Inheritance and composition

Inheritance allows us to extend an object to specialized versions of some abstract type. In Dart, by simply declaring a class, we are already extending the Object type implicitly. The following also applies:

• Dart permits single direct inheritance.
• Dart has special support for mixins, which can be used to extend class functionalities without direct inheritance, simulating multiple inheritances, and reusing code.
• Dart does not contain a final class directive like other languages, that is, a class can always be extended (have children).