Now that we’ve covered function declarations, let’s discuss the more nuanced topic of method declarations, which can be thought of as special case of of function declarations.

Method declarations

A method is a function with a receiver. A method declaration binds an identifier, the method name, to a method, and associates the method with the receiver’s base type.

MethodDecl = "func" Receiver MethodName Signature [ FunctionBody ] .
Receiver   = Parameters .

Before we dive into the details and nuances over the next few days, let’s summarize with a simple example:

type Person struct {
	Name string
}

func (p *Person) Hello() {
	fmt.Printf("Hello, %s\n", p.Name)
}

Here Hello is declared as a method of *Person. This is evident by the fact that it has a receiver (the function argument that preceeds the name of the function).

As an aside, there are two ways to call a method in Go. The most natural/obvoius one, you likely can guess, or have seen:

var p Person{Name: "Bob"}

p.Hello() // Call the Hello() method on the p variable

The other, which you’ll probably never need, but also exists, is to pass the receiver as a direct argument to the fully qualified method name. This doesn’t require defining a variable first:

(*Person).Hello(&Person{Name: "Alice"})

See it in the playground

Quotes from The Go Programming Language Specification Version of August 2, 2023