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Version: 5.x

<- WHEN statement

The <- WHEN statement creates a calculated event.

Syntax​

propertyId(param1, ..., paramN) <- valueExpr WHEN eventExpr;

Description​

The <- WHEN statement creates a calculated event for the property specified on the left side of the statement. This operator can declare its own local parameters when specifying the property whose value will change. These parameters can then be used in expressions of the condition and value to which the property will change.

Only one calculated event can be defined for a property.

Parameters​

  • propertyId

    ID of the property whose value will be changed when the event occurs.

  • param1, ..., paramN

    Typed parameters properties whose value will be changed when the event occurs. The number of these parameters must be equal to the number of parameters of the property being changed.

  • valueExpr

    The expression to whose value the property value must be changed.

  • eventExpr

    An expression whose value is a condition for the generated event.

Examples​

// when adding a client, by default, give him the specified discount
defaultDiscount = DATA NUMERIC[6,2] ();
discount = DATA NUMERIC[6,2] (Customer);
discount(Customer c) <- defaultDiscount() WHEN SET(c IS Customer);

quantity = DATA NUMERIC[10,2] (OrderDetail);
price = DATA NUMERIC[10,2] (OrderDetail);
sum = DATA NUMERIC[10,2] (OrderDetail);

sum(OrderDetail d) <- quantity(d) * price(d) WHEN CHANGED(quantity(d)) OR CHANGED(price(d));