Using Caché Objects - InterSystems Documentation

The data in Row is the result of executing the query code. Usually, the data in Row is a simple
transformation of a row of the result set. This, however, need not be the case. The code may
perform arbitrary calculations on the result set data and return what it produces in Row. For
example, a call to querynameFetch might return only the first 50 rows of the result set and
convert the names to asterisks for privacy.
8.2.2.3 The Third Argument — The AtEnd Variable
The third argument of a querynameFetch method is of type %Integer, is called AtEnd, and
is passed by reference. If AtEnd equals 1, further calls to querynameFetch will not return
valid rows.
For example, if the ByNameFetch method uses embedded SQL to retrieve data, SQLCODE=100
indicates that no more data is available:
If SQLCODE = 100
{
Set Row = ""
Set AtEnd = 1
}
This is the simplest case, in which reaching the end of the result set causes the method to set
AtEnd to 1. The method's code could alternately perform any processing that its application
requires.
8.2.2.4 Content of the querynameFetch Method
The method code begins by performing tests to determine if it should return any more results.
Usually, if the next fetch should occur, it uses the class query's ROWSPEC specification to
perform processing; it then creates a %List object that is placed in the Row variable. If the
return code from the result set indicates that no more fetches should occur, set the value of
Row to ""; also, set the value of AtEnd to 1.
8.2.2.5 A Sample querynameFetch Signature
Continuing the ByName example, the ByNameFetch method would have the following signature:
ClassMethod ByNameFetch(ByRef qHandle As %Binary,
ByRef Row As %List, ByRef AtEnd As %Integer = 0)
As %Status [ PlaceAfter = ByNameExecute ]
{
// Method code
}
User-Written Class Queries
Using Caché Objects 61