Re: Get the type of a PV in C++ API

["Veseli, Sinisa via Tech-talk" <tech-talk at aps.anl.gov>]

Hi,

PvaPy C++ code still uses the original APIs, so perhaps this example helps:

https://github.com/epics-base/pvaPy/blob/master/src/pvaccess/PyPvDataUtility.cpp#L410

Sinisa

--

Siniša Veseli

Scientific Software Engineering & Data Management

Advanced Photon Source

Argonne National Laboratory

sveseli at anl.gov

(630)252-9182

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From: Tech-talk <tech-talk-bounces at aps.anl.gov> on behalf of Eusebio Naif Al-Soliman Fuentes via Tech-talk <tech-talk at aps.anl.gov>
Sent: Friday, November 3, 2023 4:39 AM
To: Ralph Lange <ralph.lange at gmx.de>
Cc: Tech Talk <tech-talk at aps.anl.gov>
Subject: Re: Get the type of a PV in C++ API

 

Hello Ralph.

 

First of all, thanks for your reply. I know the existence of PVXS library and I have already used it succesfully on my project. The problem is that, at the moment, I've noticed that it's slow for our project and I'm looking for a solution with the first-generation API.

 

It could also be an error in my code, what I'm doing at the moment is this:

 

pvxs::Value reply = ctxt.get(var_name_str).exec()->wait();

pvxs::TypeCode type_var = reply["value"].type();

 

Thanks, Eusebio.

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Saludos/Best regards

University of Granada  

Eusebio Naif Al-Soliman Fuentes
MSc. Data Science and Computer Engineering

eunaif at correo.ugr.es

El 2023-11-02 15:01, Ralph Lange via Tech-talk escribió:

Not an answer to your question, but...

That library you are using is part of the first generation of user-facing
libraries.
Meanwhile, there's a second generation (both for C++ and Java) with more
modern and language-specific API designs. Better usability, easier to work
with, better performance.
These second-generation libraries are stable; they will be replacing the
older generation.
For your use case: The C++ second-generation library is called PVXS -
https://urldefense.com/v3/__https://mdavidsaver.github.io/pvxs/__;!!D9dNQwwGXtA!QvJCJFvFjdyKLmOVaaoqQ-_7p7M-QOxB1j1874UChwdwp4EIbx70WhtalgizLcJWAVZmwNrzC6XHFczTXw-W7sCO$

For any new development - please start there. It will save you from
migrating your application at some point in the near future.

Cheers,
~Ralph


On Thu, 2 Nov 2023 at 12:46, Eusebio Naif Al-Soliman Fuentes via Tech-talk <
tech-talk at aps.anl.gov> wrote:

Hello everybody.

I have a small question. In the pvaClient library for C++ (
https://urldefense.com/v3/__https://docs.epics-controls.org/projects/pvaclient-cpp/en/latest/__;!!D9dNQwwGXtA!QvJCJFvFjdyKLmOVaaoqQ-_7p7M-QOxB1j1874UChwdwp4EIbx70WhtalgizLcJWAVZmwNrzC6XHFczTX6fDGW9p$ ) there
are many examples to get the value and other fields of a PV.

However, in order to get the value as a double, like in this example
https://urldefense.com/v3/__https://github.com/epics-rip/exampleCPP/blob/master/exampleClient/src/examplePvaClientGet.cpp__;!!D9dNQwwGXtA!QvJCJFvFjdyKLmOVaaoqQ-_7p7M-QOxB1j1874UChwdwp4EIbx70WhtalgizLcJWAVZmwNrzC6XHFczTXz1KPekp$ ,
you have to previously know that the PV value is a double. Is there any
method to get the type (int, long, double...) of the value field? Something
like ->getType().

Thanks in advance.
--

Saludos/Best regards

*University of Granada  *

Eusebio Naif Al-Soliman Fuentes
*MSc. Data Science and Computer Engineering*

eunaif at correo.ugr.es