Go Inheritance and Polymorphism

Internal

• Go Object Oriented Programming

Overview

Go does not have formal inheritance at language level. Inheritance can be implemented via a combination of struct field embedding and interfaces. The Inheritance section of this article explains how that is done. Once an implicit inheritance structure is put in place, polymorphism is also available.

Inheritance

In its most generic form, inheritance in programming languages is the capability of declaring class hierarchies. A hierarchy includes generic classes, called superclasses, that are inherited by more specific and specialized classes, called subclasses.

The superclasses declare attributes (state) and behavior that are shared with all their descendants. This is a great capability when it comes to code reusability. The generic state and behavior is declared only once, in superclass, and it does not have to be repeated in subclasses. The subclasses also have the capability to declare state and behavior that is particular to them only, and differentiate them from siblings in the hierarchy.

For more general information on inheritance see:

Inheritance

Inheritance as defined above ca be implemented in Go, but without formal support from the language. In other object-oriented languages, there is a formal extends language keyword or other formal syntax that expresses the inheritance relationship between classes. In Java, the inheritance is formally declared with the extends keyword:

class SomeSubclass extends SomeSuperclass {
  ...
}

In Python, we formally declare that a class extends other class with this syntax:

class SomeSubclass(SomeSuperclass):
  ...

State Inheritance

We implement state inheritance by declaring a base struct that contains all the attributes to be shared by inherited types. In this case, in a vehicle hierarchy, the base type is vehicle and it is declared package-private, as it does not need exposure outside the package. An example of an attribute that is common to all members of the hierarchy is speed.

type (
    vehicle struct {
    }
)

 pkg
  └── transportation
       ├── vehicle.go
       ├── car.go
       └── plane.go

Behavior Inheritance

Overriding

Polymorphism

Polymorphism is available in Go, but it is implemented differently than in other object-oriented languages.

For a generic discussion on polymorphism, see:

Object-Oriented Programming | Polymorphism

Overriding

TO DEPLETE

Read and merge into document:

• https://go.dev/doc/faq#Is_Go_an_object-oriented_language