ItemNotFound class: Difference between revisions
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Revision as of 21:26, 16 January 2011
An ItemNotFound exception indicates that a collection object search located no collection items that satisfy the selection criterion specified in the collection method that invoked the search. There are several methods for searching a collection, but only those that return a single found item produce an ItemNotFound exception.
This exception class has no properties. It is simply a notification that a valid search found no items that met the selection criterion.
The class's only method is the New constructor, which you would typically use with a User Language Throw statement to produce an ItemNotFound exception:
throw %(itemNotFound):new
When working with the collection searching methods, remember that an exception is thrown only if there is a catcher for the exception. For example, if you expect one or no matches from your search, you might specify a block like the following:
try %terminationInfo = - %terminationList:findNextItem (eq(custId, %custid) ... process the termination info catch itemNotFound end try
On the other hand, if you always expect a match, you might want a program crash to result if you are wrong about the match, so you could leave out a Try/Catch.
The Try/Catch approach is slightly more efficient than a test for a zero result. Try generates no quads other than the branch around the catch block if the search succeeds. And in fact, you could put a Try around a loop and use the ItemNotFound exception to exit the loop:
%i = 0 try repeat forever %i = %colla:findNextItemNumber(<criterion>), start=%i) %obj = %colla(%i) ... process the object end repeat catch itemNotFound end try
The methods in this class are listed at "List of ItemNotFound methods".
The ItemNotFound class is available as of Sirius Mods version 7.6.