Method values, part 2

November 8, 2023

Today we finish up the spec’s section on method values, with some very non-surprising bits:

Method values

As with selectors, a reference to a non-interface method with a value receiver using a pointer will automatically dereference that pointer: pt.Mv is equivalent to (*pt).Mv.

As with method calls, a reference to a non-interface method with a pointer receiver using an addressable value will automatically take the address of that value: t.Mp is equivalent to (&t).Mp.

f := t.Mv; f(7)   // like t.Mv(7)
f := pt.Mp; f(7)  // like pt.Mp(7)
f := pt.Mv; f(7)  // like (*pt).Mv(7)
f := t.Mp; f(7)   // like (&t).Mp(7)
f := makeT().Mp   // invalid: result of makeT() is not addressable

Although the examples above use non-interface types, it is also legal to create a method value from a value of interface type.

var i interface { M(int) } = myVal
f := i.M; f(7)  // like i.M(7)

So let’s just explicitly review a complete example:

type Person struct {
	Name string

func (p Person) Hi() { // Value receiver
	fmt.Printf("Hi, %s", p.Name)

func (p *Person) Hello() { // Pointer receiver
	fmt.Printf("Hello, %s", p.Name)

var b = &Person{Name: "Bob"} // b is of type *Person

b.Hi() // equivalent to (*b).Hi

var a = Person{Name: "Alice"} // a is of type Person

a.Hello() // equivalent to (&a).Hello

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

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