Interface Implementation in Go

Interfaces are implemented implicitly in Go. Think of interfaces in Go like a rule book that says: “If you can do these things, then you belong to this group.”

Let's visualize this with a simple example.

Step 1: Define an interface (The Rule book)

package main

import "fmt"

// ToyCar is the rule book (interface) that says a car must have Drive() and Honk()
type ToyCar interface {
    Drive()
    Honk()
}

Step 2: Create a Struct

Now, we create a struct (RemoteCar) that follows these rules.

// RemoteCar is a real toy car that can drive and honk
type RemoteCar struct{}

// RemoteCar has a Drive() method (so it follows part of the rule book)
func (r RemoteCar) Drive() {
    fmt.Println("Vroom! The car is driving!")
}

// RemoteCar has a Honk() method (so it fully follows the rule book)
func (r RemoteCar) Honk() {
    fmt.Println("Beep beep! The car is honking!")
}

Since RemoteCar has both Drive() and Honk(), it automatically belongs to the ToyCar group—without us saying anything!

Step 3: Let's create a Function to Check if It Follows the Rule book

If we write a function that accepts only things that follow ToyCar, and it works with RemoteCar, that means RemoteCar follows the rules!

// PlayWithToy takes anything that follows the ToyCar rules
func PlayWithToy(car ToyCar) {
    car.Drive()
    car.Honk()
}

Step 4: Let's Test It

Now, let's test it inside main():

func main() {
    myCar := RemoteCar{} // Create a toy car
    PlayWithToy(myCar)   // Check if it follows the rules
}

Expected Output:

Vroom! The car is driving!
Beep beep! The car is honking!

What Just Happened?

• We never explicitly said RemoteCar implements ToyCar, but since it has all the required methods, Go automatically considers it part of ToyCar.
• If we removed Honk() from RemoteCar, the program wouldn't compile, because RemoteCar wouldn't fully match the ToyCar rule book.

This is what we mean when we say “Interfaces are implemented implicitly in Go”—you don't have to declare it; if a type matches, it is that interface.