BaseChatViewController calls update for reused presenters

appsailor · Aug 1, 2019 · cdbc86b · cdbc86b
1 parent e4de8db
commit cdbc86b
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Showing 6 changed files with 87 additions and 12 deletions.
diff --git a/Chatto/Source/Chat Items/BaseChatItemPresenter.swift b/Chatto/Source/Chat Items/BaseChatItemPresenter.swift
@@ -35,6 +35,15 @@ open class BaseChatItemPresenter<CellT: UICollectionViewCell>: ChatItemPresenter
 
     public init() {}
 
+    open var isItemUpdateSupported: Bool {
+        assertionFailure("Implement in subclass")
+        return false
+    }
+
+    open func update(with chatItem: ChatItemProtocol) {
+        assertionFailure("Implement in subclass")
+    }
+
     open class func registerCells(_ collectionView: UICollectionView) {
         assert(false, "Implement in subclass")
     }

diff --git a/Chatto/Source/Chat Items/ChatItemProtocolDefinitions.swift b/Chatto/Source/Chat Items/ChatItemProtocolDefinitions.swift
@@ -43,6 +43,10 @@ public protocol ChatItemMenuPresenterProtocol {
 
 public protocol ChatItemPresenterProtocol: AnyObject, ChatItemMenuPresenterProtocol {
     static func registerCells(_ collectionView: UICollectionView)
+
+    var isItemUpdateSupported: Bool { get }
+    func update(with chatItem: ChatItemProtocol)
+
     var canCalculateHeightInBackground: Bool { get } // Default is false
     func heightForCell(maximumWidth width: CGFloat, decorationAttributes: ChatItemDecorationAttributesProtocol?) -> CGFloat
     func dequeueCell(collectionView: UICollectionView, indexPath: IndexPath) -> UICollectionViewCell

diff --git a/Chatto/Source/Chat Items/DummyChatItemPresenter.swift b/Chatto/Source/Chat Items/DummyChatItemPresenter.swift
@@ -24,13 +24,21 @@
 
 import Foundation
 
-// Handles messages that aren't supported so they appear as invisible
+// Handles messages which aren't supported. So, they appear as invisible.
 class DummyChatItemPresenter: ChatItemPresenterProtocol {
 
     class func registerCells(_ collectionView: UICollectionView) {
         collectionView.register(DummyCollectionViewCell.self, forCellWithReuseIdentifier: "cell-id-unhandled-message")
     }
 
+    var isItemUpdateSupported: Bool {
+        return true
+    }
+
+    func update(with chatItem: ChatItemProtocol) {
+        // Does nothing
+    }
+
     var canCalculateHeightInBackground: Bool {
         return true
     }

diff --git a/Chatto/Source/ChatController/BaseChatViewController+Changes.swift b/Chatto/Source/ChatController/BaseChatViewController+Changes.swift
@@ -317,6 +317,11 @@ extension BaseChatViewController {
                     return self.createPresenterForChatItem(decoratedChatItem.chatItem)
                 }
 
+                guard oldChatItemCompanion.presenter.isItemUpdateSupported else {
+                    return self.createPresenterForChatItem(decoratedChatItem.chatItem)
+                }
+
+                oldChatItemCompanion.presenter.update(with: decoratedChatItem.chatItem)
                 return oldChatItemCompanion.presenter
             }()
 

diff --git a/Chatto/Tests/ChatController/BaseChatViewControllerTestHelpers.swift b/Chatto/Tests/ChatController/BaseChatViewControllerTestHelpers.swift
@@ -83,14 +83,16 @@ class FakeDataSource: ChatDataSourceProtocol {
 class FakeCell: UICollectionViewCell {}
 
 class FakePresenterBuilder: ChatItemPresenterBuilderProtocol {
-    var presentersCreatedCount: Int = 0
+    private(set) var createdPresenters: [ChatItemPresenterProtocol] = []
+
     func canHandleChatItem(_ chatItem: ChatItemProtocol) -> Bool {
         return chatItem.type == "fake-type"
     }
 
     func createPresenterWithChatItem(_ chatItem: ChatItemProtocol) -> ChatItemPresenterProtocol {
-        self.presentersCreatedCount += 1
-        return FakePresenter()
+        let presenter = FakePresenter()
+        self.createdPresenters.append(presenter)
+        return presenter
     }
 
     var presenterType: ChatItemPresenterProtocol.Type {
@@ -99,6 +101,20 @@ class FakePresenterBuilder: ChatItemPresenterBuilderProtocol {
 }
 
 class FakePresenter: BaseChatItemPresenter<FakeCell> {
+
+    var _isItemUpdateSupportedReturnValue: Bool = false
+    override var isItemUpdateSupported: Bool {
+        return self._isItemUpdateSupportedReturnValue
+    }
+
+    private var _updateWithChatItemCalls: [(ChatItemProtocol)] = []
+    var _updateWithChatItemIsCalled: Bool { return self._updateWithChatItemCallsCount > 0 }
+    var _updateWithChatItemCallsCount: Int { return self._updateWithChatItemCalls.count }
+    var _updateWithChatItemLastCallParams: ChatItemProtocol? { return self._updateWithChatItemCalls.last }
+    override func update(with chatItem: ChatItemProtocol) {
+        self._updateWithChatItemCalls.append((chatItem))
+    }
+
     override class func registerCells(_ collectionView: UICollectionView) {
         collectionView.register(FakeCell.self, forCellWithReuseIdentifier: "fake-cell")
     }
@@ -131,6 +147,8 @@ final class FakeChatItem: ChatItemProtocol {
 
 final class FakeChatItemPresenter: ChatItemPresenterProtocol {
     init() {}
+    var isItemUpdateSupported: Bool { return false }
+    func update(with chatItem: ChatItemProtocol) {}
     static func registerCells(_ collectionView: UICollectionView) {}
     func heightForCell(maximumWidth width: CGFloat, decorationAttributes: ChatItemDecorationAttributesProtocol?) -> CGFloat { return 0 }
     func dequeueCell(collectionView: UICollectionView, indexPath: IndexPath) -> UICollectionViewCell { return UICollectionViewCell() }

diff --git a/Chatto/Tests/ChatController/BaseChatViewControllerTests.swift b/Chatto/Tests/ChatController/BaseChatViewControllerTests.swift
@@ -67,7 +67,7 @@ class ChatViewControllerTests: XCTestCase {
         fakeDataSource.chatItems = createFakeChatItems(count: 2)
         controller.chatDataSource = fakeDataSource
         self.fakeDidAppearAndLayout(controller: controller)
-        XCTAssertEqual(2, presenterBuilder.presentersCreatedCount)
+        XCTAssertEqual(2, presenterBuilder.createdPresenters.count)
     }
 
     func testThat_WhenDataSourceChanges_ThenCollectionViewUpdatesAsynchronously() {
@@ -285,7 +285,8 @@ extension ChatViewControllerTests {
         fakeDataSource.chatItems = createFakeChatItems(count: 2)
         controller.chatDataSource = fakeDataSource
         self.fakeDidAppearAndLayout(controller: controller)
-        XCTAssertEqual(presenterBuilder.presentersCreatedCount, 2)
+        presenterBuilder.createdPresenters.forEach { ($0 as! FakePresenter)._isItemUpdateSupportedReturnValue = true }
+        let numberOfPresentersBeforeUpdate = presenterBuilder.createdPresenters.count
 
         fakeDataSource.chatItems = createFakeChatItems(count: 3)
         let asyncExpectation = expectation(description: "update")
@@ -294,27 +295,57 @@ extension ChatViewControllerTests {
         }
 
         self.waitForExpectations(timeout: 1) { _ in
-            XCTAssertEqual(presenterBuilder.presentersCreatedCount, 3)
+            let numberOfPresenterAfterUpdate = presenterBuilder.createdPresenters.count
+            XCTAssertEqual(numberOfPresenterAfterUpdate - numberOfPresentersBeforeUpdate, 1)
         }
     }
 
-    func testThat_WhenDataSourceIsUpdatedWithTheSameItems_ThenNoNewItemPresentersAreCreated() {
+    func testThat_GivenPresenterSupportsUpdates_WhenDataSourceIsUpdatedWithTheSameItem_ThendNewPresenterIsNotCreated_AndPresenterIsUpdatedOnce() {
         let presenterBuilder = FakePresenterBuilder()
         let controller = TesteableChatViewController(presenterBuilders: ["fake-type": [presenterBuilder]])
         let fakeDataSource = FakeDataSource()
-        fakeDataSource.chatItems = createFakeChatItems(count: 2)
+        fakeDataSource.chatItems = createFakeChatItems(count: 1)
         controller.chatDataSource = fakeDataSource
         self.fakeDidAppearAndLayout(controller: controller)
-        XCTAssertEqual(presenterBuilder.presentersCreatedCount, 2)
+        let presenter = presenterBuilder.createdPresenters.last! as! FakePresenter
+        presenter._isItemUpdateSupportedReturnValue = true
+        XCTAssertEqual(presenter._updateWithChatItemCallsCount, 0)
+        XCTAssertEqual(presenterBuilder.createdPresenters.count, 1)
 
-        fakeDataSource.chatItems = createFakeChatItems(count: 2)
+        fakeDataSource.chatItems = createFakeChatItems(count: 1)
         let asyncExpectation = expectation(description: "update")
         controller.enqueueModelUpdate(updateType: .normal) {
             asyncExpectation.fulfill()
         }
 
         self.waitForExpectations(timeout: 1) { _ in
-            XCTAssertEqual(presenterBuilder.presentersCreatedCount, 2)
+            XCTAssertEqual(presenterBuilder.createdPresenters.count, 1)
+            XCTAssertEqual(presenter._updateWithChatItemCallsCount, 1)
+            XCTAssert(presenter._updateWithChatItemLastCallParams! === fakeDataSource.chatItems.first!)
         }
     }
+
+    func testThat_GivenPresenterDoesntSupportUpdates_WhenDataSourceIsUpdatedWithTheSameItem_ThenPresenterIsNotUpdated_AndNewPresenterIsCreated() {
+            let presenterBuilder = FakePresenterBuilder()
+            let controller = TesteableChatViewController(presenterBuilders: ["fake-type": [presenterBuilder]])
+            let fakeDataSource = FakeDataSource()
+            fakeDataSource.chatItems = createFakeChatItems(count: 1)
+            controller.chatDataSource = fakeDataSource
+            self.fakeDidAppearAndLayout(controller: controller)
+            let presenter = presenterBuilder.createdPresenters.last! as! FakePresenter
+            presenter._isItemUpdateSupportedReturnValue = false
+            XCTAssertEqual(presenter._updateWithChatItemCallsCount, 0)
+            XCTAssertEqual(presenterBuilder.createdPresenters.count, 1)
+
+            fakeDataSource.chatItems = createFakeChatItems(count: 1)
+            let asyncExpectation = expectation(description: "update")
+            controller.enqueueModelUpdate(updateType: .normal) {
+                asyncExpectation.fulfill()
+            }
+
+            self.waitForExpectations(timeout: 1) { _ in
+                XCTAssertFalse(presenter._updateWithChatItemIsCalled)
+                XCTAssertEqual(presenterBuilder.createdPresenters.count, 2)
+            }
+        }
 }