Combine support for ApexyLoader (#30)

Documentation/loader.md

@@ -129,6 +129,34 @@ final class ProfileViewController: UIViewController {
 }
 ```
 
+## Observing loading state via Combine
+
+To keep track of the loader state via Combine use `statePublisher`.
+
+```swift
+final class ProfileViewController: UIViewController {
+    private var bag = Set<AnyCancellable>()
+    ...
+    override func viewDidLoad() {
+        super.viewDidLoad()
+        userProfileLoader.statePublisher.sink { [weak self] newState in
+            guard let self = self else { return }
+
+            switch newState {
+            case .initial:
+                //
+            case .loading(let cache):
+                //
+            case .success(let content):
+                //
+            case .failure(let error, let cache):
+                //
+            }
+        }.store(in: &bag)
+    }
+}
+```
+
 ## Use cases
 
 ApexyLoader used in the following scenarios:

Documentation/loader_ru.md

@@ -128,6 +128,34 @@ final class ProfileViewController: UIViewController {
 }
 ```
 
+## Отслеживание состояния загрузки через Combine
+
+Чтобы следить за состоянием загрузчика с помощью Combine используйте паблишер `statePublisher`.
+
+```swift
+final class ProfileViewController: UIViewController {
+    private var bag = Set<AnyCancellable>()
+    ...
+    override func viewDidLoad() {
+        super.viewDidLoad()
+        userProfileLoader.statePublisher.sink { [weak self] newState in
+            guard let self = self else { return }
+
+            switch newState {
+            case .initial:
+                //
+            case .loading(let cache):
+                //
+            case .success(let content):
+                //
+            case .failure(let error, let cache):
+                //
+            }
+        }.store(in: &bag)
+    }
+}
+```
+
 ## Сценарии использования
 
 ApexyLoader применяется когда:

Sources/ApexyLoader/ContentLoader.swift

@@ -1,3 +1,6 @@
+#if canImport(Combine)
+import Combine
+#endif
 import Foundation
 
 private final class StateChangeHandler {
@@ -28,11 +31,24 @@ open class ContentLoader<Content>: ObservableLoader {
     public var state: LoadingState<Content> = .initial {
         didSet {
             stateHandlers.forEach { $0.notify() }
+
+            if #available(macOS 10.15, iOS 13.0, watchOS 6.0, tvOS 13.0, *) {
+                stateSubject.send(state)
+            }
         }
     }
 
+    @available(iOS 13.0, macOS 10.15, watchOS 6.0, tvOS 13.0, *)
+    private lazy var stateSubject = CurrentValueSubject<LoadingState<Content>, Never>(.initial)
+
+    /// Content loading status. The default value is `.initial`.
+    ///
+    /// - Remark: To change state use `update(_:)`.
+    @available(iOS 13.0, macOS 10.15, watchOS 6.0, tvOS 13.0, *)
+    public lazy var statePublisher: AnyPublisher<LoadingState<Content>, Never> = stateSubject.eraseToAnyPublisher()
+
     public init() {}
-
+    
     // MARK: - ObservableLoader
 
     /// Starts state observing.

Tests/ApexyLoaderTests/ContentLoaderTests.swift

@@ -1,12 +1,16 @@
 @testable import ApexyLoader
+import Combine
 import XCTest
 
 final class ContentLoaderTests: XCTestCase {
 
     private var contentLoader: ContentLoader<Int>!
     private var numberOfChanges = 0
     private var observation: LoaderObservation!
-
+
+    private var bag = Set<AnyCancellable>()
+    private var receivedValues = [LoadingState<Int>]()
+
     override func setUp() {
         super.setUp()
 
@@ -15,7 +19,13 @@ final class ContentLoaderTests: XCTestCase {
         observation = contentLoader.observe { [weak self] in
             self?.numberOfChanges += 1
         }
-
+
+        receivedValues.removeAll()
+
+        contentLoader.statePublisher.sink(receiveCompletion: { _ in }) { loadingState in
+            self.receivedValues.append(loadingState)
+        }.store(in: &bag)
+
         XCTAssertTrue(
             contentLoader.observations.isEmpty,
             "No observation of other loaders")
@@ -32,6 +42,15 @@ final class ContentLoaderTests: XCTestCase {
             numberOfChanges, 0,
             "The change handler didn‘t triggered because the observation was canceled")
     }
+
+    func testCancelObservationCombine() {
+        bag.removeAll()
+        contentLoader.state = .success(content: 10)
+        XCTAssertEqual(
+            receivedValues,
+            [.initial],
+            "The change handler didn‘t triggered because the observation was canceled")
+    }
 
     func testStartLoading() {
         XCTAssertTrue(
@@ -54,12 +73,29 @@ final class ContentLoaderTests: XCTestCase {
             numberOfChanges, 1,
             "The change handler did NOT triggered")
     }
+
+    func testStartLoadingCombine() {
+        XCTAssertTrue(
+            contentLoader.startLoading(),
+            "Loading has begun")
+        XCTAssertEqual(
+            receivedValues,
+            [.initial, .loading(cache: nil)],
+            "State of the loader must be loading")
+        XCTAssertFalse(
+            contentLoader.startLoading(),
+            "The second loading didn‘t start before the end of the first one.")
+        XCTAssertEqual(
+            receivedValues,
+            [.initial, .loading(cache: nil)],
+            "The load status has NOT changed")
+    }
 
     func testFinishLoading() {
         contentLoader.finishLoading(.success(12))
         XCTAssertTrue(
             contentLoader.state == .success(content: 12),
-            "Succesfull loading state")
+            "Successfully loading state")
         XCTAssertEqual(
             numberOfChanges, 1,
             "The change handler triggered")
@@ -73,6 +109,24 @@ final class ContentLoaderTests: XCTestCase {
             numberOfChanges, 2,
             "The handler triggered")
     }
+
+    func testFinishLoadingCombine() {
+        contentLoader.finishLoading(.success(12))
+        XCTAssertEqual(
+            receivedValues,
+            [.initial, .success(content: 12)],
+            "Successfully loading state")
+
+        receivedValues.removeAll()
+
+        let error = URLError(.networkConnectionLost)
+        contentLoader.finishLoading(.failure(error))
+
+        XCTAssertEqual(
+            receivedValues,
+            [.failure(error: error, cache: 12)],
+            "The state must me failure with cache")
+    }
 
     func testUpdate() {
         contentLoader.update(.initial)
@@ -90,4 +144,24 @@ final class ContentLoaderTests: XCTestCase {
             numberOfChanges, 1,
             "The state didn't changed and the handler didn't triggered")
     }
+
+    func testUpdateCombine() {
+        contentLoader.update(.initial)
+        XCTAssertEqual(
+            receivedValues,
+            [.initial],
+            "The state didn't change and the handler didn't triggered")
+
+        contentLoader.update(.success(content: 1))
+        XCTAssertEqual(
+            receivedValues,
+            [.initial, .success(content: 1)],
+            "The state changed and the handler triggered")
+
+        contentLoader.update(.success(content: 1))
+        XCTAssertEqual(
+            receivedValues,
+            [.initial, .success(content: 1)],
+            "The state didn't changed and the handler didn't triggered")
+    }
 }