Public Member Functions
|virtual const char *
|Get the expression for this DDSMultiTopic.
|get_expression_parameters (DDS_StringSeq ¶meters)=0
|Get the expression parameters.
|set_expression_parameters (const DDS_StringSeq ¶meters)=0
Static Public Member Functions
|static DDSMultiTopic *
|narrow (DDSTopicDescription *topic_description)
|Narrow the given DDSTopicDescription pointer to a DDSMultiTopic pointer.
DDSMultiTopic allows a more sophisticated subscription that can select and combine data received from multiple topics into a single resulting type (specified by the inherited
type_name). The data will then be filtered (selection) and possibly re-arranged (aggregation/projection) according to a
subscription_expression with parameters
subscription_expression is a string that identifies the selection and re-arrangement of data from the associated topics. It is similar to an SQL statement where the SELECT part provides the fields to be kept, the FROM part provides the names of the topics that are searched for those fields, and the WHERE clause gives the content filter. The Topics combined may have different types but they are restricted in that the type of the fields used for the NATURAL JOIN operation must be the same.
expression_parameters attribute is a sequence of strings that give values to the 'parameters' (i.e. "%n" tokens) in the
subscription_expression. The number of supplied parameters must fit with the requested values in the
subscription_expression (i.e. the number of n tokens).
DDSDataReader entities associated with a DDSMultiTopic may access instances that are "constructed" at the DDSDataReader side from the instances written by multiple DDSDataWriter entities. The DDSMultiTopic access instance will begin to exist as soon as all the constituting DDSTopic instances are in existence. The
instance_state is computed from the corresponding states of the constituting instances:
view_state of the DDSMultiTopic instance is
DDS_NEW_VIEW_STATE if at least one of the constituting instances has
view_state = DDS_NEW_VIEW_STATE. Otherwise, it will be DDS_NOT_NEW_VIEW_STATE.
instance_state of the DDSMultiTopic instance is DDS_ALIVE_INSTANCE_STATE if the
instance_state of all the constituting DDSTopic instances is DDS_ALIVE_INSTANCE_STATE. It is DDS_NOT_ALIVE_DISPOSED_INSTANCE_STATE if at least one of the constituting DDSTopic instances is DDS_NOT_ALIVE_DISPOSED_INSTANCE_STATE. Otherwise, it is DDS_NOT_ALIVE_NO_WRITERS_INSTANCE_STATE.
|virtual const char* DDSMultiTopic::get_subscription_expression
|virtual DDS_ReturnCode_t DDSMultiTopic::get_expression_parameters
Get the expression parameters.
The expressions syntax is described in the DDS specification.
parameters is either specified on the last successful call to DDSMultiTopic::set_expression_parameters, or if DDSMultiTopic::set_expression_parameters was never called, the
parameters specified when the DDSMultiTopic was created.
|<<inout>> Fill in this sequence with the expression parameters. The memory for the strings in this sequence is managed according to the conventions described in Conventions. In particular, be careful to avoid a situation in which RTI Data Distribution Service allocates a string on your behalf and you then reuse that string in such a way that RTI Data Distribution Service believes it to have more memory allocated to it than it actually does.
|virtual DDS_ReturnCode_t DDSMultiTopic::set_expression_parameters
|const DDS_StringSeq &