refactor: improve implementation

Sources/DependencyInjection/Container.swift

@@ -25,7 +25,7 @@
 import Foundation
 
 /// A dependency injection container that manages the creation and resolution of services.
-public final class Container: DIContainerProtocol {
+public final class Container {
     /// A shared instance of the container, accessible throughout the application.
     public static var shared = Container()
     /// A lock to ensure thread safety during registration and resolution.
@@ -41,7 +41,7 @@ public final class Container: DIContainerProtocol {
     ///   - factory: A closure that creates an instance of the service when needed.
     public func register<T>(
         _ instanceType: InstanceType = .transient,
-        to type: T.Type = T.self,
+        to type: T.Type,
         factory: @escaping (Container) -> T
     ) {
         lock.lock()
@@ -55,7 +55,7 @@ public final class Container: DIContainerProtocol {
     ///   - instanceType: The lifetime of the service instance (defaults to `transient`).
     ///   - type: The type of the service being registered (defaults to inferred type).
     ///   - value: An autoclosure that provides the service instance's value.
-    public func register<T>(_ instanceType: InstanceType = .transient, to type: T.Type = T.self, value: @escaping @autoclosure () -> T) {
+    public func register<T>(_ instanceType: InstanceType = .transient, to type: T.Type, value: @escaping @autoclosure () -> T) {
         lock.lock()
         defer { lock.unlock() }
         let factory: (Container) -> T = { _ in value() }
@@ -66,7 +66,7 @@ public final class Container: DIContainerProtocol {
     ///
     /// - Parameter type: The type of the service to resolve.
     /// - Returns: The resolved service instance, or nil if not registered.
-    public func resolve<T>(_ type: T.Type = T.self) -> T? {
+    public func resolve<T>(_ type: T.Type) -> T? {
         lock.lock()
         defer { lock.unlock() }
         let value: T? = storage[ServiceKey(type: type)]?.value(in: self)
@@ -79,8 +79,8 @@ public final class Container: DIContainerProtocol {
     ///
     /// - Parameter type: The type of the service to resolve.
     /// - Returns: The resolved service instance.
-    public func resolveRequired<T>(_ type: T.Type = T.self) -> T {
-        guard let unwrapped: T = resolve() else {
+    public func resolveRequired<T>(_ type: T.Type) -> T {
+        guard let unwrapped: T = resolve(type) else {
             preconditionFailure("Unable to resolve service of type \(T.self). It is not registered.")
         }
         return unwrapped

Sources/DependencyInjection/Inject.swift

@@ -42,6 +42,6 @@ public final class Inject<Service> {
     public init() {}
     /// Resolves the service from the specified container.
     private func resolve(in container: Container) -> Service {
-        container.resolveRequired() // Obtain the service from the container
+        container.resolveRequired(Service.self) // Obtain the service from the container
     }
 }

Sources/DependencyInjection/Service.swift

@@ -59,14 +59,9 @@ internal final class Service {
     /// - Parameter container: The container used for resolving dependencies (if needed).
     /// - Returns: The resolved service instance as Any.
     private func fetchValue(from container: Container) -> Any {
-        instance ?? create(in: container)
-    }
-
-    /// Creates a new instance of the service using the factory closure.
-    ///
-    /// - Parameter container: The container used for resolving dependencies (if needed).
-    /// - Returns: The newly created service instance.
-    private func create(in container: Container) -> Any {
+        if let instance = instance {
+            return instance
+        }
         let value = factory(container)
         if type == .singleton { instance = value }
         return value

Sources/DependencyInjection/ServiceKey.swift

@@ -25,7 +25,7 @@
 import Foundation
 
 /// A key used for storing and retrieving services within the dependency injection container.
-struct ServiceKey: Hashable {
+internal struct ServiceKey: Hashable {
     /// The type of the service associated with the key.
     let type: Any.Type
 

Tests/DependencyInjectionTests/ContainerTests.swift

@@ -34,15 +34,16 @@ final class ContainerTests: XCTestCase {
         container = .shared
     }
 
-    func testRegisterFactoryAndResolveTransient() {
+    func testRegisterFactoryAndResolveTransient() throws {
         container.register(.transient, to: MockService.self) { _ in
             MockService()
         }
 
-        let instance1 = container.resolve(MockService.self)
-        let instance2 = container.resolve(MockService.self)
+        let instance1 = try XCTUnwrap(container.resolve(MockService.self))
+        let instance2 = try XCTUnwrap(container.resolve(MockService.self))
 
         XCTAssertNotEqual(instance1, instance2)
+        XCTAssertTrue(type(of: instance1) === type(of: instance2))
     }
 
     func testRegisterFactoryAndResolveSingleton() {
@@ -53,7 +54,7 @@ final class ContainerTests: XCTestCase {
         let instance1 = container.resolve(MockService.self)
         let instance2 = container.resolve(MockService.self)
 
-        XCTAssertEqual(instance1, instance2)
+        XCTAssertTrue(instance1 === instance2)
     }
 
     func testRegisterValueAndResolveTransient() {
@@ -79,7 +80,7 @@ final class ContainerTests: XCTestCase {
     }
 }
 
-public class MockService: Equatable {
+internal class MockService: Equatable {
     var id = UUID()
     public var didCallFoo = false
     public var didCallBar = false

Tests/DependencyInjectionTests/InjectTests.swift

@@ -40,7 +40,7 @@ final class InjectTests: XCTestCase {
         @Inject var service: MockService
         @Inject var service1: MockService
 
-        XCTAssertEqual(service, service1)
+        XCTAssertTrue(service === service1)
     }
 
     func testInjectTransient() {
@@ -50,5 +50,6 @@ final class InjectTests: XCTestCase {
         @Inject var service1: MockService
 
         XCTAssertNotEqual(service, service1)
+        XCTAssertTrue(type(of: service) === type(of: service1))
     }
 }