Benefits of interfaces in GO

In GO, the interfaces are different from other popular programming languages ​​such as Java, C ++, PHP. They have some design advantages. In this article I will try to explain why.

I'll cover the benefits, provide examples, and discuss some of the issues that may arise when using interfaces.

What is special about interfaces in GO?

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class Human implements Walkable
{
…
}

class Mountain
{
    public function walkAround(Walkable $walkable) {...}
}

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$human = new Human();
$mountain = new Mountain();
$mountain.walkAround($human);

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package auth

import (
   "gitlab.com/excercice_detection/backend"
)

type userRepository interface {
   FindUserByEmail(email string) (backend.User, error)
   AddUser(backend.User) (userID int, err error)
   AddToken(userID int, token string) error
   TokenExists(userID int, token string) bool
}

// Auth  
type Auth struct {
   repository userRepository
   logger     backend.Logger
}

// NewAuth   
func NewAuth(repository userRepository, logger backend.Logger) *Auth {
   return &Auth{repository, logger}
}

// Autentificate    
func (auth Auth) Autentificate(userID int, token string) bool {
   return auth.repository.TokenExists(userID, token)
}

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main :

package main

import (
   "gitlab.com/excercice_detection/backend/auth"
   "gitlab.com/excercice_detection/backend/mysql"
)

func main() {
    logger := newLogger()
    userRepository := mysql.NewUserRepository(logger)
    err := userRepository.Connect()
    authService := auth.NewAuth(userRepository, logger)
...

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type userRepositoryMock struct {
   user         backend.User
   findUserErr  error
   addUserError error
   addUserID    int
   addTokenErr  error
   tokenExists  bool
}

func (repository userRepositoryMock) FindUserByEmail(email string) (backend.User, error) {
   return repository.user, repository.findUserErr
}

func (repository userRepositoryMock) AddUser(backend.User) (userID int, err error) {
   return repository.addUserID, repository.addUserError
}

func (repository userRepositoryMock) AddToken(userID int, token string) error {
   return repository.addTokenErr
}

func (repository userRepositoryMock) TokenExists(userID int, token string) bool {
   return repository.tokenExists
}

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