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Go Function Method

Last Updated : July 21, 2025

In Go, methods are functions that are associated with a specific type. Unlike regular functions, methods have a receiver, which allows the function to operate on values of a particular type.

What is a Method in Go?

A method is a function with a special receiver argument. This receiver can either be a value type or a pointer type. Methods let you define behavior that belongs to a specific type.

Syntax

Here is the syntax to define a method:

// Syntax of method
func (receiver Type) methodName(params) returnType {
    // method body
}

Defining Methods on Structs

You can associate a method with a struct type. This is useful to define behaviors specific to the struct's data.

Example

This example shows how to define and call methods on a struct:

package main
import "fmt"

type Rectangle struct {
    width  float64
    height float64
}

// Method with value receiver
func (r Rectangle) area() float64 {
    return r.width * r.height
}

// Method with pointer receiver
func (r *Rectangle) scale(factor float64) {
    r.width *= factor
    r.height *= factor
}

func main() {
    rect := Rectangle{width: 4, height: 3}
    fmt.Println("Area before scaling:", rect.area())

    rect.scale(2)
    fmt.Println("Area after scaling:", rect.area())
}

When you run the above code, the output will be:

Area before scaling: 12
Area after scaling: 48

Method with Value vs Pointer Receiver

If a method uses a value receiver, it gets a copy of the receiver. Changes made inside the method do not affect the original value. A pointer receiver allows the method to modify the original value.

Example

Demonstrates how changes reflect only with pointer receivers:

package main
import "fmt"

type Counter struct {
    value int
}

// Method with value receiver (won’t modify original)
func (c Counter) incrementValue() {
    c.value++
}

// Method with pointer receiver (will modify original)
func (c *Counter) incrementPointer() {
    c.value++
}

func main() {
    c := Counter{value: 10}
    c.incrementValue()
    fmt.Println("After incrementValue:", c.value)

    c.incrementPointer()
    fmt.Println("After incrementPointer:", c.value)
}

When you run the above code, the output will be:

After incrementValue: 10
After incrementPointer: 11

Exercise

Test your understanding of methods in Go.

1. What is a method in Go? --Select-- A function with a receiver A type alias An interface
2. What does a pointer receiver allow a method to do? --Select-- Modify the original value Create a copy of the struct None of the above
3. Can both value and pointer receivers be used to define methods? --Select-- Yes No Only for interfaces