I’ve written a number of articles about manufacturing facility design patterns on my weblog and this time I would like to speak a couple of particular one, which you’ll encounter in the event you work with Vapor. Here is slightly recap about my manufacturing facility design sample weblog posts, all written in Swift:
Now let’s dive in to the “Fluent sample”. So as to perceive this structure, first we should always study the associated Swift packages first. There may be the FluentKit library and several other Fluent database driver implementations (SQLite, PostgreSQL, MySQL, and so on.), all primarily based on the FluentKit product. Additionally there may be one bundle that connects Fluent with Vapor, this one is just known as: Fluent. 📀
- FluentKit – comprises the summary interface (with out Vapor, utilizing SwiftNIO)
- Fluent[xy]Driver – comprises the implementation outlined in FluentKit
- Fluent – connects FluentKit with Vapor, by extending Vapor
That is the bottom construction, the FluentKit library gives the next summary interfaces, which you need to implement if you wish to create your personal driver implementation. Sadly you will not have the ability to discover correct documentation for these interfaces, so I will clarify them a bit:
- Database – Question execution and transaction associated capabilities
- DatabaseContext – Holds the config, logger, occasion loop, historical past and web page dimension restrict
- DatabaseDriver – A manufacturing facility interface to create and shutdown Database cases
- DatabaseID – A singular ID to retailer database configs, drivers and cases
- DatabaseError – A generic database associated error protocol
- DatabaseConfiguration – A protocol to create DatabaseDriver objects
- DatabaseConfigurationFactory – A box-like object to cover driver associated stuff
- Databases – Shared config, driver and working occasion storage
As you possibly can see there are various protocols concerned on this structure, however I will attempt to stroll you thru the complete driver creation circulation and hopefully you’ll perceive how the items are associated, and the way can construct your personal drivers and even Vapor parts primarily based on this.
Fluent is written as a service for Vapor utilizing the underlying shared storage object, that is what shops a reference to the Databases occasion. This object has two hash maps, for storing configurations and working driver cases utilizing the DatabaseID as a key for each. 🔑
Whenever you ask for a driver, the Databases object will examine if that driver exists, if sure, it will merely return it and story over. The attention-grabbing half occurs when the motive force doesn’t exists but within the Databases storage. First the system will examine for a pre-registered driver implementation.
app.databases.use(.sqlite(.file("db.sqlite")), as: .sqlite)This line above registers a brand new driver configuration for the shared Databases. The .sqlite() methodology is a static operate on the DatabaseConfigurationFactory which creates a brand new SQLite particular configuration and hides it utilizing the init(make:) name. The SQLite associated configuration implements the DatabaseConfiguration protocol, so it may be used as a sound config when the system creates the precise database context.
The config object can be accountable for creating the particular driver object utilizing the Databases object if wanted. At this level we have got a configuration and a driver occasion registered within the databases storage. What occurs if somebody asks for a database occasion?
Relying on the context, you possibly can ask for a Database implementation by the app.db or req.db properties. That is outlined within the FluentProvider code and behind the scenes all the things may be traced again to the Databases class. Because you solely wish to have a single shared storage for all of the drivers, however you additionally wish to keep away from the singleton sample, you need to hook this service as much as the Utility class. That is how the Vapor of us did it anyway. 🤓
let db: Database = req.db
let db: Database = req.db(.sqlite)
let db: Database = app.db
let db: Database = app.db(.sqlite)Whenever you ask for a database, or a database with an specific identifier, you’re basically calling a make methodology contained in the Databases class, which goes search for a registered configuration and a driver implementation utilizing the hashes and it will name the motive force’s make methodology and move across the logger, the occasion loop and the present database configuration as a database context object.
We will say that after you ask for an summary Database driver, a brand new DatabaseDriver occasion reference (related to a given DatabaseID) can be saved contained in the Databases class and it will at all times make you a brand new Database reference with the present DatabaseContext. If the motive force already exists, then it will be reused, however you continue to get new Database references (with the related context) each time. So, you will need to be aware that there’s just one DatabaseDriver occasion per configuration / database identifier, however it will possibly create a number of Database objects. 🤔
Okay, I do know, it is fairly sophisticated, however this is an oversimplified model in Swift:
ultimate class Databases {
var configs: [DatabaseID: DatabaseConfiguration] = [:]
var drivers: [DatabaseID: DatabaseDriver] = [:]
func make(
_ id: DatabaseID,
logger: Logger,
on eventLoop: EventLoop
) -> Database {
let config = configs[id]!
if drivers[id] == nil {
drivers[id] = config.make(self)
}
let context = DatabaseContext(config, logger, eventLoop)
return drivers[id]!.make(context)
}
func use(_ config: DatabaseConfiguration, for id: DatabaseID) {
configs[id] = config
}
}And the Vapor service extension may very well be interpreted considerably like this:
extension Utility {
var databases: Databases {
get {
if storage[DatabasesKey.self] == nil {
storage[DatabasesKey.self] = .init()
}
return storage[DatabasesKey.self]
}
set {
self.storage[MyConfigurationKey.self] = newValue
}
}
var db: Database {
databases.make(
.default,
logger: logger,
eventLoop: eventLoopGroup.subsequent()
)
}
}You possibly can apply the identical ideas and create an extension over the Request object to entry a Database occasion. After all there’s much more occurring beneath the hood, however the goal of this text is to get a primary overview of this sample, so I am not going into these particulars now. 🙃
Actually I actually like this strategy, as a result of it is elegant and it will possibly utterly cover driver particular particulars by these abstractions. I adopted the very same ideas once I created the Liquid file storage driver for Vapor and discovered quite a bit through the course of. Though, you need to be aware that not all the things is an effective candidate for being carried out an “summary Vapor service manufacturing facility” design sample (or no matter we name this strategy). Anyway, I actually hope that this fast tutorial will assist you to to create your personal Vapor parts, if wanted. 🤷♂️
