Object-Oriented Programming in GoLang

Object-oriented programming is a programming paradigm which uses the idea of “objects” to represent data and methods. Go does not strictly support object orientation but is a lightweight object Oriented language. Object Oriented Programming in Golang is different from that in other languages like C++ or Java due to factors mentioned below:

1. Struct

Go does not support custom types through classes but structs. Structs in Golang are user-defined types that hold just the state and not the behavior. Structs can be used to represent a complex object comprising more than one key-value pairs. We can add functions to the struct that can add behavior to it as shown below:

Example:

// Golang program to illustrate the
// concept of custom types
package main

import (
    "fmt"
)

// declaring a struct
type Book struct{

    // defining struct variables
    name string
    author string
    pages int
}

// function to print book details
func (book Book) print_details(){

    fmt.Printf("Book %s was written by %s.", book.name, book.author)
    fmt.Printf("\nIt contains %d pages.\n", book.pages)
}

// main function
func main() {

    // declaring a struct instance
    book1 := Book{"Monster Blood", "R.L.Stine", 131}

    // printing details of book1
    book1.print_details()

    // modifying book1 details
    book1.name = "Vampire Breath"
    book1.pages = 162

    // printing modified book1
    book1.print_details()

}

Output:

Book Monster Blood was written by R.L.Stine.
It contains 131 pages.
Book Vampire Breath was written by R.L.Stine.
It contains 162 pages.

2. Encapsulation

It means hiding sensitive data from users. In Go, encapsulation is implemented by capitalizing fields, methods, and functions which makes them public. When the structs, fields, or functions are made public, they are exported on a package level. Some examples of public and private members are:

package gfg

// this function is public as 
// it begins with a capital letter
func Print_this(){
        // implementation
}

// public struct
type Book struct{

        // public field
        Name string
        // private field, only
        // available in gfg package
        author string
}

3. Inheritance

When a class acquires the properties of its superclass then we can say it is inheritance. Here, subclass/child class are the terms used for the class which acquire properties. For this one, one must use a struct to achieve inheritance in Golang. Here, users have to compose using structs to form the other objects.

4. Interfaces

Interfaces are types that have multiple methods. Objects that implement all the methods of the interface automatically implement the interface, i.e., interfaces are satisfied implicitly. By treating objects of different types in a consistent way, as long as they stick to one interface, Golang implements polymorphism.

Example:

// Golang program to illustrate the
// concept of interfaces
package main

import (
    "fmt"
)

// defining an interface
type Sport interface{

    // name of sport method
    sportName() string
}

// declaring a struct
type Human struct{

    // defining struct variables
    name string
    sport string
}

// function to print book details
func (h Human) sportName() string{

    // returning a string value
    return h.name + " plays " + h.sport + "."
}

// main function
func main() {

    // declaring a struct instance
    human1 := Human{"Rahul", "chess"}

    // printing details of human1
    fmt.Println(human1.sportName())

    // declaring another struct instance
    human2 := Human{"Riya", "carrom"}

    // printing details of human2
    fmt.Println(human2.sportName())
}

Output:

Rahul plays chess.
Riya plays carrom.