Pointer Receivers

Part of the Logic & Flow section of Coddy's GO journey — lesson 8 of 68.

While value receivers work with copies of structs, pointer receivers work directly with the original struct instance. When you define a method with a pointer receiver, the method can modify the original data because it receives a pointer to the struct rather than a copy.

To create a pointer receiver, you add an asterisk * before the type name in the receiver declaration:

type Person struct {
    Name string
    Age  int
}

func (p *Person) haveBirthday() {
    p.Age++  // This modifies the original struct
}

In this example, (p *Person) is a pointer receiver. When you call the haveBirthday method on a Person instance, the method receives a pointer to the original struct. Any changes made to the struct fields through this pointer will permanently modify the original data.

Pointer receivers are essential when your methods need to update the struct's fields, making them perfect for operations that change the state of your data.

Test yourself

This lesson includes a short quiz. Start the lesson to answer it and track your progress.

Test yourself

This lesson includes a short quiz. Start the lesson to answer it and track your progress.

Test yourself

This lesson includes a short quiz. Start the lesson to answer it and track your progress.

Challenge

Easy

In this challenge, you'll practice creating methods with pointer receivers by building a simple bank account system. You'll create an Account struct and define methods that can modify the account balance using pointer receivers.

You will receive three inputs:

A string representing the account holder's name (e.g., "John Smith")
A string representing the initial account balance (e.g., "1000.50")
A string representing a transaction amount (e.g., "250.75")

Your task is to:

Define an Account struct with two fields: Name (string) and Balance (float64)
Create a method called deposit with a pointer receiver that adds the given amount to the account balance
Create a method called withdraw with a pointer receiver that subtracts the given amount from the account balance
Create a method called displayBalance with a value receiver that prints the account information in the format: "Account: [name], Balance: $[balance]"
Parse the inputs to create an Account instance
Call displayBalance to show the initial balance
Call deposit with the transaction amount
Call displayBalance to show the balance after deposit
Call withdraw with the transaction amount
Call displayBalance to show the final balance

The balance should be displayed with two decimal places precision. This challenge demonstrates how pointer receivers allow methods to modify the original struct data, unlike value receivers which work with copies.

Cheat sheet

Pointer receivers work directly with the original struct instance by receiving a pointer to the struct rather than a copy. This allows methods to modify the original data.

To create a pointer receiver, add an asterisk * before the type name in the receiver declaration:

type Person struct {
    Name string
    Age  int
}

func (p *Person) haveBirthday() {
    p.Age++  // This modifies the original struct
}

Use pointer receivers when your methods need to update the struct's fields, making them perfect for operations that change the state of your data.

Try it yourself

package main

import (
	"fmt"
	"strconv"
)

// TODO: Define the Account struct here

// TODO: Define the deposit method with pointer receiver here

// TODO: Define the withdraw method with pointer receiver here

// TODO: Define the displayBalance method with value receiver here

func main() {
	// Read input
	var name string
	var initialBalanceStr string
	var transactionAmountStr string
	
	fmt.Scanln(&name)
	fmt.Scanln(&initialBalanceStr)
	fmt.Scanln(&transactionAmountStr)
	
	// Convert string inputs to appropriate types
	initialBalance, _ := strconv.ParseFloat(initialBalanceStr, 64)
	transactionAmount, _ := strconv.ParseFloat(transactionAmountStr, 64)
	
	// TODO: Create an Account instance
	
	// TODO: Display initial balance, perform deposit, display balance, perform withdrawal, display final balance
}

Test yourself

This lesson includes a short quiz. Start the lesson to answer it and track your progress.