Re: pvData Introspection: Change Structure at run time

[Marty Kraimer via Tech-talk <tech-talk at aps.anl.gov>]

Consider using  a union field

https://github.com/epics-base/exampleCPP/blob/master/database/src/exampleDatabase.cpp

Has some examples of how to create a union .

One example is:

static void createVariantUnionArrayRecord(
    PVDatabasePtr const &master,
    string const &recordName)
{
    StructureConstPtr top = fieldCreate->createFieldBuilder()->
         add("timeStamp",standardField->timeStamp()) ->
         addArray("value",fieldCreate->createVariantUnion())->
         createStructure();
    PVStructurePtr pvStructure = pvDataCreate->createPVStructure(top);
    PVRecordPtr pvRecord = PVRecord::create(recordName,pvStructure);
    bool result = master->addRecord(pvRecord);
    if(!result) cout<< "record " << recordName << " not added" << endl;
}

field "value" can be made into any pvType you want. In your case you can make it a structure.
What "value" is can be changed at run time.

On 7/27/20 1:23 PM, Madden, Timothy J. via Tech-talk wrote:

Folks

Most of the interfaces for Structure require a StructureConstPtr data type.

This is a pointer to an immutable structure.

Suppose I wish the structure to change at run time. What do we do? 

Tim Madden

APS