Defines an EventFilter for a monitored item. 更多...
导入语句: | import QtOpcUa |
Since: | QtOpcUa 5.13 |
An event filter is required for monitoring events on the server. It consists of
select
clauses and a
where
子句。
select
clauses are used to specify the data the user wants to receive when an event occurs. It consists of
SimpleAttributeOperand
simple attribute operands which select attributes of child nodes of an event type, for example the value attribute of the "Message" property of BaseEventType.
where
clause is used to restrict the reported events by matching against certain criteria. Several operators and four different operand types allow filtering based on the values of the attributes of the child nodes of an event type.
The select clause consists of an array of SimpleAttributeOperand . The where clause consists of an array of SimpleAttributeOperand , LiteralOperand , ElementOperand or AttributeOperand .
The following EventFilter tells the server to report the value of the "Message" field for events that have a "Severity" field with value >= 500:
import QtOpcUa 5.13 as QtOpcUa QtOpcUa.Node { ... eventFilter: QtOpcUa.EventFilter { select: [ QtOpcUa.SimpleAttributeOperand { browsePath: [ QtOpcUa.NodeId { identifier: "Severity" ns: "http://opcfoundation.org/UA/" } ] }, QtOpcUa.SimpleAttributeOperand { browsePath: [ QtOpcUa.NodeId { identifier: "Message" ns: "http://opcfoundation.org/UA/" } ] } ] where: [ QtOpcUa.FilterElement { operator: QtOpcUa.FilterElement.GreaterThanOrEqual firstOperand: QtOpcUa.SimpleAttributeOperand { browsePath: [ QtOpcUa.NodeId { identifier: "Severity" ns: "http://opcfoundation.org/UA/" } ] } secondOperand: QtOpcUa.LiteralOperand { value: 700 type: QtOpcUa.Constants.UInt16 } } ] } }
For a more complex example with two conditions, see QOpcUaElementOperand .
另请参阅 FilterElement .
select : list < SimpleAttributeOperand > |
Selected event fields that shall be included when a new event is reported.
where : list < FilterElement > |
Content filter used to restrict the reported events to events matching certain criteria.