True and False (SelectionCriterion functions)

Create selection expression that returns any item or no items (SelectionCriterion class)

These shared methods take no parameters and create a new SelectionCriterion object. A True criterion returns true for any collection item; a False criterion returns false for any collection item.

True and False thus provide the equivalent of an empty SelectionCriterion, and they substitute for a New constructor in the SelectionCiterion class.

The collection searching method that makes use of a SelectionCriterion specifies:

• Whether to return the first item or item number or all items that satisfy the selection criterion.
• Where in the collection to begin searching.

Syntax

%selectionCriterion = [%(SelectionCriterion For itemType):]True

%selectionCriterion = [%(SelectionCriterion For itemType):]False

Syntax terms

%selectionCriterion	A SelectionCriterion object variable to contain the new object instance.
%(SelectionCriterion For itemtype)	This optional specification of the class in parentheses indicates that the method is shared and does not operate on a specific instance. If you use this option, however, you must include the collection item type to which the selection expression will be applied, like this: %(selectionCriterion For itemtype):

Usage Notes

• True and False exist to simplify dynamic SelectionCriterion applications. If you are dynamically generating a SelectionCriterion, under some conditions you may want the criterion to select all objects or to select no objects. In addition, if you are building a SelectionCriterion by using Or in conditions, it might be useful to start out with a False SelectionCriterion:

  %sel = False if <somecondition1> then %sel = Or(%sel, Eq(foo, 'A')) end if if <somecondition2> then %sel = Or(%sel, Eq(foo, 'B')) end if if <somecondition3> then %sel = Or(%sel, Eq(foo, 'C')) end if

  Similarly, if building a SelectionCriterion by using And in conditions, it might be useful to start out with a True SelectionCriterion.

Examples

The following statements are equivalent:

%sel = and(ge(this, 22), true) %sel = ge(this, 22)

See also

SelectionCriterion class	List of SelectionCriterion methods	SelectionCriterion methods syntax
Notation conventions for methods