A view is a wrapper type that makes a concrete type appear to be an abstract type.

For example, we might want to view a planet as being a circle.

There may be multiple views of a concrete type, including multiple views as the same abstract type.

• A view is purely gedanken; it does not change the concrete data. Views allow a concrete type to be thought of as another type without being that type.

• A view type has the concrete type as its stored form.

• A view type defines properties that express what the abstract type expects in terms of what the concrete type has.

• Other data of the concrete type are hidden.

• The abstract type is a superclass of the view type.

• Procedures of the abstract type can be inherited and specialized through the view.

Contents    Page-10    Prev    Next    Page+10    Index