Software/Inheritance/Has-A

• Has-a relationship

  • Overview

    • A has-a relationship says that one object contains, owns, or uses another as a collaborator. A Bicycle has a Wheel; it can delegate wheel-related work to that part without becoming a kind of wheel.

  • In software

    • Software/Composition assembles an object from parts with distinct responsibilities. The containing object can expose a stable interface while changing or replacing a collaborator behind it.
    • Ownership is not implied by the phrase alone: a field may own its component, share it, or merely hold a reference. Lifetime and replacement rules belong to the particular design.

  • Distinction

    • Software/Inheritance/Is-A makes a substitutability claim about a specialized kind. A has-a link says how behavior is assembled, not that the containing object is a subtype of its component; Software/Subtyping explains that separate relationship.