Determine the cardinality of a collection

The DataBlade® API provides the mi_collection_card() function for obtaining the number of elements in a collection (its cardinality).

The following code fragment uses the mi_collection_card() function to perform separate actions based on whether a collection is NULL or has elements (possibly 0 elements): 
MI_COLLECTION *collp;
mi_integer cardinality;
mi_boolean isnull;


/* Attach collp to a collection */


cardinality = mi_collection_card(collp, &isnull);
if ( isnull == MI_TRUE )
   {
   mi_db_error_raise(conn, MI_MESSAGE, "Warning: Collection is NULL.");
   }
else
   {
   if ( cardinality > 0 )
      {
      /*  Open collection and perform action on individual elements */
      }
   }