Defining methods in Go - Mini Project: Build & Apply

Defining methods in Go

📖 Scenario: You are creating a simple program to represent a Car with its brand and speed. You want to add a method to the Car that can display its current speed in a friendly message.

🎯 Goal: Build a Go program that defines a Car struct and adds a method DisplaySpeed to it. The method should print the car's brand and speed in a sentence.

📋 What You'll Learn

Create a struct called Car with fields Brand (string) and Speed (int).

Create a variable myCar of type Car with brand "Toyota" and speed 120.

Define a method DisplaySpeed with a receiver of type Car that prints the brand and speed.

Call the DisplaySpeed method on myCar to show the output.

💡 Why This Matters

🌍 Real World

Defining methods on structs is how Go programs model real-world objects with both data and actions, like cars, users, or bank accounts.

💼 Career

Understanding methods and structs is essential for Go developers building backend services, tools, or any software that needs organized data and behavior.

1

Create the Car struct and a variable

Create a struct called Car with fields Brand of type string and Speed of type int. Then create a variable called myCar of type Car with Brand set to "Toyota" and Speed set to 120.

Go

// Define the Car struct and create myCar variable
// Your code here

Hint

Use type Car struct { ... } to define the struct. Create myCar with Car{Brand: "Toyota", Speed: 120}.

2

Add a method DisplaySpeed to Car

Define a method called DisplaySpeed with a receiver of type Car. The method should print the message: "The is moving at km/h." using fmt.Printf. Use receiver name c.

Go

package main

import "fmt"

type Car struct {
    Brand string
    Speed int
}

// Define DisplaySpeed method for Car here
// Your code here

func main() {
    myCar := Car{Brand: "Toyota", Speed: 120}
}

Hint

Use func (c Car) DisplaySpeed() to define the method. Use fmt.Printf to print the message with c.Brand and c.Speed.

3

Call the DisplaySpeed method on myCar

Inside the main function, call the DisplaySpeed method on the variable myCar.

Go

package main

import "fmt"

type Car struct {
    Brand string
    Speed int
}

func (c Car) DisplaySpeed() {
    fmt.Printf("The %s is moving at %d km/h.\n", c.Brand, c.Speed)
}

func main() {
    myCar := Car{Brand: "Toyota", Speed: 120}
    // Call DisplaySpeed method on myCar
    // Your code here
}

Hint

Call the method with myCar.DisplaySpeed() inside main.

4

Print the output

Run the program so it prints the message from the DisplaySpeed method.

Go

package main

import "fmt"

type Car struct {
    Brand string
    Speed int
}

func (c Car) DisplaySpeed() {
    fmt.Printf("The %s is moving at %d km/h.\n", c.Brand, c.Speed)
}

func main() {
    myCar := Car{Brand: "Toyota", Speed: 120}
    myCar.DisplaySpeed()
    // Program output should appear above
}

Hint

Run the program to see the message printed exactly as: The Toyota is moving at 120 km/h.