D provides support for classes and interfaces like in Java or C++.

Any class type inherits from Object implicitly.

class Foo { } // inherits from Object
class Bar: Foo { } // Bar is a Foo too

Classes in D are generally instantiated on the heap using new:

auto bar = new Bar;

Class objects are always references types and unlike struct aren't copied by value.

Bar bar = foo; // bar points to foo

The garbage collector will make sure the memory is freed when no references to an object exist anymore.


If a member function of a base class is overridden, the keyword override must be used to indicate that. This prevents unintentional overriding of functions.

class Bar: Foo {
    override functionFromFoo() {}

In D, classes can only inherit from one class.

Final and abstract member functions

A function can be marked final in a base class to disallow overriding it. A function can be declared as abstract to force base classes to override it. A whole class can be declared as abstract to make sure that it isn't instantiated. To access the base class, use the special keyword super.


rdmd playground.d