Interfaces in Golang

If you’re coming from Java, you definitely know about interfaces. If you’re coming from Python, you’re probably scratching your head. But, no matter which language you’re coming from, you’ll be surprised about how Go implements interfaces.

An interface is a type in Go. But, unlike the struct type, the interface type is not concerned with state, but with behavior.

For example, a Dog struct would look like this:

type Dog struct {
    name     string
    age       int
    gender  string
    isHungry bool
}

A Dog interface on the other hand would look like this:

type Dog interface {
    barks()
    eats()
}

The struct shows us some attributes of a dog, but the interface describes what this dog is supposed to do.

Now, let’s say we’re writing an application about .. well… dogs! We’ll have a lot of different breeds. We know that Go does not support inheritance like OOP languages do , so instead of naming the struct Dog, let’s name it Labrador, and as our app grows, we’ll probably add more breeds.

type Labrador struct {
    name     string
    age    int
    gender string
    isHungry bool
}

For the purpose of our app, we’ll want to split these different dogs into two groups — big dogs and small dogs ( suppose we…