Subject: |
Re: dataAccess V4 Ca client propertyId questions |
From: |
Marty Kraimer <[email protected]> |
To: |
EPICS Core Talk <[email protected]> |
Date: |
Wed, 29 Jun 2005 08:55:13 -0500 |
On Jun 27, 2005, at 2:03 PM, Kay-Uwe Kasemir wrote:
On Jun 27, 2005, at 12:02, Marty Kraimer wrote:
Can it ask for a list of properrtyIds?
...
Given a list of propertyIds how does it obtain the information
associated with each id?
The V4 "client user interface" suggests these in the "DataAccess"
interface:
list<string> getProperties() Get a list of all the properties
type_info getType(string property)
string getAsString(string property)
Ca accepts a request to get data associated with a propertyId.
Instead of putting it into a caller provided container via the caller
supplied propertyCatalog, CA would make the data available via the
caller supplied dataViewer.
We pretend that the CA client library & data access doesn't hold the
data,
but only presents an interface for the user to copy the data into a
user-provided container.
Well, while you use dataAccess, the CA client library actually holds
the data in some temporary network buffer.
So you don't need a container at all if you only want to get a list
of all the properties & types.
Does the proposed CA V4 interface allow this?
Yes, Jeff proposes a channel::createAllPropertiesReadRequest.
Does that cover your idea for a simply 'probe'- type application?
createAllPropertiesReadRequest
...
foreach p ( da->getProperties() )
{
display da->getType(p), da->getAsString(p)
}
... or would you also like to see a request that only
gets the properties and types, without fetching any actual values?
-Kay
In the above type_info is mentioned.
What is it?
It says that it is part of dataAccess not just part of CA.
But
On Jun 28, 2005, at 8:28 AM, Ralph Lange wrote:
I don't understand. The main feature of dataAccess *is* an
introspection interface. Always has been. From day one for the last
five years. The traverse() methods have been there for ages.
So: By supporting dataAccess I am supporting an introspection
interface. Of course.
This does not seem to imply that a type_info is how introspection is
supported.
I take it to mean that the following is done when a CA client
introspects
CA provides a propertyCatalog.
The client implements a propertyViewer which has all the overloaded
reveal methods. By seeing which overloadsed method is called it can
determine what type associated with the propertyId.
I am confused.
Marty
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- Re: dataAccess V4 Ca client propertyId questions Kay-Uwe Kasemir
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