object

For object like types, Go has the struct type:

object.go

type Person struct {
    Name string
    Age  int
}
func main() {
    p := Person{Name: "John", Age: 30}
    fmt.Println(p.Name) // John
    fmt.Println(p.Age)  // 30
}

Like with normal variables, each field in a struct is initialized to its zero value if not explicitly set:

object.go

type Person struct {
    Name string
    Age  int
}
func main() {
    p := Person{} // No fields set
    fmt.Println(p.Name) // "" - zero value of string
    fmt.Println(p.Age)  // 0 - zero value of int
}

Methods

Structs can have methods associated with them, similar to classes in JavaScript/TypeScript:

object.go

type Person struct {
    Name string
    Age  int
}
func (p Person) Greet() string {
    return "Hello, " + p.Name
}
func main() {
    p := Person{Name: "John", Age: 30}
    fmt.Println(p.Greet()) // Hello, John
}

Caution

If you want to modify the struct, you need to use a pointer receiver!

object.go

type Person struct {
    Name string
    Age  int
}
func (p *Person) Birthday() {
    p.Age++
}

func main() {
    p := Person{Name: "John", Age: 30}
    p.Birthday()
    fmt.Println(p.Age) // 31
}

Note the * before Person in the method signature. This indicates that p is a pointer to a Person struct. This allows you to modify the original struct when calling the method.

Without it, Go would create a copy of the struct and any modifications would not affect the original struct.

Caution

The following code will compile and run just fine but won’t modify the original struct:

object.go

type Person struct {
    Name string
    Age  int
}
func (p Person) Birthday() {
    p.Age++
}
func main() {
    p := Person{Name: "John", Age: 30}
    p.Birthday()
    fmt.Println(p.Age) // 30
}

In this case, the Birthday method receives a copy of p, increments the age of the copy, and then discards it. The original p remains unchanged.