Golang Interfaces: Optional Functions

A simple set of code snippets that show you how to facilitate optional functions for interfaces and the structs that implement them

Folder Structure

examples -/
    garage -/
        car.go
        bmx.go
        ford.go
    main.go

Car interface with an optional honk function as an option for a car.

#garage/car.go
package garage

type Car interface {
   Drive()
}

type Options interface {
   honk()
}

func Honk(car Car) {
   # checks if this car has the honk option then executes
   if carWithOptions, ok := car.(Options); ok {
      carWithOptions.honk()
   } else {
      println("not implemented")
   }
}

We’ll implement a Ford car that drives and honks

#garage/ford.go
package garage

type Ford struct {
   Name string
}

func (Ford) Drive(){
   println("ford is driving")
}

func (Ford) honk() {
   println("HONK!!!")
}

Now we want to implement a bmx cycle that “drives” but does not have a horn to honk

# garage/bmx.go
package garage

type Bmx struct {
   Name string
}

func (Bmx) Drive(){
   println("bmx is cycling")
}

Imports garage lib and creates car objects to test.

#main.go
package main
import (
    "fmt"
    "examples/garage"
)
# Need to use the car interfaces function Honk to handle the optional honk() function
func main() {
    ford := garage.Ford{"Ford"}
    ford.Drive()
    garage.Honk(ford)
    bmx := garage.Bmx{"Bmx"}
    bmx.Drive()
    garage.Honk(bmx)
}

Output when run:

ford is driving
HONK!!!
bmx is cycling
not implemented

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