Methods in

About Methods

A method is a function with a special receiver argument. The receiver appears in its own argument list between func keyword and the name of the method.

func (receiver type) MethodName(parameters) (returnTypes) {

}

You can only define a method with a receiver whose type is defined in the same package as the method.

type Person struct {
	Name string
}

func (p Person) Greetings() string {
	return fmt.Sprintf("Welcome %s!", p.Name)
}

s := Person{Name: "Bronson"}
fmt.Println(s.Greetings())
// Output: Welcome Bronson!

There are two types of receivers, value receivers, and pointer receivers.

Methods with a value receiver operate on a copy of the value passed to it, meaning that any modification done to the receiver inside the method is not visible to the caller.

You can declare methods with pointer receivers in order to modify the value to which the receiver points. Such modifications are visible to the caller of the method as well.

type rect struct {
	width, height int
}

func (r *rect) squareIt() {
	r.height = r.width
}

r := rect{width: 10, height: 20}
fmt.Printf("Width: %d, Height: %d\n", r.width, r.height)
// Output: Width: 10, Height: 20

r.squareIt()
fmt.Printf("Width: %d, Height: %d\n", r.width, r.height)
// Output: Width: 10, Height: 10

You can find several examples here. Also checkout this short tutorial about methods.

Remember: a method is just a function with a receiver argument.