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

Subject: Re: about CSS BOY
From: "Kasemir, Kay" <kasemirk@ornl.gov>
To: 岳敏 <yuemin@impcas.ac.cn>
Cc: "<tech-talk@aps.anl.gov>" <tech-talk@aps.anl.gov>
Date: Tue, 13 May 2014 12:30:46 +0000
CSS BOY handles the connections for you.
By default, your script will only be called if all PVs are connected.
If you do check the option "Execute anyway even if some PVs are disconnected", then yes, you'll have to handle the case that a PV is disconnected.

You could do this:

if pvs[0].isConnected():
   value = PVUtil.getDouble(pvs[0])

to check if the PV is connected, but
1) That uses the IPV#isConnected() call, and details of the PV implementation might change, so your script will not be portable.
     OK, portability of scripts cannot be guaranteed anyway, but..
2) Race condition: The PV might be connected when you call isConnected(), but then disconnect just before you call getDouble, so you still get the error.


So your best bet might be:

try:
     value = PVUtil.getDouble(pvs[0])
except Exception, e:
    # Well, something failed. Maybe the PV is disconnected?
    pass

-Kay

On May 12, 2014, at 9:49 PM, 岳敏 <yuemin@impcas.ac.cn<mailto:yuemin@impcas.ac.cn>>
 wrote:


      I meet some problem while using CSS. The problem is when I use PVUtil.getDouble() to get the value of some PV, there will be ERROR in BOY console if the PV is disconnected. An example ERROR information is "2014-05-04 17:12:48 ERROR: Error exists in script/CSS/JavaScript/ECR_Print.js Wrapped java.lang.RuntimeException: PV SSC-LINAC:ECR:AGL-BEAM has no value. (script#23)". How can I check the connecting state in javascript code before I use PVUtil.getDouble()?




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 岳 敏 Min Yue

Institute of Modern Physics, Chinese Academy of Sciences
509 Nanchang Road, Lanzhou, 730000, P.R.China

Tel:+86-0931-4969469

Handy: +86-18509316383

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about CSS BOY 岳敏

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