Struct vs Class — Living Without Inheritance

For Ruby developers, class is like air. Everything lives inside classes. class User < ApplicationRecord — inherit functionality, mix in modules with include.

Go has no class and no inheritance. Structs define data structures, and methods attach to those structs. That's it.

Ruby's class vs Go's struct

Ruby: class User; attr_accessor :name, :email; end
Go: type User struct { Name string; Email string }

Looks similar but fundamentally different. Ruby's class is a vessel for instance variables, methods, inheritance, mixins. Go's struct is just a bundle of data fields. Methods attach from outside.

No Inheritance — Embedding Instead

class Admin < User is impossible in Go. Instead, embed one struct inside another:

type Admin struct {
    User  // embedding — brings all User fields and methods
    Role string
}

Admin didn't "inherit" User — it "contains" User. admin.Name accesses User's field, and User's methods are callable directly.

Similar to Ruby's include UserModule. But Go's embedding happens at the type level with zero runtime overhead.

No new

Ruby: User.new(name: "kim") — calls initialize. Go has no constructor. User{Name: "kim"} creates a literal, or by convention you write a NewUser("kim") factory function.

private/public by Case

Instead of Ruby's private, protected, public keywords, Go uses the first letter. Uppercase = exported (accessible from outside). Lowercase = package-internal. User.Name is accessible, User.name is not.