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Droplet

The Droplet is a service container that gives you access to many of Vapor's facilities. It is responsible for registering routes, starting the server, appending middleware, and more.

Tip

Normally applications will only have one Droplet. However, for advanced use cases, it is possible to create more than one.

Initialization

As you have probably already seen, the only thing required to create an instance of Droplet is to import Vapor.

import Vapor

let drop = try Droplet()

// your magic here

try drop.run()

Creation of the Droplet normally happens in the main.swift file.

Note

For the sake of simplicity, most of the documentations sample code uses just the main.swift file. You can read more about packages and modules in the Swift Package Manager conceptual overview.

Environment

The environment is accessible via the config of the droplet. It contains the current environment your application is running in. Usually development, testing, or production.

if drop.config.environment == .production {
    ...
}

The environment affects Config and Logging. The environment is development by default. To change it, pass the --env= flag as an argument.

vapor run serve --env=production

If you are in Xcode, you can pass arguments through the scheme editor.

Warning

Debug logs can reduce the number of requests your application can handle per second. Enable production mode to silence non-critical logs.

Config Directory

The workDir property contains a path to the current working directory of the application. Vapor uses this property to find the folders related to your project, such as Resources, Public, and Config.

print(drop.workDir) // /var/www/my-project/

Vapor automatically determines the working directory in most situations. However, you may need to manually set it for advanced use cases.

You can override the working directory through the Droplet's initializer, or by passing the --workdir argument.

vapor run serve --workdir="/var/www/my-project"

Modifying Properties

The Droplet's properties can be changed programmatically or through configuration.

Programmatic

Properties on the Droplet are constant and can be overridden through the init method.

let drop = try Droplet(server: MyServerType.self)

Here the type of server the Droplet uses is changed to a custom type. When the Droplet is run, this custom server type will be booted instead of the default server.

Warning

Using the init method manually can override configured properties.

Configurable

If you want to modify a property of the Droplet only in certain cases, you can use addConfigurable. Say for example you want to email error logs to yourself in production, but you don't want to spam your inbox while developing.

let config = try Config()
config.addConfigurable(log: MyEmailLogger.init, name: "email")

let drop = Droplet(config)

The Droplet will continue to use the default logger until you modify the Config/droplet.json file to point to your email logger. If this is done in Config/production/droplet.json, then your logger will only be used in production.

{
    "log": "email"
}

Supported Properties

Property Type droplet.json key Config Initializable
server ServerProtocol.Type server no
client ClientProtocol.Type client no
log LogProtocol log yes
hash HashProtocol hash yes
cipher CipherProtocol cipher yes
middleware Middleware middleware.[server,client] no
console ConsoleProtocol console yes
cache CacheProtocol cache yes

Example

Let's create a custom logger to demonstrate Vapor's configurable properties.

AllCapsLogger.swift

final class AllCapsLogger: LogProtocol {
    var enabled: [LogLevel] = []
    func log(_ level: LogLevel, message: String, file: String, function: String, line: Int) {
        print(message.uppercased + "!!!")
    }
}

Now add the logger to the Droplet using the addConfigurable method for logs.

main.swift

let config = try Config()
config.addConfigurable(log: AllCapsLogger(), name: "all-caps")

let drop = try Droplet(config)

Whenever the "log" property is set to "all-caps" in the droplet.json, our new logger will be used.

Config/development/droplet.json

{
    "log": "all-caps"
}

Here we are setting our logger only in the development environment. All other environments will use Vapor's default logger.

Config Initializable

For an added layer of convenience, you can allow your custom types to be initialized from configuration files.

In our previous example, we initialized an AllCapsLogger before adding it to the Droplet.

Let's say we want to allow our project to configure how many exclamation points get added with each log message.

AllCapsLogger.swift

final class AllCapsLogger: LogProtocol {
    var enabled: [LogLevel] = []
    let exclamationCount: Int

    init(exclamationCount: Int) {
        self.exclamationCount = exclamationCount
    }

    func log(_ level: LogLevel, message: String, file: String, function: String, line: Int) {
        print(message.uppercased + String(repeating: "!", count: exclamationCount))
    }
}

extension AllCapsLogger: ConfigInitializable {
   init(config: Config) throws {
        let count = config["allCaps", "exclamationCount"]?.int ?? 3
        self.init(exclamationCount: count)
   } 
}

Note

The first parameter to config is the name of the file.

Now that we have conformed our logger to ConfigInitializable, we can pass just the type name to addConfigurable.

main.swift

let config = try Config()
config.addConfigurable(log: AllCapsLogger.self, name: "all-caps")

let drop = try Droplet(config)

Now if you add a file named allCaps.json to the Config folder, you can configure the logger.

allCaps.json

{
    "exclamationCount": 5
}

With this configurable abstraction, you can easily change how your application functions in different environments without needing to hard code these values into your source code.