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Can not set Value if it is Null

Questions regarding the use of the UaExpert.

Can not set Value if it is Null

Postby profanter » 02 Aug 2019, 13:26

Hi,
UaExpert is not able to set variable values if the value is not yet set.

Please check this image:
Image

(I could not add an attachment, I get the error "Sorry, the board attachment quota has been reached.")

It shows that Value->Value = Null, but DataType is set to Boolean.
In the DataAccessView the Datatype is wrongly showsn as Null.

Normally it should be possible to set the value by double-clicking it, but in this case, if Value=Null, nothing happens.

Is this a bug or expected behaviour?

UaExpert Version: 1.5.0 319

The issue can easily be reproduced using the open62541 Stack `server_testnodeset` example (https://github.com/open62541/open62541/ ... tnodeset.c) and then add `Int32_scalar_noInit_ValueRank=-2` to the data view.


Thanks
Stefan
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Re: Can not set Value if it is Null

Postby Support Team » 15 Aug 2019, 15:58

Hello Stefan,

this is expected behavior. Typically when a node is being subscribed it already has a value (and a value always has a type). The DAView is obtaining the values datatype form the received value (received during first update). However if your node has no value the UaExpert will assume its type is "NULL", because it never has received a value. Reading the attribute (as suggested by you) makes no sense, because the node can change the valued datatype during runtime, so besides creating unnessecary load (by manually reading data type attribute), the datatype may still be different when being used. And of course you can write the value, just need to use the attribute window for writing.

In any case you should take a close look at the Server, why is it having nodes that have no value? That makes not much sense.
Best regards
Unified Automation Support Team
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