Implemented the KeychainStorage dynamic property wrapper.

Libraries/Sources/KeychainStorage/Property Wrappers/KeychainStorage.swift

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+//
+//  KeychainStorage.swift
+//  KeychainStorage
+//
+//  Created by Javier Cicchelli on 11/12/2022.
+//  Copyright © 2022 Röck+Cöde. All rights reserved.
+//
+
+import Foundation
+import KeychainAccess
+import SwiftUI
+
+@propertyWrapper
+public struct KeychainStorage<Model: Codable>: DynamicProperty {
+    
+    // MARK: Type aliases
+    
+    public typealias Value = Model
+    
+    // MARK: States
+    
+    @State private var value: Value?
+    
+    // MARK: Properties
+    
+    private let key: String
+    private let keychain: Keychainable
+    private let decoder: JSONDecoder = .init()
+    private let encoder: JSONEncoder = .init()
+    
+    public var wrappedValue: Value? {
+        get { value }
+        nonmutating set {
+            value = newValue
+            
+            do {
+                if let newValue {
+                    let encodedValue = try encoder.encode(newValue)
+                    
+                    try keychain.set(encodedValue, key: key, ignoringAttributeSynchronizable: true)
+                } else {
+                    try keychain.remove(key, ignoringAttributeSynchronizable: true)
+                }
+            } catch {
+                assertionFailure("The '\(key)' key should have either be set or removed from the keychain storage.")
+            }
+        }
+    }
+    
+    public var projectedValue: Binding<Value?> {
+        .init { wrappedValue } set: { wrappedValue = $0 }
+    }
+    
+    // MARK: Initialisers
+    
+    public init(
+        key: String,
+        defaultValue: Value? = nil,
+        keychain: Keychainable = Keychain()
+    ) {
+        self.key = key
+        self.keychain = keychain
+        
+        do {
+            let data = try keychain.getData(key, ignoringAttributeSynchronizable: true)
+            
+            guard let data else {
+                assertionFailure("The data of the '\(key)' key should have been obtained from the keychain storage.")
+                return
+            }
+            
+            do {
+                let model = try decoder.decode(Value.self, from: data)
+                
+                self._value = .init(initialValue: model)
+            } catch {
+                assertionFailure("The data for the '\(key)' key should have been decoded properly.")
+            }
+        } catch {
+            self._value = .init(initialValue: defaultValue)
+        }
+    }
+    
+}

Libraries/Tests/KeychainStorageTests/Cases/Property Wrappers/KeychainStorage+InitTests.swift

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+//
+//  KeychainStorage+InitTests.swift
+//  KeychainStorageTests
+//
+//  Created by Javier Cicchelli on 11/12/2022.
+//  Copyright © 2022 Röck+Cöde. All rights reserved.
+//
+
+import Foundation
+import KeychainStorage
+import XCTest
+
+final class KeychainStorageInitTests: XCTestCase {
+    
+    // MARK: Properties
+    
+    private var value: TestModel?
+    
+    // MARK: Test cases
+    
+    func testValue_whenNoDefaultValue_andEmptyStorage() throws {
+        // GIVEN
+        let keychainStorage = TestKeychainStorage_withNoDefaultValue_andEmptyStorage()
+        
+        // WHEN
+        value = keychainStorage.keychainValue
+        
+        // THEN
+        XCTAssertNil(value)
+    }
+
+    func testValue_whenDefaultValue_andEmptyStorage() throws {
+        // GIVEN
+        let keychainStorage = TestKeychainStorage_withDefaultValue_andEmptyStorage()
+        
+        // WHEN
+        value = keychainStorage.keychainValue
+        
+        // THEN
+        XCTAssertNotNil(value)
+    }
+    
+    func testValue_whenNoDefaultValue_andValueInStorage() throws {
+        // GIVEN
+        let keychainStorage = TestKeychainStorage_withNoDefaultValue_andValueInStorage()
+        
+        // WHEN
+        value = keychainStorage.keychainValue
+        
+        // THEN
+        XCTAssertNotNil(value)
+    }
+    
+    func testValue_whenNoDefaultValue_andNoValueInStorage() throws {
+        // GIVEN
+        let keychainStorage = TestKeychainStorage_withNoDefaultValue_andNoValueInStorage()
+        
+        // WHEN
+        value = keychainStorage.keychainValue
+        
+        // THEN
+        XCTAssertNil(value)
+    }
+
+}
+
+// MARK: - Test classes
+
+private final class TestKeychainStorage_withNoDefaultValue_andEmptyStorage {
+    @KeychainStorage(
+        key: .Keys.someKey,
+        keychain: KeychainStorageMock()
+    )
+    var keychainValue: TestModel?
+}
+
+
+private final class TestKeychainStorage_withDefaultValue_andEmptyStorage {
+    @KeychainStorage(
+        key: .Keys.someKey,
+        defaultValue: TestModel(),
+        keychain: KeychainStorageMock()
+    )
+    var keychainValue: TestModel?
+}
+
+private final class TestKeychainStorage_withNoDefaultValue_andValueInStorage {
+    @KeychainStorage(
+        key: .Keys.someKey,
+        keychain: KeychainStorageMock(storage: [
+            .Keys.someKey: try! JSONEncoder().encode(TestModel())
+        ])
+    )
+    var keychainValue: TestModel?
+}
+
+private final class TestKeychainStorage_withNoDefaultValue_andNoValueInStorage {
+    @KeychainStorage(
+        key: .Keys.someKey,
+        keychain: KeychainStorageMock(storage: [
+            .Keys.someOtherKey: try! JSONEncoder().encode(TestModel())
+        ])
+    )
+    var keychainValue: TestModel?
+}

Libraries/Tests/KeychainStorageTests/Helpers/Extensions/String+KeychainStorageKeys.swift

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+//
+//  String+KeychainStorageKeys.swift
+//  KeychainStorageTests
+//
+//  Created by Javier Cicchelli on 11/12/2022.
+//  Copyright © 2022 Röck+Cöde. All rights reserved.
+//
+
+extension String {
+    enum Keys {
+        static let someKey = "com.rockncode.app.assignment.be-real.library.keychain-storage.test.key.some-key"
+        static let someOtherKey = "com.rockncode.app.assignment.be-real.library.keychain-storage.test.key.some-other-key"
+    }
+}

Libraries/Tests/KeychainStorageTests/Helpers/Mocks/KeychainStorageMock.swift

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+//
+//  KeychainStorageMock.swift
+//  KeychainStorageTests
+//
+//  Created by Javier Cicchelli on 11/12/2022.
+//  Copyright © 2022 Röck+Cöde. All rights reserved.
+//
+
+import Foundation
+import KeychainStorage
+
+class KeychainStorageMock {
+    
+    // MARK: Properties
+
+    private var storage: [String: Data]
+    private let concurrentQueue = DispatchQueue(
+        label: "com.rockncode.app.assignment.be-real.library.keychain-storage.test.queue.keychain-storage",
+        attributes: .concurrent
+    )
+    
+    // MARK: Initialisers
+    
+    init(storage: [String: Data] = [:]) {
+        self.storage = storage
+    }
+
+}
+
+// MARK: - Keychainable
+
+extension KeychainStorageMock: Keychainable {
+    func getData(
+        _ key: String,
+        ignoringAttributeSynchronizable: Bool
+    ) throws -> Data? {
+        var data: Data?
+        
+        try concurrentQueue.sync {
+            guard let dataValue = storage[key] else {
+                throw KeychainStorageMockError.keyIsNotDefined
+            }
+
+            data = dataValue
+        }
+        
+        return data
+    }
+    
+    func set(
+        _ value: Data,
+        key: String,
+        ignoringAttributeSynchronizable: Bool
+    ) throws {
+        concurrentQueue.async(flags: .barrier) {
+            self.storage[key] = value
+        }
+    }
+    
+    func remove(
+        _ key: String,
+        ignoringAttributeSynchronizable: Bool
+    ) throws {
+        guard storage.keys.contains(key) else {
+            throw KeychainStorageMockError.keyIsNotDefined
+        }
+        
+        concurrentQueue.async(flags: .barrier) {
+            self.storage.removeValue(forKey: key)
+        }
+    }
+}
+
+// MARK: - KeychainStorageSpyError
+
+enum KeychainStorageMockError: Error {
+    case keyIsNotDefined
+}

Libraries/Tests/KeychainStorageTests/Helpers/Models/TestModel.swift

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+//
+//  TestModel.swift
+//  KeychainStorageTests
+//
+//  Created by Javier Cicchelli on 11/12/2022.
+//  Copyright © 2022 Röck+Cöde. All rights reserved.
+//
+
+import Foundation
+
+struct TestModel: Codable, Equatable {
+    var uuid: String = UUID().uuidString
+    var text: String = "Some text goes in here..."
+    var number: Int = .random(in: 1 ... 100)
+    var boolean: Bool = .random()
+    var date: Date = .now
+}