Work with Sets of Instances

An .ifc file may contain several application instances of one type. For such cases, SDAI provides an interface that allows you to:

Search all instances of a specified type.
Manipulate a set of instances of one type, including sequential access to the elements of the set via an iterator object.

To get a set of instances of a specific type, use the sdaiGetEntityExtentBN() function.

To check whether any instance of the specified type is found, call the sdaiGetMemberCount() function. This function returns the quantity of elements in a set.

When you have a non-empty set of instances, you can create an iterator object and then walk through the elements of the set using the following functions:

sdaiCreateIterator() — Create an iterator object (represented with the SdaiIterator datatype).
sdaiBeginning() — Move to the first element of the set.
sdaiNext() — Get access to the next element of the set.
sdaiGetAggrByIterator() — Get access to the current element of the set.

The following code fragment illustrates how to find all IFCBSPLINECURVEWITHKNOTS instances in a model and iterate through the set of found instances.


SdaiString entityName = "IFCBSPLINECURVEWITHKNOTS";
SdaiSet bsplineInstanceSet = sdaiGetEntityExtentBN(model, entityName);

if (!sdaiGetMemberCount(bsplineInstanceSet))
  return;

SdaiIterator bsplineIterator = sdaiCreateIterator(bsplineInstanceSet);
if (sdaiErrorQuery() != sdaiNO_ERR)
  return;

for (sdaiBeginning(bsplineIterator); sdaiNext(bsplineIterator);)
{
  SdaiInstance instance = NULL;
  sdaiGetAggrByIterator(bsplineIterator, sdaiINSTANCE, &instance);

  SdaiInteger instanceId = _sdaiGetEntityId(instance);

  if (sdaiErrorQuery() != sdaiNO_ERR)
    return;
}

See Also