From 0c480ac5a04b0c702401503830a726ee0ebca40e Mon Sep 17 00:00:00 2001
From: Javier Cicchelli <javier@rock-n-code.com>
Date: Sun, 16 Apr 2023 17:14:19 +0200
Subject: [PATCH] Implemented the Dependency property wrapper.

---
 .../Property Wrappers/Dependency.swift        | 31 ++++++++
 .../Property Wrappers/DependencyTests.swift   | 73 +++++++++++++++++++
 2 files changed, 104 insertions(+)
 create mode 100644 Sources/Dependencies/Property Wrappers/Dependency.swift
 create mode 100644 Tests/Dependencies/Property Wrappers/DependencyTests.swift

diff --git a/Sources/Dependencies/Property Wrappers/Dependency.swift b/Sources/Dependencies/Property Wrappers/Dependency.swift
new file mode 100644
index 0000000..ebe96fe
--- /dev/null
+++ b/Sources/Dependencies/Property Wrappers/Dependency.swift	
@@ -0,0 +1,31 @@
+//
+//  Dependency.swift
+//  Dependencies
+//
+//  Created by Javier Cicchelli on 11/04/2023.
+//  Copyright © 2023 Röck+Cöde. All rights reserved.
+//
+
+/// This property wrapper provides a direct connection to the `DependencyService` service.
+@propertyWrapper
+public struct Dependency<D> {
+    
+    // MARK: Properties
+    
+    private let keyPath: WritableKeyPath<DependencyService, D>
+    
+    /// This property allows direct read/write access to a defined dependency attached to a selected key path.
+    public var wrappedValue: D {
+        get { DependencyService[keyPath] }
+        set { DependencyService[keyPath] = newValue }
+    }
+    
+    // MARK: Initialisers
+    
+    /// Initialise the property wrapper by setting a key path to a defined dependency.
+    /// - Parameter keyPath: A key path to a defined dependency in the `DependencyService` service.
+    public init(_ keyPath: WritableKeyPath<DependencyService, D>) {
+        self.keyPath = keyPath
+    }
+
+}
diff --git a/Tests/Dependencies/Property Wrappers/DependencyTests.swift b/Tests/Dependencies/Property Wrappers/DependencyTests.swift
new file mode 100644
index 0000000..ce0e8fb
--- /dev/null
+++ b/Tests/Dependencies/Property Wrappers/DependencyTests.swift	
@@ -0,0 +1,73 @@
+//
+//  DependencyTests.swift
+//  DependenciesTests
+//
+//  Created by Javier Cicchelli on 11/04/2023.
+//  Copyright © 2023 Röck+Cöde. All rights reserved.
+//
+
+import Dependencies
+import XCTest
+
+final class DependencyTests: XCTestCase {
+    
+    // MARK: Properties
+    
+    private var subject: TestSubject!
+    
+    // MARK: Setup
+    
+    override func setUp() {
+        DependencyService[\.testService] = SomeService()
+    }
+    
+    // MARK: Tests
+
+    func test_readTestService() {
+        // GIVEN
+        subject = .init()
+        
+        // WHEN
+        let service = subject.testService
+        
+        // THEN
+        XCTAssertNotNil(service)
+        XCTAssert(service is SomeService)
+    }
+    
+    func test_writeDependencyKey() async throws {
+        // GIVEN
+        subject = .init()
+        
+        subject.testService = SomeOtherService()
+        
+        // WHEN
+        let service = DependencyService[\.testService]
+        
+        // THEN
+        XCTAssertNotNil(service)
+        XCTAssert(service is SomeOtherService)
+    }
+    
+    func test_writeDependencyKeyTwice() async throws {
+        // GIVEN
+        subject = .init()
+        
+        subject.testService = SomeOtherService()
+        subject.testService = SomeService()
+        
+        // WHEN
+        let service = DependencyService[\.testService]
+        
+        // THEN
+        XCTAssertNotNil(service)
+        XCTAssert(service is SomeService)
+    }
+
+}
+
+// MARK: - TestSubject
+
+private struct TestSubject {
+    @Dependency(\.testService) var testService
+}