ElementOperand QML Type | Qt OPC UA 6.4.1

- Qt 6.4
- Qt OPC UA
- QML Types
- ElementOperand
- Qt 6.4.1 Reference Documentation

# ElementOperand QML Type

The OPC UA ElementOperand type. More...

Import Statement: | import QtOpcUa
Since: | QtOpcUa 5.13

- List of all members, including inherited members

## Properties

- index : int

## Detailed Description

The ElementOperand is defined in OPC-UA part 4, 7.4.4.2. It is used to identify another element in the filter by its index (the first element has the index 0).

This is required to create complex filters, for example to reference the two operands of the AND operation in ((Severity > 500) AND (Message == "TestString")). The first step is to create content filter elements for the two conditions (Severity > 500) and (Message == "TestString"). A third content filter element is required to create an AND combination of the two conditions. It consists of the AND operator and two element operands with the indices of the two conditions created before:

     import QtOpcUa as QtOpcUa

     QtOpcUa.EventFilter {
         select : [ ... ]
         where: [
             QtOpcUa.FilterElement {
                 operator: QtOpcUa.FilterElement.GreaterThan
                 firstOperand: QtOpcUa.SimpleAttributeOperand {
                     browsePath: [
                         QtOpcUa.NodeId {
                             identifier: "Severity"
                             ns: "http://opcfoundation.org/UA/"
                         }
                     ]
                 }
                 secondOperand: QtOpcUa.LiteralOperand {
                     value: 500
                     type: QtOpcUa.Constants.UInt16
                 }
             }
             QtOpcUa.FilterElement {
                 operator: QtOpcUa.FilterElement.Equals
                 firstOperand: QtOpcUa.SimpleAttributeOperand {
                     browsePath: [
                         QtOpcUa.NodeId {
                             identifier: "Message"
                             ns: "http://opcfoundation.org/UA/"
                         }
                     ]
                 }
                 secondOperand: QtOpcUa.LiteralOperand {
                     value: "TestString"
                     type: QtOpcUa.Constants.String
                 }
             }
             QtOpcUa.FilterElement {
                 operator: QtOpcUa.FilterElement.And
                 firstOperand: QtOpcUa.ElementOperand {
                     index: 0
                 }
                 secondOperand: QtOpcUa.ElementOperand {
                     index: 1
                 }
             }
         ]
     }

## Property Documentation

index : int

Index of the filter element that is going to be used as operand.