Ada Programming/Attributes/'Tag
Description
editX'Tag is an Ada attribute where X is any tagged type. This attribute returns a value of the private type Ada.Tags.Tag which identifies the tagged type.
This attribute is useful to check for membership of a type in a class hierarchy. It can also be used if it is known the type is in a class hierarchy and type-specific processing must take place.
Example
editRef : My_Tagged_Type_Reference; ...if
Ref.all
in
My_Tagged_Type'Classthen
-- The object pointed at by Ref is in class hierarchy that is rooted at My_Tagged_Type.if
Ref.all
'Tag = My_Tagged_Type'Tagthen
-- Object is of type My_Tagged_Type.else
-- Object is of some other type in the hierarchy.end
if
;else
-- Object is not in the class hierarchy rooted at My_Tagged_Type (it might be of a progenitor type though).end
if
;