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TUaVariant AsType() missing?

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TUaVariant AsType() missing?

July 27, 2023
16:36, EEST

Guido Niewerth

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Forum Posts: 13

Member Since:
August 23, 2022

Offline

Hello,

I’m trying to read node attributes from nodes an ran across this Delphi snippet from the “UaSampleClientForms.pas” sample:

procedure TUaSampleClientForm.AddSelectedNodesToDataView;
var
DataValue: TUaDataValue;
I: Integer;
TreeNode: TBrowseTreeNode;
begin
for I := 0 to AddressSpaceView.SelectionCount-1 do
begin
if AddressSpaceView.Selections[I] is TBrowseTreeNode then
begin
try
TreeNode := TBrowseTreeNode(AddressSpaceView.Selections[I]);
DataValue := UaClient.ReadAttribute(TreeNode.NodeId, aiNodeClass);
if DataValue.Value.AsType<TUaNodeClass> = ncVariable then
AddNodeToDataView(MonitoredItemView, TreeNode);
except
on E: Exception do
; // Failed – should we notify?
end;
end;
end;
end;

I tried the relavant part in my C++ application:

TUaNodeClass read_node_class( TUaClient* client, TUaNodeId& node_id )
{
TUaDataValue data_value = client->ReadAttribute( node_id, aiNodeClass );

// The following line produces a compiler error
return data_value.Value.AsType<TUaNodeClass>();

// The following line works, because TUaNodeClass is an enumeration.
// But how do I deal with aiNodeId where the TUaVariant holds a TUaNodeId object?
return static_cast<TUaNodeClass>( data_value.Value.AsUInt32 );
}

The compiler error message is:
No member named ‘AsType’ in Prosysopc::Uabase::TUaVariant.

I searched the “ProsysOPC.UaBase.hpp” file for a “AsType” member, but didn’t find anything. There are some conversion functions, but no generic one. I tried ‘AsUInt32’ because TNodeClass is an enumeration and it worked, but I wonder how I can access structure values like TUaNodeId for the aiNodeId attribute?

I am using
– Embarcadero RAD Studio Alexandria 11.2
– Prosys Sentrol OPC UA SDK 7.6.0 for Alexandria 11.x

building for the Win32 platform.

Edit:
How do I post formatted code?

July 28, 2023
10:05, EEST

Ari-Pekka Soikkeli

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Moderators

Forum Posts: 5

Member Since:
February 14, 2022

Offline

Hello,

You can read NodeId values by using the TUaVariant.AsNodeId property:

TUaDataValue DataValue = UaClient->ReadAttribute(SomeNodeId, aiNodeId);
TuaNodeId NodeId = DataValue.Value.AsNodeId;

To read other structured types, you can try TUaVariant.AsStructure:

TUaDataValue DataValue = UaClient->ReadValue(Id_Server_ServerStatus);
TUaStatusCode StatusCode = DataValue.StatusCode;

if (StatusCode.IsGood) {
_di_IUaStructure S = DataValue.Value.AsStructure;
_di_IUaServerStatusDataType ServerStatus;
if (S->Supports(ServerStatus)) {
…

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