Methods

Methods in the Go language are similar to functions except they declare a receiver variable (named variable or struct type).

A good way to think of methods are functions that perform actions tied to a specific set of data. Only defined sets of the data in the receiver can access methods.

In the example below, we can see that trying to call the method FullName as a function will result in an error. Likewise, calling the function Test as a method will result in an error as well.

import "fmt"

type User struct {
	First string
	Last  string
}

func main() {
	r := User{First: "Josh", Last: "Silvas"}
	
	// Cannot call a method without a receiver
	// prog.go:16:2: undefined: FullName
	FullName()
	
	// Cannot call a function with a receiver
	// prog.go:20:3: r.Test undefined (type User has no field or method Test)
	r.Test()
}

func (u User) FullName() {
	fmt.Printf("%s %s\n", u.First, u.Last)
}

func Test() {
	fmt.Println("Test String")
}

Go Playground Example

The concept of value and pointer semantics still apply when using method receivers. That is, a method receiver of (u User) will pass a copy of the value of User into the method, whereas a method receiver of (u *User) will pass the address value of User. When sharing data across program boundaries, be mindful of the behavior of receiver value semantics.

Methods initialized with a value receiver can be invoked with both a pointer and a value, however, a method initialized with a pointer receiver can only be invoked with a pointer.

Type	Examples
func (t *Type) Example() {	*type.Example()
func (t Type) Example() {	type.Example() *type.Example()

Example

• Source Example