Structs & Custom Methods

🐹 Go Language Lesson 10 Intermediate

Go does not have classes or objects. Instead, custom data structures are defined using structs, and methods are bound to structs using receiver functions.

1 Value vs. Pointer Receivers

Methods are functions declared with a **Receiver** argument, which binds the function to a specific type. There are two types of receivers:

Value Receiver: Passes a copy of the struct. Modifying struct fields inside the method does not affect the original object.
Pointer Receiver (`*Type`): Passes a pointer to the struct. Modifying fields inside the method changes the original object directly. Used to avoid copying large structures in memory.

2 Structs & Methods Code

Let's run a program declaring structures and binding value/pointer receiver methods:

Go — Structs & Receivers ▶ Run Code

package main

import "fmt"

struct Student {
    Name  string
    Grade float64
}

// Value Receiver (cannot modify original struct)
func (s Student) printDetails() {
    fmt.Printf("Student: %s, Grade: %.2f\n", s.Name, s.Grade)
}

// Pointer Receiver (modifies original struct)
func (s *Student) updateGrade(newGrade float64) {
    s.Grade = newGrade
}

func main() {
    s := Student{Name: "Alice", Grade: 3.8}
    s.printDetails()

    s.updateGrade(3.95) // Automatically passes pointer reference
    s.printDetails()     // Displays updated grade
}

3 Code Challenge

Challenge: Write a struct called `Car` with a property `Speed` (int). Create a pointer receiver method called `Accelerate(amount int)` that increases the speed. Instantiate a car, accelerate it by `30`, and print the updated speed.