Software/Inheritance

• Software inheritance

  • Overview

    • Inheritance lets one software object or class acquire behavior from another and specialize it. The relationship may be declared between classes or built from a chain of prototype objects. Software/Inheritance/Class-Based and Software/Inheritance/Prototype-Based explain those mechanisms.
    • Inheritance is also a design claim: the specialized thing should make sense wherever the general thing is expected. Software/Inheritance/Is-A names that claim; Software/Subtyping examines when the substitution is actually valid.

  • Mechanism

    • In Software/Inheritance/Class-Based, a subclass inherits accessible members of a superclass and may add or override behavior. In Software/Inheritance/Prototype-Based, an object delegates property lookup to another object along a prototype chain.
    • A class with more than one parent uses Software/Inheritance/Multiple; Software/Inheritance/Multiple/vs/Single weighs it against single inheritance.
    • Implementation inheritance reuses code. Interface inheritance or subtyping establishes what operations clients may rely on. Sharing code alone does not prove the stronger substitutability claim.

  • Design boundary

    • Inheritance couples a specialization to the behavior and assumptions of its parent. A deep hierarchy can make a change in one class affect distant descendants.
    • Software/Composition assembles behavior from collaborators through a Software/Inheritance/Has-A relationship. It can reuse behavior without claiming that the containing object is a subtype of any collaborator.

  • Sources

    • Inheritance in Java describes subclass members and overriding; MDN's inheritance and prototype chain guide describes delegation through objects.