The repository sample for Vapor 4


Fluent is basically damaged


The extra I exploit the Fluent ORM framework the extra I notice how laborious it’s to work with it. I am speaking a few specific design challenge that I additionally talked about within the way forward for server aspect Swift article. I actually don’t love the concept of property wrappers and summary database fashions.


What’s the issue with the present database mannequin abstraction? Initially, the non-compulsory ID property is complicated. For instance you do not have to supply an identifier once you insert a report, it may be an nil worth and the ORM system can create a novel identifier (beneath the hood utilizing a generator) for you. So why do we now have an id for create operations in any respect? Sure, you may say that it’s potential to specify a customized identifier, however truthfully what number of occasions do we’d like that? If you wish to establish a report that is going to be one thing like a key, not an id discipline. 🙃


Additionally this non-compulsory property may cause another points, when utilizing fluent you’ll be able to require an id, which is a throwing operation, alternatively you’ll be able to unwrap the non-compulsory property should you’re positive that the identifier already exists, however this isn’t a secure strategy in any respect.


My different challenge is said to initializers, should you outline a customized mannequin you at all times have to supply an empty init() {} technique for it, in any other case the compiler will complain, as a result of fashions need to be lessons. BUT WHY? IMHO the rationale pertains to this challenge: you’ll be able to question the database fashions utilizing the mannequin itself. So the mannequin acts like a repository that you need to use to question the fields, and it additionally represents the the report itself. Is not this towards the clear rules? 🤔


Okay, one very last thing. Property wrappers, discipline keys and migrations. The core members at Vapor informed us that this strategy will present a secure approach to question my fashions and I can make sure that discipline keys will not be tousled, however I am truly scuffling with versioning on this case. I needed to introduce a v1, v2, vN construction each for the sphere keys and the migration, which truly feels a bit worse than utilizing uncooked strings. It’s over-complicated for positive, and it feels just like the schema definition is combined up with the precise question mechanism and the mannequin layer as properly.


Sorry people, I actually recognize the trouble that you have put into Fluent, however these points are actual and I do know that you could repair them on the long run and make the developer expertise lots higher.


Methods to make Fluent a bit higher?


On the brief time period I am attempting to repair these points and fortuitously there’s a good strategy to separate the question mechanism from the mannequin layer. It’s known as the repository sample and I would like to provide an enormous credit score to 0xTim once more, as a result of he made a cool reply on StackOverlow about this subject.


Anyway, the primary thought is that you just wrap the Request object right into a customized repository, it is normally a struct, then you definately solely name database associated queries inside this particular object. If we check out on the default venture template (you’ll be able to generate one by utilizing the vapor toolbox), we will simply create a brand new repository for the Todo fashions.


import Vapor
import Fluent

struct TodoRepository {
    var req: Request
    
    
    init(req: Request) {
        self.req = req
    }
    
    
    func question() -> QueryBuilder<Todo> {
        Todo.question(on: req.db)
    }
    
    
    func question(_ id: Todo.IDValue) -> QueryBuilder<Todo> {
        question().filter(.$id == id)
    }
    
    
    func question(_ ids: [Todo.IDValue]) -> QueryBuilder<Todo> {
        question().filter(.$id ~~ ids)
    }

    
    func listing() async throws -> [Todo] {
        attempt await question().all()
    }
    
    
    func get(_ id: Todo.IDValue) async throws -> Todo? {
        attempt await get([id]).first
    }

    
    func get(_ ids: [Todo.IDValue]) async throws -> [Todo] {
        attempt await question(ids).all()
    }

    
    func create(_ mannequin: Todo) async throws -> Todo {
        attempt await mannequin.create(on: req.db)
        return mannequin
    }
    
    
    func replace(_ mannequin: Todo) async throws -> Todo {
        attempt await mannequin.replace(on: req.db)
        return mannequin
    }

    
    func delete(_ id: Todo.IDValue) async throws {
        attempt await delete([id])
    }

    
    func delete(_ ids: [Todo.IDValue]) async throws {
        attempt await question(ids).delete()
    }
}


That is how we’re can manipulate Todo fashions, any more you do not have to make use of the static strategies on the mannequin itself, however you need to use an occasion of the repository to change your database rows. The repository may be hooked as much as the Request object by utilizing a typical sample. The simplest manner is to return a service each time you want it.


import Vapor

extension Request {
    
    var todo: TodoRepository {
        .init(req: self)
    }
}


After all this can be a very primary resolution and it pollutes the namespace beneath the Request object, I imply, if in case you have a lot of repositories this generally is a drawback, however first let me present you the way to refactor the controller by utilizing this straightforward technique. 🤓


import Vapor

struct TodoController: RouteCollection {

    func boot(routes: RoutesBuilder) throws {
        let todos = routes.grouped("todos")
        todos.get(use: index)
        todos.submit(use: create)
        todos.group(":todoID") { todo in
            todo.delete(use: delete)
        }
    }

    func index(req: Request) async throws -> [Todo] {
        attempt await req.todo.listing()
    }

    func create(req: Request) async throws -> Todo {
        let todo = attempt req.content material.decode(Todo.self)
        return attempt await req.todo.create(todo)
    }

    func delete(req: Request) async throws -> HTTPStatus {
        guard let id = req.parameters.get("todoID", as: Todo.IDValue.self) else {
            throw Abort(.notFound)
        }
        attempt await req.todo.delete(id)
        return .okay
    }
}


As you’ll be able to see this manner we had been capable of get rid of the Fluent dependency from the controller, and we will merely name the suitable technique utilizing the repository occasion. Nonetheless if you wish to unit check the controller it’s not potential to mock the repository, so we now have to determine one thing about that challenge. First we’d like some new protocols.


public protocol Repository {
    init(_ req: Request)
}

public protocol TodoRepository: Repository {
    func question() -> QueryBuilder<Todo>
    func question(_ id: Todo.IDValue) -> QueryBuilder<Todo>
    func question(_ ids: [Todo.IDValue]) -> QueryBuilder<Todo>
    func listing() async throws -> [Todo]
    func get(_ ids: [Todo.IDValue]) async throws -> [Todo]
    func get(_ id: Todo.IDValue) async throws -> Todo?
    func create(_ mannequin: Todo) async throws -> Todo
    func replace(_ mannequin: Todo) async throws -> Todo
    func delete(_ ids: [Todo.IDValue]) async throws
    func delete(_ id: Todo.IDValue) async throws
}


Subsequent we will outline a shared repository registry utilizing the Software extension. This registry will permit us to register repositories for given identifiers, we’ll use the RepositoryId struct for this objective. The RepositoryRegistry will be capable to return a manufacturing unit occasion with a reference to the required request and registry service, this manner we’re going to have the ability to create an precise Repository primarily based on the identifier. After all this entire ceremony may be prevented, however I needed to provide you with a generic resolution to retailer repositories beneath the req.repository namespace. 😅


public struct RepositoryId: Hashable, Codable {

    public let string: String
    
    public init(_ string: String) {
        self.string = string
    }
}

public closing class RepositoryRegistry {

    non-public let app: Software
    non-public var builders: [RepositoryId: ((Request) -> Repository)]

    fileprivate init(_ app: Software) {
        self.app = app
        self.builders = [:]
    }

    fileprivate func builder(_ req: Request) -> RepositoryFactory {
        .init(req, self)
    }
    
    fileprivate func make(_ id: RepositoryId, _ req: Request) -> Repository {
        guard let builder = builders[id] else {
            fatalError("Repository for id `(id.string)` shouldn't be configured.")
        }
        return builder(req)
    }
    
    public func register(_ id: RepositoryId, _ builder: @escaping (Request) -> Repository) {
        builders[id] = builder
    }
}

public struct RepositoryFactory {
    non-public var registry: RepositoryRegistry
    non-public var req: Request
    
    fileprivate init(_ req: Request, _ registry: RepositoryRegistry) {
        self.req = req
        self.registry = registry
    }

    public func make(_ id: RepositoryId) -> Repository {
        registry.make(id, req)
    }
}

public extension Software {

    non-public struct Key: StorageKey {
        typealias Worth = RepositoryRegistry
    }
    
    var repositories: RepositoryRegistry {
        if storage[Key.self] == nil {
            storage[Key.self] = .init(self)
        }
        return storage[Key.self]!
    }
}

public extension Request {
    
    var repositories: RepositoryFactory {
        utility.repositories.builder(self)
    }
}


As a developer you simply need to provide you with a brand new distinctive identifier and lengthen the RepositoryFactory along with your getter on your personal repository sort.


public extension RepositoryId {
    static let todo = RepositoryId("todo")
}

public extension RepositoryFactory {

    var todo: TodoRepository {
        guard let outcome = make(.todo) as? TodoRepository else {
            fatalError("Todo repository shouldn't be configured")
        }
        return outcome
    }
}


We are able to now register the FluentTodoRepository object, we simply need to rename the unique TodoRepository struct and conform to the protocol as an alternative.



public struct FluentTodoRepository: TodoRepository {
    var req: Request
    
    public init(_ req: Request) {
        self.req = req
    }
    
    func question() -> QueryBuilder<Todo> {
        Todo.question(on: req.db)
    }

    
}


app.repositories.register(.todo) { req in
    FluentTodoRepository(req)
}


We’re going to have the ability to get the repository by way of the req.repositories.todo property. You do not have to vary the rest contained in the controller file.


import Vapor

struct TodoController: RouteCollection {

    func boot(routes: RoutesBuilder) throws {
        let todos = routes.grouped("todos")
        todos.get(use: index)
        todos.submit(use: create)
        todos.group(":todoID") { todo in
            todo.delete(use: delete)
        }
    }

    func index(req: Request) async throws -> [Todo] {
        attempt await req.repositories.todo.listing()
    }

    func create(req: Request) async throws -> Todo {
        let todo = attempt req.content material.decode(Todo.self)
        return attempt await req.repositories.todo.create(todo)
    }

    func delete(req: Request) async throws -> HTTPStatus {
        guard let id = req.parameters.get("todoID", as: Todo.IDValue.self) else {
            throw Abort(.notFound)
        }
        attempt await req.repositories.todo.delete(id)
        return .okay
    }
}


The perfect a part of this strategy is that you could merely substitute the FluentTodoRepository with a MockTodoRepository for testing functions. I additionally like the truth that we do not pollute the req.* namespace, however each single repository has its personal variable beneath the repositories key.


You may provide you with a generic DatabaseRepository protocol with an related database Mannequin sort, then you might implement some primary options as a protocol extension for the Fluent fashions. I am utilizing this strategy and I am fairly proud of it thus far, what do you assume? Ought to the Vapor core crew add higher assist for repositories? Let me know on Twitter. ☺️




Related Articles

LEAVE A REPLY

Please enter your comment!
Please enter your name here

Latest Articles