[Author: @mdimamhosen Date: 2025-04-22 Category: interview-qa/Receiver Function Tags: [go, Receiver Function] ]

📦 Receiver Function in Go

A receiver function in Go is a method bound to a specific type—typically a struct. It enables you to implement object-oriented behavior by defining methods on user-defined types.

🧱 Struct and Receiver Basics

Struct Definition

// User struct with basic fields
type User struct {
	Name string
	Age  int
}

📞 Regular Function vs Receiver Function

Regular Function

func printUser(user User) {
	fmt.Println("User Name:", user.Name)
	fmt.Println("User Age:", user.Age)
}

This is a standalone function that takes User as a parameter.

Value Receiver Method

func (u User) printDetails() {
	fmt.Println("Name:", u.Name)
	fmt.Println("Age:", u.Age)
}

Here, printDetails() is associated with User type using a value receiver. It works on a copy, so original data won’t change.

Pointer Receiver Method

func (u *User) updateAge(newAge int) {
	u.Age = newAge
}

This method modifies the original User struct because it uses a pointer receiver.

✅ Main Function with Usage

func main() {
	user1 := User{Name: "John", Age: 30}
	user2 := User{Name: "Jane", Age: 25}

	// Regular function call
	printUser(user1)

	// Receiver function calls
	user1.printDetails()
	user2.printDetails()

	// Update age using pointer receiver
	user1.updateAge(35)
	fmt.Println("Updated Age of user1:", user1.Age)

	// Demonstrate value receiver (no change to original)
	user2.call(100)
	fmt.Println("User2's age after call():", user2.Age)
}

🔍 Additional Receiver Method

// Value receiver that does not affect original struct
func (u User) call(age int) {
	u.Age = age
	fmt.Println("Inside call() - temporary age:", u.Age)
}

This will not change the actual User.Age outside the function.

🧪 Example Output

User Name: John
User Age: 30
Name: John
Age: 30
Name: Jane
Age: 25
Updated Age of user1: 35
Inside call() - temporary age: 100
User2's age after call(): 25

💡 Key Takeaways

• ✅ Value receivers are good for read-only operations.
• ✅ Pointer receivers are used when you want to modify the actual data.
• ✅ Go supports object-like behavior through receiver functions.
• ✅ Methods with pointer receivers can be called on both values and pointers.

10 Interview Questions and Answers

1. What is a receiver function in Go?

   • A receiver function is a method associated with a specific type, allowing you to define methods on structs or other types.

2. What is the difference between a value receiver and a pointer receiver?

   • A value receiver operates on a copy of the object, while a pointer receiver operates on the actual object, allowing modifications.

3. Can you define multiple receiver functions for the same type?

   • Yes, you can define multiple receiver functions for the same type.

4. What is the syntax for defining a receiver function?

   • func (receiverType TypeName) methodName(parameters) {}

5. Can receiver functions be used with built-in types?

   • No, receiver functions can only be defined for user-defined types.

6. What happens if you call a value receiver function on a pointer?

   • Go automatically dereferences the pointer, so the function works as expected.

7. What is the purpose of receiver functions?

   • They enable object-oriented programming by associating methods with types.

8. Can a receiver function modify the original object?

   • Only if it uses a pointer receiver.

9. What is the difference between a regular function and a receiver function?

   • A regular function is not associated with any type, while a receiver function is tied to a specific type.

10. Can you use receiver functions with interfaces?

    • Yes, receiver functions are often used to implement interface methods.

Example Output

User Name: John
User Age: 30
User Name: Jane
User Age: 25
User Age: 10
User Age: 20