Expressions and Type Inheritance

You can reference a parent class or a derived class in the data-member access path of an expression.

For example, let us assume the following Server model:

B inherits from A

C has a unary relation r on A

The following specification is correct:

subscribe origin B:

represent Table t:

...;

subscribe C:

represent Row row:

Ref<Table> table=r.B->table;

When expression r.B->t is evaluated, the following happens:

First the target of the relation r is accessed. If it exists, it is safely downcast to the type B (using the static member function B::Narrow).

If the downcast succeeds, the reference of the table associated with the B object, if any, is returned.

In other cases, a null reference is returned.

Version 5.8