_RMW_HISTORY_SYSTEM_DEFAULT (0) across the C ABI.

See QoSSystemDefaults for how a backend resolves it. Listed first to match rclrs’s enumerator order.

KeepLast

Keep last N messages (where N is defined in QoSProfile)

KeepAll

Keep all messages (up to resource limits)

Unknown

The backend could not determine this policy. Upstream’s RMW_QOS_POLICY_HISTORY_UNKNOWN; lowers to NROS_RMW_HISTORY_UNKNOWN (3) across the C ABI.

An ABSENCE, not a value: it is what a *_get_actual_qos read-back writes for a policy it looked at and cannot report, and it is never a request an application makes. Distinct from SystemDefault, which is “nobody asked, so the middleware chooses” — see QoSProfile::QOS_PROFILE_UNKNOWN.

Trait Implementations

impl Clone for QoSHistoryPolicy

fn clone(&self) -> QoSHistoryPolicy

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Copy for QoSHistoryPolicy

impl Debug for QoSHistoryPolicy

fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error>

Formats the value using the given formatter.

impl Default for QoSHistoryPolicy

fn default() -> QoSHistoryPolicy

Returns the “default value” for a type.

impl Eq for QoSHistoryPolicy

impl PartialEq for QoSHistoryPolicy

fn eq(&self, other: &QoSHistoryPolicy) -> bool

Equality operator ==.

fn ne(&self, other: &Rhs) -> bool

Inequality operator !=.

impl StructuralPartialEq for QoSHistoryPolicy