Movies MVC Application

Iris has a very powerful and blazing fast MVC support, you can return any value of any type from a method function and it will be sent to the client as expected.

  • if string then it's the body.
  • if string is the second output argument then it's the content type.
  • if int then it's the status code.
  • if error and not nil then (any type) response will be omitted and error's text with a 400 bad request will be rendered instead.
  • if (int, error) and error is not nil then the response result will be the error's text with the status code as int.
  • if custom struct or interface{} or slice or map then it will be rendered as json, unless a string content type is following.
  • if mvc.Result then it executes its Dispatch function, so good design patters can be used to split the model's logic where needed.

Nothing stops you from using your favorite folder structure. Iris is a low level web framework, it has got MVC first-class support but it doesn't limit your folder structure, this is your choice.

Structuring depends on your own needs. We can't tell you how to design your own application for sure but you're free to take a closer look to one of use-case examples below;

folder structure example.

Data Model Layer

Let's start with our model, the Movie.

// file: datamodels/movie.go

package datamodels

// Movie is our sample data structure.
// Keep note that the tags for public-use (for our web app)
// should be kept in other file like "web/viewmodels/movie.go"
// which could wrap by embedding the datamodels.Movie or
// declare new fields instead butwe will use this datamodel
// as the only one Movie model in our application,
// for the shake of simplicty.
type Movie struct {
    ID     int64  `json:"id"`
    Name   string `json:"name"`
    Year   int    `json:"year"`
    Genre  string `json:"genre"`
    Poster string `json:"poster"`
}

Data Source / Data Store Layer

After that, we continue by creating a simple memory storage for our Movies.

// file: datasource/movies.go

package datasource

import "github.com/kataras/iris/_examples/mvc/overview/datamodels"

// Movies is our imaginary data source.
var Movies = map[int64]datamodels.Movie{
    1: {
        ID:     1,
        Name:   "Casablanca",
        Year:   1942,
        Genre:  "Romance",
        Poster: "https://iris-go.com/images/examples/mvc-movies/1.jpg",
    },
    2: {
        ID:     2,
        Name:   "Gone with the Wind",
        Year:   1939,
        Genre:  "Romance",
        Poster: "https://iris-go.com/images/examples/mvc-movies/2.jpg",
    },
    3: {
        ID:     3,
        Name:   "Citizen Kane",
        Year:   1941,
        Genre:  "Mystery",
        Poster: "https://iris-go.com/images/examples/mvc-movies/3.jpg",
    },
    4: {
        ID:     4,
        Name:   "The Wizard of Oz",
        Year:   1939,
        Genre:  "Fantasy",
        Poster: "https://iris-go.com/images/examples/mvc-movies/4.jpg",
    },
    5: {
        ID:     5,
        Name:   "North by Northwest",
        Year:   1959,
        Genre:  "Thriller",
        Poster: "https://iris-go.com/images/examples/mvc-movies/5.jpg",
    },
}

Repositories

The layer which has direct access to the "datasource" and can manipulate data directly.

Optionally (because you could have that inside a Service as well), but required for that example, we create a Repository, a repository handles the "low-level", the direct access to the Movies datasource. Keep that "a Repository", it's an interface because it can differs, it depends on the state of your app development, i.e in production will use some real sql queries or anything else you use for quering data.

// file: repositories/movie_repository.go

package repositories

import (
    "errors"
    "sync"

    "github.com/kataras/iris/_examples/mvc/overview/datamodels"
)

// Query represents the visitor and action queries.
type Query func(datamodels.Movie) bool

// MovieRepository handles the basic operations of a movie entity/model.
// It's an interface in order to be testable, i.e a memory movie repository or
// a connected to an sql database.
type MovieRepository interface {
    Exec(query Query, action Query, limit int, mode int) (ok bool)

    Select(query Query) (movie datamodels.Movie, found bool)
    SelectMany(query Query, limit int) (results []datamodels.Movie)

    InsertOrUpdate(movie datamodels.Movie) (updatedMovie datamodels.Movie, err error)
    Delete(query Query, limit int) (deleted bool)
}

// NewMovieRepository returns a new movie memory-based repository,
// the one and only repository type in our example.
func NewMovieRepository(source map[int64]datamodels.Movie) MovieRepository {
    return &movieMemoryRepository{source: source}
}

// movieMemoryRepository is a "MovieRepository"
// which manages the movies using the memory data source (map).
type movieMemoryRepository struct {
    source map[int64]datamodels.Movie
    mu     sync.RWMutex
}

const (
    // ReadOnlyMode will RLock(read) the data .
    ReadOnlyMode = iota
    // ReadWriteMode will Lock(read/write) the data.
    ReadWriteMode
)

func (r *movieMemoryRepository) Exec(query Query, action Query, actionLimit int, mode int) (ok bool) {
    loops := 0

    if mode == ReadOnlyMode {
        r.mu.RLock()
        defer r.mu.RUnlock()
    } else {
        r.mu.Lock()
        defer r.mu.Unlock()
    }

    for _, movie := range r.source {
        ok = query(movie)
        if ok {
            if action(movie) {
                loops++
                if actionLimit >= loops {
                    break // break
                }
            }
        }
    }

    return
}

// Select receives a query function
// which is fired for every single movie model inside
// our imaginary data source.
// When that function returns true then it stops the iteration.
//
// It returns the query's return last known "found" value
// and the last known movie model
// to help callers to reduce the LOC.
//
// It's actually a simple but very clever prototype function
// I'm using everywhere since I firstly think of it,
// hope you'll find it very useful as well.
func (r *movieMemoryRepository) Select(query Query) (movie datamodels.Movie, found bool) {
    found = r.Exec(query, func(m datamodels.Movie) bool {
        movie = m
        return true
    }, 1, ReadOnlyMode)

    // set an empty datamodels.Movie if not found at all.
    if !found {
        movie = datamodels.Movie{}
    }

    return
}

// SelectMany same as Select but returns one or more datamodels.Movie as a slice.
// If limit <=0 then it returns everything.
func (r *movieMemoryRepository) SelectMany(query Query, limit int) (results []datamodels.Movie) {
    r.Exec(query, func(m datamodels.Movie) bool {
        results = append(results, m)
        return true
    }, limit, ReadOnlyMode)

    return
}

// InsertOrUpdate adds or updates a movie to the (memory) storage.
//
// Returns the new movie and an error if any.
func (r *movieMemoryRepository) InsertOrUpdate(movie datamodels.Movie) (datamodels.Movie, error) {
    id := movie.ID

    if id == 0 { // Create new action
        var lastID int64
        // find the biggest ID in order to not have duplications
        // in productions apps you can use a third-party
        // library to generate a UUID as string.
        r.mu.RLock()
        for _, item := range r.source {
            if item.ID > lastID {
                lastID = item.ID
            }
        }
        r.mu.RUnlock()

        id = lastID + 1
        movie.ID = id

        // map-specific thing
        r.mu.Lock()
        r.source[id] = movie
        r.mu.Unlock()

        return movie, nil
    }

    // Update action based on the movie.ID,
    // here we will allow updating the poster and genre if not empty.
    // Alternatively we could do pure replace instead:
    // r.source[id] = movie
    // and comment the code below;
    current, exists := r.Select(func(m datamodels.Movie) bool {
        return m.ID == id
    })

    if !exists { // ID is not a real one, return an error.
        return datamodels.Movie{}, errors.New("failed to update a nonexistent movie")
    }

    // or comment these and r.source[id] = m for pure replace
    if movie.Poster != "" {
        current.Poster = movie.Poster
    }

    if movie.Genre != "" {
        current.Genre = movie.Genre
    }

    // map-specific thing
    r.mu.Lock()
    r.source[id] = current
    r.mu.Unlock()

    return movie, nil
}

func (r *movieMemoryRepository) Delete(query Query, limit int) bool {
    return r.Exec(query, func(m datamodels.Movie) bool {
        delete(r.source, m.ID)
        return true
    }, limit, ReadWriteMode)
}

Services

The layer which has access to call functions from the "repositories" and "models" (or even "datamodels" if simple application). It should contain the most of the domain logic.

We need a service to communicate with our repository in the "high-level" and store/retrieve Movies, this will be used on the Web Controllers below.

// file: services/movie_service.go

package services

import (
    "github.com/kataras/iris/_examples/mvc/overview/datamodels"
    "github.com/kataras/iris/_examples/mvc/overview/repositories"
)

// MovieService handles some of the CRUID operations of the movie datamodel.
// It depends on a movie repository for its actions.
// It's here to decouple the data source from the higher level compoments.
// As a result a different repository type can be used with the same logic without any aditional changes.
// It's an interface and it's used as interface everywhere
// because we may need to change or try an experimental different domain logic at the future.
type MovieService interface {
    GetAll() []datamodels.Movie
    GetByID(id int64) (datamodels.Movie, bool)
    DeleteByID(id int64) bool
    UpdatePosterAndGenreByID(id int64, poster string, genre string) (datamodels.Movie, error)
}

// NewMovieService returns the default movie service.
func NewMovieService(repo repositories.MovieRepository) MovieService {
    return &movieService{
        repo: repo,
    }
}

type movieService struct {
    repo repositories.MovieRepository
}

// GetAll returns all movies.
func (s *movieService) GetAll() []datamodels.Movie {
    return s.repo.SelectMany(func(_ datamodels.Movie) bool {
        return true
    }, -1)
}

// GetByID returns a movie based on its id.
func (s *movieService) GetByID(id int64) (datamodels.Movie, bool) {
    return s.repo.Select(func(m datamodels.Movie) bool {
        return m.ID == id
    })
}

// UpdatePosterAndGenreByID updates a movie's poster and genre.
func (s *movieService) UpdatePosterAndGenreByID(id int64, poster string, genre string) (datamodels.Movie, error) {
    // update the movie and return it.
    return s.repo.InsertOrUpdate(datamodels.Movie{
        ID:     id,
        Poster: poster,
        Genre:  genre,
    })
}

// DeleteByID deletes a movie by its id.
//
// Returns true if deleted otherwise false.
func (s *movieService) DeleteByID(id int64) bool {
    return s.repo.Delete(func(m datamodels.Movie) bool {
        return m.ID == id
    }, 1)
}

View Models

There should be the view models, the structure that the client will be able to see.

Example:

import (
    "github.com/kataras/iris/_examples/mvc/overview/datamodels"

    "github.com/kataras/iris/context"
)

type Movie struct {
    datamodels.Movie
}

func (m Movie) IsValid() bool {
    /* do some checks and return true if it's valid... */
    return m.ID > 0
}

Iris is able to convert any custom data Structure into an HTTP Response Dispatcher, so theoritically, something like the following is permitted if it's really necessary;

// Dispatch completes the `kataras/iris/mvc#Result` interface.
// Sends a `Movie` as a controlled http response.
// If its ID is zero or less then it returns a 404 not found error
// else it returns its json representation,
// (just like the controller's functions do for custom types by default).
//
// Don't overdo it, the application's logic should not be here.
// It's just one more step of validation before the response,
// simple checks can be added here.
//
// It's just a showcase,
// imagine the potentials this feature gives when designing a bigger application.
//
// This is called where the return value from a controller's method functions
// is type of `Movie`.
// For example the `controllers/movie_controller.go#GetBy`.
func (m Movie) Dispatch(ctx context.Context) {
    if !m.IsValid() {
        ctx.NotFound()
        return
    }
    ctx.JSON(m, context.JSON{Indent: " "})
}

However, we will use the "datamodels" as the only one models package because Movie structure doesn't contain any sensitive data, clients are able to see all of its fields and we don't need any extra functionality or validation inside it.

Controllers

Handles web requests, bridge between the services and the client.

And the most important, here's where Iris comes, is the Controller which will communicate with a MovieService. We usually store all http-relative things in a different folder called "web" so all controllers can be inside "web/controllers", note that "usually" you can use other design patterns as well, it's up to you.

// file: web/controllers/movie_controller.go

package controllers

import (
    "errors"

    "github.com/kataras/iris/_examples/mvc/overview/datamodels"
    "github.com/kataras/iris/_examples/mvc/overview/services"

    "github.com/kataras/iris"
)

// MovieController is our /movies controller.
type MovieController struct {
    // Our MovieService, it's an interface which
    // is binded from the main application.
    Service services.MovieService
}

// Get returns list of the movies.
// Demo:
// curl -i http://localhost:8080/movies
//
// The correct way if you have sensitive data:
// func (c *MovieController) Get() (results []viewmodels.Movie) {
//     data := c.Service.GetAll()
//
//     for _, movie := range data {
//         results = append(results, viewmodels.Movie{movie})
//     }
//     return
// }
// otherwise just return the datamodels.
func (c *MovieController) Get() (results []datamodels.Movie) {
    return c.Service.GetAll()
}

// GetBy returns a movie.
// Demo:
// curl -i http://localhost:8080/movies/1
func (c *MovieController) GetBy(id int64) (movie datamodels.Movie, found bool) {
    return c.Service.GetByID(id) // it will throw 404 if not found.
}

// PutBy updates a movie.
// Demo:
// curl -i -X PUT -F "genre=Thriller" -F "poster=@/Users/kataras/Downloads/out.gif" http://localhost:8080/movies/1
func (c *MovieController) PutBy(ctx iris.Context, id int64) (datamodels.Movie, error) {
    // get the request data for poster and genre
    file, info, err := ctx.FormFile("poster")
    if err != nil {
        return datamodels.Movie{}, errors.New("failed due form file 'poster' missing")
    }
    // we don't need the file so close it now.
    file.Close()

    // imagine that is the url of the uploaded file...
    poster := info.Filename
    genre := ctx.FormValue("genre")

    return c.Service.UpdatePosterAndGenreByID(id, poster, genre)
}

// DeleteBy deletes a movie.
// Demo:
// curl -i -X DELETE -u admin:password http://localhost:8080/movies/1
func (c *MovieController) DeleteBy(id int64) interface{} {
    wasDel := c.Service.DeleteByID(id)
    if wasDel {
        // return the deleted movie's ID
        return iris.Map{"deleted": id}
    }
    // right here we can see that a method function can return any of those two types(map or int),
    // we don't have to specify the return type to a specific type.
    return iris.StatusBadRequest
}

A middleware inside "web/middleware", for the shake of the example.

// file: web/middleware/basicauth.go

package middleware

import "github.com/kataras/iris/middleware/basicauth"

// BasicAuth middleware sample.
var BasicAuth = basicauth.New(basicauth.Config{
    Users: map[string]string{
        "admin": "password",
    },
})

And finally our main.go.

// file: main.go

package main

import (
    "github.com/kataras/iris/_examples/mvc/overview/datasource"
    "github.com/kataras/iris/_examples/mvc/overview/repositories"
    "github.com/kataras/iris/_examples/mvc/overview/services"
    "github.com/kataras/iris/_examples/mvc/overview/web/controllers"
    "github.com/kataras/iris/_examples/mvc/overview/web/middleware"

    "github.com/kataras/iris"
    "github.com/kataras/iris/mvc"
)

func main() {
    app := iris.New()
    app.Logger().SetLevel("debug")

    // Load the template files.
    app.RegisterView(iris.HTML("./web/views", ".html"))

    // Register our controllers.
    // mvc.New(app.Party("/movies")).Handle(new(controllers.MovieController))
    // But,
    // You can also split the code you write to configure an mvc.Application
    // using the `mvc.Configure` method, as shown below.
    mvc.Configure(app.Party("/movies"), movies)

    // http://localhost:8080/movies
    // http://localhost:8080/movies/1
    app.Run(
        // Start the web server at localhost:8080
        iris.Addr("localhost:8080"),
        // disables updates:
        iris.WithoutVersionChecker,
        // skip err server closed when CTRL/CMD+C pressed:
        iris.WithoutServerError(iris.ErrServerClosed),
        // enables faster json serialization and more:
        iris.WithOptimizations,
    )
}

// note the mvc.Application, it's not iris.Application.
func movies(app *mvc.Application) {
    // Add the basic authentication(admin:password) middleware
    // for the /movies based requests.
    app.Router.Use(middleware.BasicAuth)

    // Create our movie repository with some (memory) data from the datasource.
    repo := repositories.NewMovieRepository(datasource.Movies)
    // Create our movie service, we will bind it to the movie app's dependencies.
    movieService := services.NewMovieService(repo)
    app.Register(movieService)

    // serve our movies controller.
    // Note that you can serve more than one controller
    // you can also create child mvc apps using the `movies.Party(relativePath)` or `movies.Clone(app.Party(...))`
    // if you want.
    app.Handle(new(controllers.MovieController))
}

Click here to navigate to the MVC loves Websockets.


results matching ""

    No results matching ""