Go Receiver Function like Class Method

@ Go

Go Receiver Function

The first time you see a Go Receiver Function, you might wonder what this strange syntax is, with parameters accepted before the function name?

type User struct {
  name string
}


// receiver function
func (u User) Greet() {
  fmt.Println("Hello, my name is", u.name)
}


func main() {
  u := User{name: "Riceball"}
  u.Greet()
}

Go language advocates for “Composition over inheritance” and pursues code simplicity to avoid the complexities brought by class-based OOP. Therefore, Go does not provide an inheritance mechanism directly but achieves a similar OOP pattern through the following three core elements:

  • Structs: Used to define the structure of data.
  • Receiver Functions (Method): Used to define associated methods for custom types (including structs, custom types based on built-in types, etc.).
  • Interfaces: Used to implement polymorphism.

Examples in Other Languages

JavaScript

const user = {
  name: "Riceball",
  greet() {
    console.log("Hello, my name is", this.name)
  }
}


user.greet()

Java

class User {
    private String name;


    public User(String name) {
        this.name = name;
    }


    public void greet() {
        System.out.println("Hello, my name is " + this.name);
    }
}


public class Main {
    public static void main(String[] args) {
        User u = new User("Riceball");
        u.greet(); // Hello, my name is Riceball
    }
}

Summary

The Go Receiver Function is essentially still an independent function; it just uses special syntax to “bind” the function to a specific type, allowing it to be called in an object-oriented style. This design cleverly balances the encapsulation of object-oriented programming and the simplicity that Go pursues.

However, compared to person.greet("Hi"), I still prefer the pure function way of thinking, greet("Hi", person).

  • One is the function is part of the data.
  • One is the function and data are independent of each other.

In the mindset of writing Go, it’s fascinating how both ways intertwine.

Further Reading