Promotic

Item - method of the PmaOpcDaClientGroup object

Description:
The method returns object of the PmVar type that represents one variable defined on the "Data" tab.
Syntax:
Object Item(Variant id)
Parameters:
id(Variant) Specifies the variable. The value je:
- Name (String, case sensitive text, for example "d1") or
- Index (Long, zero-based index)
Note:
The PmVar object contains information about the variable (value, name, index, etc.).

If the variable does not exist, then error value (null for JavaScript or Nothing pro VBScript) is returned. The global error of the INFO system is generated. For variable existence testing, it is better to use the ItemEx method.

The method returns only variables (with corresponding data extension) that are created directly in this object (own variables). In fact also other variables from PmaData objects are registered into this object - those that have corresponding data extension configured with path to this object. All data extensions registered in this object can be accessed by the GetVarExtensions method.
Example1:
JavaScriptVBScriptSelect and copy to clipboard

var oOpcGroup = pMe.Pm("/OpcClient/Group1");
var val = oOpcGroup.Item(0).Value;   // Reading the value
oOpcGroup.Item(0).Value = 2;   // Writing the value
Example2:
The Item method returns object of the PmVar type. In this case this object has the following properties Value, TimeStamp and Quality that can be, for example, find out as follows:
JavaScriptVBScriptSelect and copy to clipboard

var oOpcGroup = pMe.Pm("/OpcClient/Group1");
var val = oOpcGroup.Item(0).Value;
var tim = oOpcGroup.Item(0).TimeStamp;
var qual = oOpcGroup.Item(0).Quality;
Example3:
Some OPC servers (for Simatic, Schneider, Bernecker&Reiner ...) can transfer a data array (Array) in one data item (the common limitation is that all data array items must be of the same data type). If it is necessary to receive/send such data as well, then the "Data type" configurator has to be set to Variant data type for the variable (this is disabled in PmRtFree - Free runtime licence).
Example see Data vector transfer
PROMOTIC 9.0.17 SCADA system documentation - MICROSYS, spol. s r.o.

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