Vapor 3, Fluent 3 and Many-to-Many relations not working as expected

Question

Just started with Vapor 3 along with a MySQL database and I am having hard time figuring out the Relations part.

I have created 2 models so far: Movie and Actor. A Movie can have many Actors and an Actor can have many Movies.

Movie Model:

import Vapor
import FluentMySQL

final class Movie: Codable {

    var id: Int?
    var name: String
    var synopsis: String
    var dateReleased: Date
    var totalGrossed: Float

    init(id: Int? = nil, name: String, synopsis: String, dateReleased: Date, totalGrossed: Float) {
        self.id = id
        self.name = name
        self.synopsis = synopsis
        self.dateReleased = dateReleased
        self.totalGrossed = totalGrossed
    }

}

extension Movie {
    var actors: Siblings<Movie, Actor, MovieActor> {
        return siblings()
    }
}

extension Movie: Content {}
extension Movie: Parameter {}
extension Movie: MySQLModel {}

extension Movie: MySQLMigration {
    static func prepare(on conn: MySQLConnection) -> Future<Void> {
        return MySQLDatabase.create(self, on: conn) { builder in
            builder.field(for: \.id, isIdentifier: true)
            builder.field(for: \.name)
            builder.field(for: \.synopsis)
            builder.field(for: \.dateReleased, type: .date)
            builder.field(for: \.totalGrossed, type: .float)
        }
    }
}

Actor Model:

import Vapor
import FluentMySQL

final class Actor: Codable {

    var id: Int?
    var firstName: String
    var lastName: String
    var fullName: String {
        return firstName + " " + lastName
    }
    var dateOfBirth: Date
    var story: String

    init(id: Int? = nil, firstName: String, lastName: String, dateOfBirth: Date, story: String) {
        self.id = id
        self.firstName = firstName
        self.lastName = lastName
        self.dateOfBirth = dateOfBirth
        self.story = story
    }

}

extension Actor {
    var actors: Siblings<Actor, Movie, MovieActor> {
        return siblings()
    }
}

extension Actor: Content {}
extension Actor: Parameter {}
extension Actor: MySQLModel {}

extension Actor: MySQLMigration {
    static func prepare(on conn: MySQLConnection) -> Future<Void> {
        return MySQLDatabase.create(self, on: conn) { builder in
            builder.field(for: \.id, isIdentifier: true)
            builder.field(for: \.firstName)
            builder.field(for: \.lastName)
            builder.field(for: \.dateOfBirth, type: .date)
            builder.field(for: \.story, type: .text)
        }
    }
}

And I have also created a MovieActor model as a MySQLPivot for the relationship:

import Vapor
import FluentMySQL

final class MovieActor: MySQLPivot {

    typealias Left = Movie
    typealias Right = Actor

    static var leftIDKey: LeftIDKey = \.movieID
    static var rightIDKey: RightIDKey = \.actorID

    var id: Int?

    var movieID: Int
    var actorID: Int

    init(movieID: Int, actorID: Int) {
        self.movieID = movieID
        self.actorID = actorID
    }

}

extension MovieActor: MySQLMigration {}

And have added them to the migration section in the configure.swift file:

var migrations = MigrationConfig()
migrations.add(model: Movie.self, database: .mysql)
migrations.add(model: Actor.self, database: .mysql)
migrations.add(model: MovieActor.self, database: .mysql)
services.register(migrations)

All the tables in the database are being created just fine, but I am not receiving the relationship when calling the get all movies service. I am just receiving the Movie's properties:

final class MoviesController {

    func all(request: Request) throws -> Future<[Movie]> {

        return Movie.query(on: request).all()
    }

}

[
    {
        "id": 1,
        "dateReleased": "2017-11-20T00:00:00Z",
        "totalGrossed": 0,
        "name": "Star Wars: The Last Jedi",
        "synopsis": "Someone with a lightsaber kills another person with a lightsaber"
    },
    {
        "id": 3,
        "dateReleased": "1970-07-20T00:00:00Z",
        "totalGrossed": 0,
        "name": "Star Wars: A New Hope",
        "synopsis": "Someone new has been discovered by the force and he will kill the dark side with his awesome lightsaber and talking skills."
    },
    {
        "id": 4,
        "dateReleased": "2005-12-20T00:00:00Z",
        "totalGrossed": 100000000,
        "name": "Star Wars: Revenge of the Sith",
        "synopsis": "Anakin Skywalker being sliced by Obi-Wan Kenobi in an epic dual of fates"
    }
]

Your help would be appreciated! Thank you very much :)

Vince Vince · Accepted Answer · 2018-08-06T04:59:40

So I believe you're expecting the relationship to be reflected in what is returned when you query for a Movie model. So for example you expect something like this to be returned for a Movie:

{
    "id": 1,
    "dateReleased": "2017-11-20T00:00:00Z",
    "totalGrossed": 0,
    "name": "Star Wars: The Last Jedi",
    "synopsis": "Someone with a lightsaber kills another person with a lightsaber",
    "actors": [
        "id": 1,
        "firstName": "Leonardo",
        "lastName": "DiCaprio",
        "dateOfBirth": "1974-11-11T00:00:00Z",
        "story": "Couldn't get an Oscar until wrestling a bear for the big screen."
    ]
}

However, connecting the Movie and Actor models as siblings simply just gives you the convenience of being able to query the actors from a movie as if the actors were a property of the Movie model:

movie.actors.query(on: request).all()

That line above returns: Future<[Actor]>

This works vice versa for accessing the movies from an Actor object:

actor.movies.query(on: request).all()

That line above returns: Future<[Movie]>

If you wanted it to return both the movie and its actors in the same response like how I assumed you wanted it to work above, I believe the best way to do this would be creating a Content response struct like this:

struct MovieResponse: Content {

    let movie: Movie
    let actors: [Actor]
}

Your "all" function would now look like this:

func all(_ request: Request) throws -> Future<[MovieResponse]> {

    return Movie.query(on: request).all().flatMap { movies in

        let movieResponseFutures = try movies.map { movie in
            try movie.actors.query(on: request).all().map { actors in
                return MovieResponse(movie: movie, actors: actors)
            }
        }

        return movieResponseFutures.flatten(on: request)
    }
}

This function queries all of the movies and then iterates through each movie and then uses the "actors" sibling relation to query for that movie's actors. This actors query returns a Future<[Actor]> for each movie it queries the actors for. Map what is returned from the that relation so that you can access the actors as [Actor] instead of Future<[Actor]>, and then return that combined with the movie as a MovieResponse.

What this movieResponseFutures actually consists of is an array of MovieResponse futures: [Future<[MovieResponse]>]

To turn that array of futures into a single future that consists of an array you use flatten(on:). This waits waits for each of those individual futures to finish and then returns them all as a single future.

If you really wanted the Actor's array inside of the Movie object json, then you could structure the MovieResponse struct like this:

struct MovieResponse: Content {

    let id: Int?
    let name: String
    let synopsis: String
    let dateReleased: Date
    let totalGrossed: Float
    let actors: [Actor]

    init(movie: Movie, actors: [Actor]) {
        self.id = movie.id
        self.name = movie.name
        self.synopsis = movie.synopsis
        self.dateReleased = movie.dateReleased
        self.totalGrossed = movie.totalGrossed
        self.actors = actors
    }
}

Vapor 3, Fluent 3 and Many-to-Many relations not working as expected

2 Answers