feat: Async init

Package.swift

@@ -1,4 +1,4 @@
-// swift-tools-version:5.5
+// swift-tools-version:5.8
 // The swift-tools-version declares the minimum version of Swift required to build this package.
 
 import PackageDescription
@@ -23,7 +23,8 @@ let package = Package(
             dependencies: [],
             path: "Sources",
             swiftSettings: [
-                .define("APPLICATION_EXTENSION_API_ONLY")
+                .define("APPLICATION_EXTENSION_API_ONLY"),
+                .enableUpcomingFeature("StrictConcurrency")
             ]
         ),
         .testTarget(

Sources/Container/AsyncContainer.swift

@@ -0,0 +1,154 @@
+//
+//  AsyncContainer.swift
+//  DependencyInjection
+//
+//  Created by Róbert Oravec on 17.12.2024.
+//
+
+import Foundation
+
+/// Dependency Injection Container where dependencies are registered and from where they are consequently retrieved (i.e. resolved)
+public actor AsyncContainer: AsyncDependencyResolving, AsyncDependencyRegistering {
+    /// Shared singleton
+    public static let shared: AsyncContainer = {
+        AsyncContainer()
+    }()
+
+    private var registrations = [RegistrationIdentifier: AsyncRegistration]()
+    private var sharedInstances = [RegistrationIdentifier: Any]()
+
+    /// Create new instance of ``Container``
+    public init() {}
+
+    /// Remove all registrations and already instantiated shared instances from the container
+    public func clean() {
+        registrations.removeAll()
+
+        releaseSharedInstances()
+    }
+
+    /// Remove already instantiated shared instances from the container
+    public func releaseSharedInstances() {
+        sharedInstances.removeAll()
+    }
+
+    // MARK: Register dependency, Autoregister dependency
+
+
+    /// Register a dependency
+    ///
+    /// - Parameters:
+    ///   - type: Type of the dependency to register
+    ///   - scope: Scope of the dependency. If `.new` is used, the `factory` closure is called on each `resolve` call. If `.shared` is used, the `factory` closure is called only the first time, the instance is cached and it is returned for all subsequent `resolve` calls, i.e. it is a singleton
+    ///   - factory: Closure that is called when the dependency is being resolved
+    public func register<Dependency>(
+        type: Dependency.Type,
+        in scope: DependencyScope,
+        factory: @escaping Factory<Dependency>
+    ) async {
+        let registration = AsyncRegistration(type: type, scope: scope, factory: factory)
+
+        registrations[registration.identifier] = registration
+
+        // With a new registration we should clean all shared instances
+        // because the new registered factory most likely returns different objects and we have no way to tell
+        sharedInstances[registration.identifier] = nil
+    }
+
+    // MARK: Register dependency with argument, Autoregister dependency with argument
+
+    /// Register a dependency with an argument
+    ///
+    /// The argument is typically a parameter in an initiliazer of the dependency that is not registered in the same container,
+    /// therefore, it needs to be passed in `resolve` call
+    ///
+    /// DISCUSSION: This registration method doesn't have any scope parameter for a reason.
+    /// The container should always return a new instance for dependencies with arguments as the behaviour for resolving shared instances with arguments is undefined.
+    /// Should the argument conform to ``Equatable`` to compare the arguments to tell whether a shared instance with a given argument was already resolved?
+    /// Shared instances are typically not dependent on variable input parameters by definition.
+    /// If you need to support this usecase, please, keep references to the variable singletons outside of the container.
+    ///
+    /// - Parameters:
+    ///   - type: Type of the dependency to register
+    ///   - factory: Closure that is called when the dependency is being resolved
+    public func register<Dependency, Argument>(type: Dependency.Type, factory: @escaping FactoryWithArgument<Dependency, Argument>) async {
+        let registration = AsyncRegistration(type: type, scope: .new, factory: factory)
+
+        registrations[registration.identifier] = registration
+    }
+
+    // MARK: Resolve dependency
+
+    /// Resolve a dependency that was previously registered with `register` method
+    ///
+    /// If a dependency of the given type with the given argument wasn't registered before this method call
+    /// the method throws ``ResolutionError.dependencyNotRegistered``
+    ///
+    /// - Parameters:
+    ///   - type: Type of the dependency that should be resolved
+    ///   - argument: Argument that will passed as an input parameter to the factory method that was defined with `register` method
+    public func tryResolve<Dependency: Sendable, Argument: Sendable>(type: Dependency.Type, argument: Argument) async throws -> Dependency {
+        let identifier = RegistrationIdentifier(type: type, argument: Argument.self)
+
+        let registration = try getRegistration(with: identifier)
+
+        let dependency: Dependency = try await getDependency(from: registration, with: argument)
+
+        return dependency
+    }
+
+    /// Resolve a dependency that was previously registered with `register` method
+    ///
+    /// If a dependency of the given type wasn't registered before this method call
+    /// the method throws ``ResolutionError.dependencyNotRegistered``
+    ///
+    /// - Parameters:
+    ///   - type: Type of the dependency that should be resolved
+    public func tryResolve<Dependency: Sendable>(type: Dependency.Type) async throws -> Dependency {
+        let identifier = RegistrationIdentifier(type: type)
+
+        let registration = try getRegistration(with: identifier)
+
+        let dependency: Dependency = try await getDependency(from: registration)
+
+        return dependency
+    }
+}
+
+// MARK: Private methods
+private extension AsyncContainer {
+    func getRegistration(with identifier: RegistrationIdentifier) throws -> AsyncRegistration {
+        guard let registration = registrations[identifier] else {
+            throw ResolutionError.dependencyNotRegistered(
+                message: "Dependency of type \(identifier.description) wasn't registered in container \(self)"
+            )
+        }
+
+        return registration
+    }
+
+    func getDependency<Dependency: Sendable>(from registration: AsyncRegistration, with argument: (any Sendable)? = nil) async throws -> Dependency {
+        switch registration.scope {
+        case .shared:
+            if let dependency = sharedInstances[registration.identifier] as? Dependency {
+                return dependency
+            }
+        case .new:
+            break
+        }
+
+        // We use force cast here because we are sure that the type-casting always succeed
+        // The reason why the `factory` closure returns ``Any`` is that we have to erase the generic type in order to store the registration
+        // When the registration is created it can be initialized just with a `factory` that returns the matching type
+        let dependency = try await registration.factory(self, argument) as! Dependency
+
+        switch registration.scope {
+        case .shared:
+            sharedInstances[registration.identifier] = dependency
+        case .new:
+            break
+        }
+
+        return dependency
+    }
+}

Sources/Container/Container.swift

@@ -8,7 +8,7 @@
 import Foundation
 
 /// Dependency Injection Container where dependencies are registered and from where they are consequently retrieved (i.e. resolved)
-open class Container: DependencyWithArgumentAutoregistering, DependencyAutoregistering, DependencyWithArgumentResolving {
+open class Container: DependencyWithArgumentAutoregistering, DependencyAutoregistering, DependencyWithArgumentResolving, @unchecked Sendable {
     /// Shared singleton
     public static let shared: Container = {
         Container()

Sources/Models/AsyncRegistration.swift

@@ -0,0 +1,39 @@
+//
+//  AsyncRegistration.swift
+//  DependencyInjection
+//
+//  Created by Róbert Oravec on 16.12.2024.
+//
+
+import Foundation
+
+typealias AsyncRegistrationFactory = @Sendable (any AsyncDependencyResolving, (any Sendable)?) async throws -> any Sendable
+
+/// Object that represents a registered dependency and stores a closure, i.e. a factory that returns the desired dependency
+struct AsyncRegistration: Sendable {
+    let identifier: RegistrationIdentifier
+    let scope: DependencyScope
+    let factory: AsyncRegistrationFactory
+
+    /// Initializer for registrations that don't need any variable argument
+    init<T: Sendable>(type: T.Type, scope: DependencyScope, factory: @Sendable @escaping (any AsyncDependencyResolving) async -> T) {
+        self.identifier = RegistrationIdentifier(type: type)
+        self.scope = scope
+        self.factory = { resolver, _ in await factory(resolver) }
+    }
+
+    /// Initializer for registrations that expect a variable argument passed to the factory closure when the dependency is being resolved
+    init<T: Sendable, Argument: Sendable>(type: T.Type, scope: DependencyScope, factory: @Sendable @escaping (any AsyncDependencyResolving, Argument) async -> T) {
+        let registrationIdentifier = RegistrationIdentifier(type: type, argument: Argument.self)
+
+        self.identifier = registrationIdentifier
+        self.scope = scope
+        self.factory = { resolver, arg in
+            guard let argument = arg as? Argument else {
+                throw ResolutionError.unmatchingArgumentType(message: "Registration of type \(registrationIdentifier.description) doesn't accept an argument of type \(Argument.self)")
+            }
+
+            return await factory(resolver, argument)
+        }
+    }
+}

Sources/Models/DependencyScope.swift

@@ -8,7 +8,7 @@
 import Foundation
 
 /// Scope of a dependency
-public enum DependencyScope {
+public enum DependencyScope: Sendable {
     /// A new instance of the dependency is created each time the dependency is resolved from the container.
     case new
 

Sources/Protocols/AsyncModuleRegistration.swift

@@ -0,0 +1,11 @@
+//
+//  ModileRegistration.swift
+//  DependencyInjection
+//
+//  Created by Róbert Oravec on 17.12.2024.
+//
+
+/// Protocol used to enforce common naming of registration in a module.
+public protocol AsyncModuleRegistration {
+    static func registerDependencies(in container: AsyncContainer) async
+}

Sources/Protocols/ModuleRegistration.swift

@@ -0,0 +1,11 @@
+//
+//  ModuleRegistration.swift
+//  DependencyInjection
+//
+//  Created by Róbert Oravec on 19.12.2024.
+//
+
+/// Protocol used to enforce common naming of registration in a module.
+public protocol ModuleRegistration {
+    static func registerDependencies(in container: Container)
+}

Sources/Protocols/Registration/AsyncDependencyRegistering.swift

@@ -0,0 +1,94 @@
+//
+//  AsyncDependencyRegistering.swift
+//  DependencyInjection
+//
+//  Created by Róbert Oravec on 17.12.2024.
+//
+
+import Foundation
+
+/// A type that is able to register a dependency
+public protocol AsyncDependencyRegistering {
+    /// Factory closure that instantiates the required dependency
+    typealias Factory<Dependency: Sendable> = @Sendable (any AsyncDependencyResolving) async -> Dependency
+
+    /// Factory closure that instantiates the required dependency with the given variable argument
+    typealias FactoryWithArgument<Dependency: Sendable, Argument: Sendable> = @Sendable (any AsyncDependencyResolving, Argument) async -> Dependency
+
+    /// Register a dependency
+    ///
+    /// - Parameters:
+    ///   - type: Type of the dependency to register
+    ///   - scope: Scope of the dependency. If `.new` is used, the `factory` closure is called on each `resolve` call. If `.shared` is used, the `factory` closure is called only the first time, the instance is cached and it is returned for all subsequent `resolve` calls, i.e. it is a singleton
+    ///   - factory: Closure that is called when the dependency is being resolved
+    func register<Dependency: Sendable>(type: Dependency.Type, in scope: DependencyScope, factory: @escaping Factory<Dependency>) async
+
+    /// Register a dependency with a variable argument
+    ///
+    /// The argument is typically a parameter in an initiliazer of the dependency that is not registered in the same resolver (i.e. container),
+    /// therefore, it needs to be passed in `resolve` call
+    ///
+    /// DISCUSSION: This registration method doesn't have any scope parameter for a reason.
+    /// The container should always return a new instance for dependencies with arguments as the behaviour for resolving shared instances with arguments is undefined.
+    /// Should the argument conform to ``Equatable`` to compare the arguments to tell whether a shared instance with a given argument was already resolved?
+    /// Shared instances are typically not dependent on variable input parameters by definition.
+    /// If you need to support this usecase, please, keep references to the variable singletons outside of the container.
+    ///
+    /// - Parameters:
+    ///   - type: Type of the dependency to register
+    ///   - factory: Closure that is called when the dependency is being resolved
+    func register<Dependency: Sendable, Argument: Sendable>(type: Dependency.Type, factory: @escaping FactoryWithArgument<Dependency, Argument>) async
+}
+
+// MARK: Overloaded factory methods
+public extension AsyncDependencyRegistering {
+    /// Default ``DependencyScope`` value
+    ///
+    /// The default value is `shared`
+    static var defaultScope: DependencyScope {
+        DependencyScope.shared
+    }
+
+    /// Register a dependency in the default ``DependencyScope``, i.e. in the `shared` scope
+    ///
+    /// - Parameters:
+    ///   - type: Type of the dependency to register
+    ///   - factory: Closure that is called when the dependency is being resolved
+    func register<Dependency: Sendable>(type: Dependency.Type, factory: @escaping Factory<Dependency>) async {
+        await register(type: type, in: Self.defaultScope, factory: factory)
+    }
+
+    /// Register a dependency with an implicit type determined by the factory closure return type
+    ///
+    /// - Parameters:
+    ///   - scope: Scope of the dependency. If `.new` is used, the `factory` closure is called on each `resolve` call. If `.shared` is used, the `factory` closure is called only the first time, the instance is cached and it is returned for all subsequent `resolve` calls, i.e. it is a singleton
+    ///   - factory: Closure that is called when the dependency is being resolved
+    func register<Dependency: Sendable>(in scope: DependencyScope, factory: @escaping Factory<Dependency>) async {
+        await register(type: Dependency.self, in: scope, factory: factory)
+    }
+
+    /// Register a dependency with an implicit type determined by the factory closure return type and in the default ``DependencyScope``, i.e. in the `shared` scope
+    ///
+    /// - Parameters:
+    ///   - factory: Closure that is called when the dependency is being resolved
+    func register<Dependency: Sendable>(factory: @escaping Factory<Dependency>) async {
+        await register(type: Dependency.self, in: Self.defaultScope, factory: factory)
+    }
+
+    /// Register a dependency with a variable argument. The type of the dependency is determined implicitly based on the factory closure return type
+    ///
+    /// The argument is typically a parameter in an initializer of the dependency that is not registered in the same resolver (i.e. container),
+    /// therefore, it needs to be passed in `resolve` call
+    ///
+    /// DISCUSSION: This registration method doesn't have any scope parameter for a reason.
+    /// The container should always return a new instance for dependencies with arguments as the behaviour for resolving shared instances with arguments is undefined.
+    /// Should the argument conform to ``Equatable`` to compare the arguments to tell whether a shared instance with a given argument was already resolved?
+    /// Shared instances are typically not dependent on variable input parameters by definition.
+    /// If you need to support this usecase, please, keep references to the variable singletons outside of the container.
+    ///
+    /// - Parameters:
+    ///   - factory: Closure that is called when the dependency is being resolved
+    func register<Dependency: Sendable, Argument: Sendable>(factory: @escaping FactoryWithArgument<Dependency, Argument>) async {
+        await register(type: Dependency.self, factory: factory)
+    }
+}