🔌 Plug and Play

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🔌 Plug and Play

Plugin is a Swift SPM project that provides a flexible and modular approach to enhancing object functionality through the use of plugins. By conforming to the Plugin protocol, custom plugins can be created and added to objects that conform to the Pluginable protocol, without having to modify their original implementation. This allows developers the ability to add custom behaviors to their objects in a plug-and-play manner, making it easy to maintain and extend code over time.


Creating a plugin

To create a plugin, create a struct or class that conforms to the Plugin protocol and implement its requirements.

Here's an example of a simple plugin that adds an auth header to a URLRequest object:

struct AuthPlugin: Plugin {
    var keyPath: WritableKeyPath<PluginURLRequest, URLRequest>

    func handle(value: Void, output: inout URLRequest) async throws {
        output.allHTTPHeaderFields = ["auth": "token"]

Making an object pluginable

To use plugins with an object, make it conform to the Pluginable protocol. Here's an example of a PluginURLRequest class that can have plugins added to it:

class PluginURLRequest: Pluginable {
    var plugins: [any Plugin] = []

    var request: URLRequest

    init(url: URL) {
        self.request = URLRequest(url: url)

Registering and handling plugins

Plugins can be registered to a Pluginable object using the register(plugin: any Plugin) method. Once registered, the handle(value: Any) method can be called on the object to apply the registered plugins to it.

let urlRequest = PluginURLRequest(url: URL(string: "")!)

urlRequest.register(plugin: AuthPlugin(keyPath: \.request))

try await urlRequest.handle()
print(urlRequest.request.allHTTPHeaderFields) // ["auth": "token"]

Additional Features

You can also access the inputType and outputType properties of any plugin and get the list of plugins with their inputType and outputType properties.

let authPlugin = AuthPlugin(keyPath: \.request)
print(authPlugin.inputType) // Void
print(authPlugin.outputType) // URLRequest

let pluginTypes = urlRequest.pluginTypes
print(pluginTypes) // [(input: Void, output: URLRequest)]

Projects Using Plugins

  • Scribe: Scribe is a flexible logging library for Swift, designed to make logging easy and efficient. It provides a centralized system for logging messages and events within your application, and supports multiple logging outputs and plugins to extend its capabilities to meet your needs. Scribe integrates with swift-log for console logging, making it a versatile solution for all your logging requirements.

  • PluginTask: PluginTask is a custom Task that allows users to add plugins to modify its behavior. Plugins can be added to the PluginTask instance to perform additional functionality before or after the task's main operation. This makes it easy to modify the task's behavior without modifying its original implementation.


  • Swift Tools 5.6.0
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Last updated: Sun Mar 10 2024 00:25:55 GMT-1000 (Hawaii-Aleutian Standard Time)