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<== Date ==> <== Thread ==>

Subject: Re: Get sub field of Union
From: Michael Davidsaver via Core-talk <core-talk@aps.anl.gov>
To: "Shen, Guobao" <gshen@anl.gov>
Cc: "core-talk@aps.anl.gov" <core-talk@aps.anl.gov>
Date: Thu, 21 Mar 2019 11:19:05 -0700
On 3/21/19 8:43 AM, Shen, Guobao via Core-talk wrote:
> Hi Core member,
> 
> Does anyone have experienced to read sub field of a Union structure?

What you are showing looks like a discriminating/tagged union.
This is quite different to having a union containing a structure,
which is maybe what you expect?


> For example, I have a record:
> 
> $ pvinfo Test:Data
> 
> …
> 
> structure
> 
>     uint ArrayId
> 
>     double[] Time
> 
>     union value
> 
>         float[] data1
> 
>         double[] data2
> 
>  
> 
> If I use
> 
> $ pvget -r value Test:Data
> 
> Test:Data
> 
> structure
> 
>     union value
> 
>         float[]  [-0.034794,-0.0417011, …]
> 
>  
> 
> But if I do it with:
> 
> $ pvget -r value.data1 Test:Data
> 
>  
> 
> I got an error on my client like
> 
> [Test: Data] failed to create channel get: Status [type=FATAL, message=std::bad_alloc]
> 
>  
> 
> Is that a right way to use it for union?
> 
>  
> 
> Thanks,
> 
> Guobao
> 


Replies:
Re: Get sub field of Union Shen, Guobao via Core-talk
References:
Get sub field of Union Shen, Guobao via Core-talk

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