DDS::InstanceStateKind Struct Reference

Indicates if the samples are from a live DDS::DataWriter or not. More...

#include <managed_subscription.h>

Properties
static InstanceStateKind	ALIVE_INSTANCE_STATE [get]
	Instance is currently in existence. More...
static InstanceStateKind	NOT_ALIVE_DISPOSED_INSTANCE_STATE [get]
	Not alive disposed instance. The instance has been disposed by a DataWriter. More...
static InstanceStateKind	NOT_ALIVE_NO_WRITERS_INSTANCE_STATE [get]
	Not alive no writers for instance. None of the DDS::DataWriter objects that are currently alive (according to the LIVELINESS) are writing the instance. More...
static InstanceStateKind	ANY_INSTANCE_STATE [get]
	Any instance state ALIVE_INSTANCE_STATE | NOT_ALIVE_DISPOSED_INSTANCE_STATE | NOT_ALIVE_NO_WRITERS_INSTANCE_STATE. More...
static InstanceStateKind	NOT_ALIVE_INSTANCE_STATE [get]
	Not alive instance state NOT_ALIVE_DISPOSED_INSTANCE_STATE | NOT_ALIVE_NO_WRITERS_INSTANCE_STATE. More...

Detailed Description

Indicates if the samples are from a live DDS::DataWriter or not.

For each instance, the middleware internally maintains an instance state. The instance state can be:

• DDS::InstanceStateKind::ALIVE_INSTANCE_STATE indicates that (a) samples have been received for the instance, (b) there are live DDS::DataWriter entities writing the instance, and (c) the instance has not been explicitly disposed (or else more samples have been received after it was disposed).

• DDS::InstanceStateKind::NOT_ALIVE_DISPOSED_INSTANCE_STATE indicates the instance was explicitly disposed by a DDS::DataWriter by means of the dispose operation.

• DDS::InstanceStateKind::NOT_ALIVE_NO_WRITERS_INSTANCE_STATE indicates the instance has been declared as not-alive by the DDS::DataReader because it detected that there are no live DDS::DataWriter entities writing that instance.

The precise behavior events that cause the instance state to change depends on the setting of the OWNERSHIP QoS:

• If OWNERSHIP is set to DDS::OwnershipQosPolicyKind::EXCLUSIVE_OWNERSHIP_QOS, then the instance state becomes DDS::InstanceStateKind::NOT_ALIVE_DISPOSED_INSTANCE_STATE only if the DDS::DataWriter that "owns" the instance explicitly disposes it. The instance state becomes DDS::InstanceStateKind::ALIVE_INSTANCE_STATE again only if the DDS::DataWriter that owns the instance writes it.

• If OWNERSHIP is set to DDS::OwnershipQosPolicyKind::SHARED_OWNERSHIP_QOS, then the instance state becomes DDS::InstanceStateKind::NOT_ALIVE_DISPOSED_INSTANCE_STATE if any DDS::DataWriter explicitly disposes the instance. The instance state becomes DDS::InstanceStateKind::ALIVE_INSTANCE_STATE as soon as any DDS::DataWriter writes the instance again.

The instance state available in the DDS::SampleInfo is a snapshot of the instance state of the instance at the time the collection was obtained (i.e. at the time read or take was called). The instance state is therefore the same for all samples in the returned collection that refer to the same instance.

Property Documentation

ALIVE_INSTANCE_STATE

InstanceStateKind DDS::InstanceStateKind::ALIVE_INSTANCE_STATE

staticget

Instance is currently in existence.

NOT_ALIVE_DISPOSED_INSTANCE_STATE

InstanceStateKind DDS::InstanceStateKind::NOT_ALIVE_DISPOSED_INSTANCE_STATE

staticget

Not alive disposed instance. The instance has been disposed by a DataWriter.

NOT_ALIVE_NO_WRITERS_INSTANCE_STATE

InstanceStateKind DDS::InstanceStateKind::NOT_ALIVE_NO_WRITERS_INSTANCE_STATE

staticget

Not alive no writers for instance. None of the DDS::DataWriter objects that are currently alive (according to the LIVELINESS) are writing the instance.