Editing D (programming language) (section)

====Object-oriented====
Object-oriented programming in D is based on a single [[Inheritance (object-oriented programming)|inheritance]] hierarchy, with all classes derived from class Object. D does not support multiple inheritance; instead, it uses Java-style [[interface (Java)|interfaces]], which are comparable to C++'s pure abstract classes, and [[mixin]]s, which separate common functionality from the inheritance hierarchy. D also allows the defining of static and final (non-virtual) methods in interfaces.

Interfaces and inheritance in D support [[Covariance and contravariance (computer science)|covariant types]] for return types of overridden methods.

D supports type forwarding, as well as optional custom [[dynamic dispatch]].

Classes (and interfaces) in D can contain [[Class invariant|invariants]] which are automatically checked before and after entry to public methods, in accordance with the [[design by contract]] methodology.

Many aspects of classes (and structs) can be [[Type introspection|introspected]] automatically at compile time (a form of [[reflective programming]] (reflection) using <code>type traits</code>) and at run time (RTTI / <code>TypeInfo</code>), to facilitate generic code or automatic code generation (usually using compile-time techniques).