Vend preferredContentSize through the DescribedViewController

swift/WorkflowUI/Sources/ViewControllerDescription/DescribedViewController.swift

@@ -52,6 +52,7 @@ public final class DescribedViewController: UIViewController {
                 view.addSubview(currentViewController.view)
                 currentViewController.view.frame = view.bounds
                 currentViewController.didMove(toParent: self)
+                preferredContentSize = currentViewController.preferredContentSize
             }
         }
     }
@@ -66,6 +67,7 @@ public final class DescribedViewController: UIViewController {
         addChild(currentViewController)
         view.addSubview(currentViewController.view)
         currentViewController.didMove(toParent: self)
+        preferredContentSize = currentViewController.preferredContentSize
     }
 
     public override func viewDidLayoutSubviews() {
@@ -93,6 +95,16 @@ public final class DescribedViewController: UIViewController {
         return currentViewController.supportedInterfaceOrientations
     }
 
+    public override func preferredContentSizeDidChange(forChildContentContainer container: UIContentContainer) {
+        super.preferredContentSizeDidChange(forChildContentContainer: container)
+
+        guard
+            (container as? UIViewController) == currentViewController,
+            container.preferredContentSize != preferredContentSize
+        else { return }
+
+        preferredContentSize = container.preferredContentSize
+    }
 }
 
 #endif

swift/WorkflowUI/Tests/DescribedViewControllerTests.swift

@@ -0,0 +1,334 @@
+/*
+ * Copyright 2020 Square Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#if canImport(UIKit)
+
+import XCTest
+
+import ReactiveSwift
+import Workflow
+@testable import WorkflowUI
+
+class DescribedViewControllerTests: XCTestCase {
+
+    // MARK: - Tests
+
+    func test_init() {
+        // Given
+        let screen = TestScreen.counter(0)
+
+        // When
+        let describedViewController = DescribedViewController(screen: screen, environment: .empty)
+
+        // Then
+        guard
+            let currentViewController = describedViewController.currentViewController as? CounterViewController
+        else {
+            XCTFail("Expected a \(String(reflecting: CounterViewController.self)), but got:  \(describedViewController.currentViewController)")
+            return
+        }
+
+        XCTAssertEqual(currentViewController.count, 0)
+        XCTAssertFalse(describedViewController.isViewLoaded)
+        XCTAssertFalse(currentViewController.isViewLoaded)
+        XCTAssertNil(currentViewController.parent)
+    }
+
+    func test_viewDidLoad() {
+        // Given
+        let screen = TestScreen.counter(0)
+        let describedViewController = DescribedViewController(screen: screen, environment: .empty)
+
+        // When
+        _ = describedViewController.view
+
+        // Then
+        XCTAssertEqual(describedViewController.currentViewController.parent, describedViewController)
+        XCTAssertNotNil(describedViewController.currentViewController.viewIfLoaded?.superview)
+    }
+
+    func test_update_toCompatibleDescription_beforeViewLoads() {
+        // Given
+        let screenA = TestScreen.counter(0)
+        let screenB = TestScreen.counter(1)
+
+        let describedViewController = DescribedViewController(screen: screenA, environment: .empty)
+        let initialChildViewController = describedViewController.currentViewController
+
+        // When
+        describedViewController.update(screen: screenB, environment: .empty)
+
+        // Then
+        XCTAssertEqual(initialChildViewController, describedViewController.currentViewController)
+        XCTAssertEqual((describedViewController.currentViewController as? CounterViewController)?.count, 1)
+        XCTAssertFalse(describedViewController.isViewLoaded)
+        XCTAssertFalse(describedViewController.currentViewController.isViewLoaded)
+        XCTAssertNil(describedViewController.currentViewController.parent)
+    }
+
+    func test_update_toCompatibleDescription_afterViewLoads() {
+        // Given
+        let screenA = TestScreen.counter(0)
+        let screenB = TestScreen.counter(1)
+
+        let describedViewController = DescribedViewController(screen: screenA, environment: .empty)
+        let initialChildViewController = describedViewController.currentViewController
+
+        // When
+        _ = describedViewController.view
+        describedViewController.update(screen: screenB, environment: .empty)
+
+        // Then
+        XCTAssertEqual(initialChildViewController, describedViewController.currentViewController)
+        XCTAssertEqual((describedViewController.currentViewController as? CounterViewController)?.count, 1)
+    }
+
+    func test_update_toIncompatibleDescription_beforeViewLoads() {
+        // Given
+        let screenA = TestScreen.counter(0)
+        let screenB = TestScreen.message("Test")
+
+        let describedViewController = DescribedViewController(screen: screenA, environment: .empty)
+        let initialChildViewController = describedViewController.currentViewController
+
+        // When
+        describedViewController.update(screen: screenB, environment: .empty)
+
+        // Then
+        XCTAssertNotEqual(initialChildViewController, describedViewController.currentViewController)
+        XCTAssertEqual((describedViewController.currentViewController as? MessageViewController)?.message, "Test")
+        XCTAssertFalse(describedViewController.isViewLoaded)
+        XCTAssertFalse(describedViewController.currentViewController.isViewLoaded)
+        XCTAssertNil(describedViewController.currentViewController.parent)
+    }
+
+    func test_update_toIncompatibleDescription_afterViewLoads() {
+        // Given
+        let screenA = TestScreen.counter(0)
+        let screenB = TestScreen.message("Test")
+
+        let describedViewController = DescribedViewController(screen: screenA, environment: .empty)
+        let initialChildViewController = describedViewController.currentViewController
+
+        // When
+        _ = describedViewController.view
+        describedViewController.update(screen: screenB, environment: .empty)
+
+        // Then
+        XCTAssertNotEqual(initialChildViewController, describedViewController.currentViewController)
+        XCTAssertEqual((describedViewController.currentViewController as? MessageViewController)?.message, "Test")
+        XCTAssertNil(initialChildViewController.parent)
+        XCTAssertEqual(describedViewController.currentViewController.parent, describedViewController)
+        XCTAssertNil(initialChildViewController.viewIfLoaded?.superview)
+        XCTAssertNotNil(describedViewController.currentViewController.viewIfLoaded?.superview)
+    }
+
+    func test_childViewControllerFor() {
+        // Given
+        let screen = TestScreen.counter(0)
+
+        let describedViewController = DescribedViewController(screen: screen, environment: .empty)
+        let currentViewController = describedViewController.currentViewController
+
+        // When, Then
+        XCTAssertEqual(describedViewController.childForStatusBarStyle, currentViewController)
+        XCTAssertEqual(describedViewController.childForStatusBarHidden, currentViewController)
+        XCTAssertEqual(describedViewController.childForHomeIndicatorAutoHidden, currentViewController)
+        XCTAssertEqual(describedViewController.childForScreenEdgesDeferringSystemGestures, currentViewController)
+        XCTAssertEqual(describedViewController.supportedInterfaceOrientations, currentViewController.supportedInterfaceOrientations)
+    }
+
+    func test_childViewControllerFor_afterIncompatibleUpdate() {
+        // Given
+        let screenA = TestScreen.counter(0)
+        let screenB = TestScreen.message("Test")
+
+        let describedViewController = DescribedViewController(screen: screenA, environment: .empty)
+        let initialChildViewController = describedViewController.currentViewController
+
+        describedViewController.update(screen: screenB, environment: .empty)
+        let currentViewController = describedViewController.currentViewController
+
+        // When, Then
+        XCTAssertNotEqual(initialChildViewController, currentViewController)
+        XCTAssertEqual(describedViewController.childForStatusBarStyle, currentViewController)
+        XCTAssertEqual(describedViewController.childForStatusBarHidden, currentViewController)
+        XCTAssertEqual(describedViewController.childForHomeIndicatorAutoHidden, currentViewController)
+        XCTAssertEqual(describedViewController.childForScreenEdgesDeferringSystemGestures, currentViewController)
+        XCTAssertEqual(describedViewController.supportedInterfaceOrientations, currentViewController.supportedInterfaceOrientations)
+    }
+
+    func test_preferredContentSizeDidChange() {
+        // Given
+        let screenA = TestScreen.counter(1)
+        let screenB = TestScreen.counter(2)
+
+        let describedViewController = DescribedViewController(screen: screenA, environment: .empty)
+        let containerViewController = ContainerViewController(describedViewController: describedViewController)
+
+        // When
+        let expectation = self.expectation(description: "did observe size changes")
+        expectation.expectedFulfillmentCount = 2
+
+        var observedSizes: [CGSize] = []
+        let disposable = containerViewController.preferredContentSizeSignal.observeValues {
+            observedSizes.append($0)
+            expectation.fulfill()
+        }
+
+        defer { disposable?.dispose() }
+
+        _ = containerViewController.view
+        describedViewController.update(screen: screenB, environment: .empty)
+
+        // Then
+        let expectedSizes = [CGSize(width: 10, height: 0), CGSize(width: 20, height: 0)]
+        waitForExpectations(timeout: 1, handler: nil)
+        XCTAssertEqual(observedSizes, expectedSizes)
+    }
+
+    func test_preferredContentSizeDidChange_afterIncompatibleUpdate() {
+        // Given
+        let screenA = TestScreen.counter(1)
+        let screenB = TestScreen.message("Test")
+        let screenC = TestScreen.message("Testing")
+
+        let describedViewController = DescribedViewController(screen: screenA, environment: .empty)
+        let containerViewController = ContainerViewController(describedViewController: describedViewController)
+
+        // When
+        let expectation = self.expectation(description: "did observe size changes")
+        expectation.expectedFulfillmentCount = 3
+
+        var observedSizes: [CGSize] = []
+        let disposable = containerViewController.preferredContentSizeSignal.observeValues {
+            observedSizes.append($0)
+            expectation.fulfill()
+        }
+
+        defer { disposable?.dispose() }
+
+        _ = containerViewController.view
+        describedViewController.update(screen: screenB, environment: .empty)
+        describedViewController.update(screen: screenC, environment: .empty)
+
+        // Then
+        let expectedSizes = [
+            CGSize(width: 10, height: 0),
+            CGSize(width: 40, height: 0),
+            CGSize(width: 70, height: 0),
+        ]
+
+        waitForExpectations(timeout: 1, handler: nil)
+        XCTAssertEqual(observedSizes, expectedSizes)
+    }
+}
+
+// MARK: - Helper Types
+
+fileprivate enum TestScreen: Screen, Equatable {
+    case counter(Int)
+    case message(String)
+
+    func viewControllerDescription(environment: ViewEnvironment) -> ViewControllerDescription {
+        switch self {
+        case let .counter(count):
+            return ViewControllerDescription(
+                build: { CounterViewController(count: count) },
+                update: { $0.count = count }
+            )
+
+        case let .message(message):
+            return ViewControllerDescription(
+                build: { MessageViewController(message: message) },
+                update: { $0.message = message }
+            )
+        }
+    }
+}
+
+fileprivate class ContainerViewController: UIViewController {
+    let describedViewController: DescribedViewController
+
+    var preferredContentSizeSignal: Signal<CGSize, Never> { return signal.skipRepeats() }
+
+    private let (signal, sink) = Signal<CGSize, Never>.pipe()
+
+    init(describedViewController: DescribedViewController) {
+        self.describedViewController = describedViewController
+        super.init(nibName: nil, bundle: nil)
+    }
+
+    @available(*, unavailable) required init?(coder: NSCoder) {
+        fatalError("init(coder:) has not been implemented")
+    }
+
+    override func viewDidLoad() {
+        super.viewDidLoad()
+
+        addChild(describedViewController)
+        describedViewController.view.frame = view.bounds
+        describedViewController.view.autoresizingMask = [.flexibleWidth, .flexibleHeight]
+        view.addSubview(describedViewController.view)
+        describedViewController.didMove(toParent: self)
+    }
+
+    override func preferredContentSizeDidChange(forChildContentContainer container: UIContentContainer) {
+        super.preferredContentSizeDidChange(forChildContentContainer: container)
+
+        guard container === describedViewController else { return }
+
+        sink.send(value: container.preferredContentSize)
+    }
+}
+
+fileprivate class CounterViewController: UIViewController {
+    var count: Int {
+        didSet {
+            preferredContentSize.width = CGFloat(count * 10)
+        }
+    }
+
+    init(count: Int) {
+        self.count = count
+        super.init(nibName: nil, bundle: nil)
+        preferredContentSize.width = CGFloat(count * 10)
+    }
+
+    @available(*, unavailable) required init?(coder: NSCoder) {
+        fatalError("init(coder:) has not been implemented")
+    }
+}
+
+fileprivate class MessageViewController: UIViewController {
+    var message: String {
+        didSet {
+            preferredContentSize.width = CGFloat(message.count * 10)
+        }
+    }
+
+    init(message: String) {
+        self.message = message
+        super.init(nibName: nil, bundle: nil)
+        preferredContentSize.width = CGFloat(message.count * 10)
+    }
+
+    @available(*, unavailable) required init?(coder: NSCoder) {
+        fatalError("init(coder:) has not been implemented")
+    }
+}
+
+#endif