Skip to main content
Version: 7.0

OVERRIDE operator

The OVERRIDE operator creates a property that implements the selection of one of the values (polymorphic form).

Syntax​

OVERRIDE expr1, ..., exprN

Description​

The OVERRIDE operator creates a property whose value will be the value of one of the properties specified in the operator. Selection is made among properties with a non-NULL value. If multiple properties are non-NULL, the value of the first of these properties is selected.

Parentheses immediately after OVERRIDE group its first operand; they do not delimit the operand list, so OVERRIDE(expr1, expr2) is not accepted.

Parameters​

  • expr1, ..., exprN

    List of expressions whose values will determine the value of the property.

Examples​

CLASS Group;
markup = DATA NUMERIC[8,2] (Group);

markup = DATA NUMERIC[8,2] (Book);
group = DATA Group (Book);
overMarkup (Book b) = OVERRIDE markup(b), markup(group(b));
// a NULL markup is compared as 0
sameMarkup (Book b1, Book b2) = (OVERRIDE markup(b1), 0) = (OVERRIDE markup(b2), 0);

notNullDate (INTEGER i) = OVERRIDE date(i), 2010_01_01;