Implement additional Single Selection APIs (#127)

Issue #94

Add `shouldSelect`, `shouldDeselect`, `didDeselect()`

CHANGELOG.md

@@ -10,8 +10,9 @@ NEXT
 0.1.7
 -----
 
-- Upgrade to Xcode 16. ([@jessesquires](https://github.com/jessesquires), [#116](https://github.com/jessesquires/ReactiveCollectionsKit/pull/116))
+- Upgraded to Xcode 16. ([@jessesquires](https://github.com/jessesquires), [#116](https://github.com/jessesquires/ReactiveCollectionsKit/pull/116))
 - Reverted back to Swift 5 language mode because of issues in UIKit. ([@jessesquires](https://github.com/jessesquires), [#116](https://github.com/jessesquires/ReactiveCollectionsKit/pull/116))
+- Implemented additional selection APIs for `CellViewModel`: `shouldSelect`, `shouldDeselect`, `didDeselect()`. ([@nuomi1](https://github.com/nuomi1), [#127](https://github.com/jessesquires/ReactiveCollectionsKit/pull/127))
 
 0.1.6
 -----

Example/Sources/Grid/GridViewController.swift

@@ -68,6 +68,10 @@ final class GridViewController: ExampleViewController, CellEventCoordinator {
         assertionFailure("unhandled cell selection")
     }
 
+    func didDeselectCell(viewModel: any CellViewModel) {
+        print("\(#function): \(viewModel.id)")
+    }
+
     // MARK: Private
 
     private static func makeLayout() -> UICollectionViewCompositionalLayout {
@@ -129,7 +133,8 @@ final class GridViewController: ExampleViewController, CellEventCoordinator {
 
             return PersonCellViewModelGrid(
                 person: $0,
-                contextMenuConfiguration: menuConfig
+                contextMenuConfiguration: menuConfig,
+                shouldSelect: false
             ).eraseToAnyViewModel()
         }
         let peopleHeader = HeaderViewModel(title: "People", style: .large)

Example/Sources/Grid/PersonCellViewModelGrid.swift

@@ -30,19 +30,24 @@ struct PersonCellViewModelGrid: CellViewModel {
 
     let contextMenuConfiguration: UIContextMenuConfiguration?
 
+    let shouldSelect: Bool
+
     func configure(cell: GridPersonCell) {
         cell.titleLabel.text = self.person.name
         cell.subtitleLabel.text = self.person.birthDateText
         cell.flagLabel.text = self.person.nationality
+        cell.contentView.alpha = self.shouldSelect ? 1 : 0.3
     }
 
     // MARK: Hashable
 
     nonisolated func hash(into hasher: inout Hasher) {
         hasher.combine(self.person)
+        hasher.combine(self.shouldSelect)
     }
 
     nonisolated static func == (left: Self, right: Self) -> Bool {
         left.person == right.person
+        && left.shouldSelect == right.shouldSelect
     }
 }

Sources/CellEventCoordinator.swift

@@ -22,6 +22,10 @@ public protocol CellEventCoordinator: AnyObject {
     /// - Parameter viewModel: The cell view model that corresponds to the cell.
     func didSelectCell(viewModel: any CellViewModel)
 
+    /// Called when a cell is deselected.
+    /// - Parameter viewModel: The cell view model that corresponds to the cell.
+    func didDeselectCell(viewModel: any CellViewModel)
+
     /// Returns the underlying view controller that owns the collection view for the cell.
     ///
     /// You may use this to optionally handle navigation within your cell view model.
@@ -33,6 +37,9 @@ extension CellEventCoordinator {
     /// Default implementation. Does nothing.
     public func didSelectCell(viewModel: any CellViewModel) { }
 
+    /// Default implementation. Does nothing.
+    public func didDeselectCell(viewModel: any CellViewModel) { }
+
     /// Default implementation. Returns `nil`.
     public var underlyingViewController: UIViewController? { nil }
 }

Sources/CellViewModel.swift

@@ -20,6 +20,16 @@ public protocol CellViewModel: DiffableViewModel, ViewRegistrationProvider {
     /// The type of cell that this view model represents and configures.
     associatedtype CellType: UICollectionViewCell
 
+    /// Returns whether or not the cell should get selected.
+    /// This corresponds to the delegate method `collectionView(_:shouldSelectItemAt:)`.
+    /// The default implementation returns `true`.
+    var shouldSelect: Bool { get }
+
+    /// Returns whether or not the cell should get deselected.
+    /// This corresponds to the delegate method `collectionView(_:shouldDeselectItemAt:)`.
+    /// The default implementation returns `true`.
+    var shouldDeselect: Bool { get }
+
     /// Returns whether or not the cell should get highlighted.
     /// This corresponds to the delegate method `collectionView(_:shouldHighlightItemAt:)`.
     /// The default implementation returns `true`.
@@ -33,10 +43,20 @@ public protocol CellViewModel: DiffableViewModel, ViewRegistrationProvider {
     /// - Parameter cell: The cell to configure.
     func configure(cell: CellType)
 
-    /// Handles the selection event for this cell, optionally using the provided `coordinator`.
+    /// Tells the view model that its cell was selected.
+    ///
+    /// Implement this method to handle this event, optionally using the provided `coordinator`.
+    ///
     /// - Parameter coordinator: An event coordinator object, if one was provided to the `CollectionViewDriver`.
     func didSelect(with coordinator: CellEventCoordinator?)
 
+    /// Tells the view model that its cell was deselected.
+    ///
+    /// Implement this method to handle this event, optionally using the provided `coordinator`.
+    ///
+    /// - Parameter coordinator: An event coordinator object, if one was provided to the `CollectionViewDriver`.
+    func didDeselect(with coordinator: CellEventCoordinator?)
+
     /// Tells the view model that its cell is about to be displayed in the collection view.
     /// This corresponds to the delegate method `collectionView(_:willDisplay:forItemAt:)`.
     func willDisplay()
@@ -55,6 +75,12 @@ public protocol CellViewModel: DiffableViewModel, ViewRegistrationProvider {
 }
 
 extension CellViewModel {
+    /// Default implementation. Returns `true`.
+    public var shouldSelect: Bool { true }
+
+    /// Default implementation. Returns `true`.
+    public var shouldDeselect: Bool { true }
+
     /// Default implementation. Returns `true`.
     public var shouldHighlight: Bool { true }
 
@@ -68,6 +94,13 @@ extension CellViewModel {
         coordinator?.didSelectCell(viewModel: self)
     }
 
+    /// Default implementation.
+    /// Calls `didDeselectCell(viewModel:)` on the `coordinator`,
+    /// passing `self` to the `viewModel` parameter.
+    public func didDeselect(with coordinator: CellEventCoordinator?) {
+        coordinator?.didDeselectCell(viewModel: self)
+    }
+
     /// Default implementation. Does nothing.
     public func willDisplay() { }
 
@@ -136,6 +169,12 @@ public struct AnyCellViewModel: CellViewModel {
     /// :nodoc:
     public typealias CellType = UICollectionViewCell
 
+    /// :nodoc:
+    public var shouldSelect: Bool { self._shouldSelect }
+
+    /// :nodoc:
+    public var shouldDeselect: Bool { self._shouldDeselect }
+
     /// :nodoc:
     public var shouldHighlight: Bool { self._shouldHighlight }
 
@@ -152,6 +191,11 @@ public struct AnyCellViewModel: CellViewModel {
         self._didSelect(coordinator)
     }
 
+    /// :nodoc:
+    public func didDeselect(with coordinator: CellEventCoordinator?) {
+        self._didDeselect(coordinator)
+    }
+
     /// :nodoc:
     public func willDisplay() {
         self._willDisplay()
@@ -183,10 +227,13 @@ public struct AnyCellViewModel: CellViewModel {
     private let _viewModel: AnyHashable
     private let _id: UniqueIdentifier
     private let _registration: ViewRegistration
+    private let _shouldSelect: Bool
+    private let _shouldDeselect: Bool
     private let _shouldHighlight: Bool
     private let _contextMenuConfiguration: UIContextMenuConfiguration?
     private let _configure: (CellType) -> Void
     private let _didSelect: (CellEventCoordinator?) -> Void
+    private let _didDeselect: (CellEventCoordinator?) -> Void
     private let _willDisplay: () -> Void
     private let _didEndDisplaying: () -> Void
     private let _didHighlight: () -> Void
@@ -205,6 +252,8 @@ public struct AnyCellViewModel: CellViewModel {
         self._viewModel = viewModel
         self._id = viewModel.id
         self._registration = viewModel.registration
+        self._shouldSelect = viewModel.shouldSelect
+        self._shouldDeselect = viewModel.shouldDeselect
         self._shouldHighlight = viewModel.shouldHighlight
         self._contextMenuConfiguration = viewModel.contextMenuConfiguration
         self._configure = { cell in
@@ -214,6 +263,7 @@ public struct AnyCellViewModel: CellViewModel {
         self._didSelect = { coordinator in
             viewModel.didSelect(with: coordinator)
         }
+        self._didDeselect = viewModel.didDeselect
         self._willDisplay = viewModel.willDisplay
         self._didEndDisplaying = viewModel.didEndDisplaying
         self._didHighlight = viewModel.didHighlight

Sources/CollectionViewDriver.swift

@@ -288,12 +288,30 @@ public final class CollectionViewDriver: NSObject {
 extension CollectionViewDriver: UICollectionViewDelegate {
     // MARK: Managing the selected cells
 
+    /// :nodoc:
+    public func collectionView(_ collectionView: UICollectionView,
+                               shouldSelectItemAt indexPath: IndexPath) -> Bool {
+        self.viewModel.cellViewModel(at: indexPath).shouldSelect
+    }
+
     /// :nodoc:
     public func collectionView(_ collectionView: UICollectionView,
                                didSelectItemAt indexPath: IndexPath) {
         self.viewModel.cellViewModel(at: indexPath).didSelect(with: self._cellEventCoordinator)
     }
 
+    /// :nodoc:
+    public func collectionView(_ collectionView: UICollectionView,
+                               shouldDeselectItemAt indexPath: IndexPath) -> Bool {
+        self.viewModel.cellViewModel(at: indexPath).shouldDeselect
+    }
+
+    /// :nodoc:
+    public func collectionView(_ collectionView: UICollectionView,
+                               didDeselectItemAt indexPath: IndexPath) {
+        self.viewModel.cellViewModel(at: indexPath).didDeselect(with: self._cellEventCoordinator)
+    }
+
     // MARK: Managing cell highlighting
 
     /// :nodoc:

Tests/Fakes/FakeCellEventCoordinator.swift

@@ -23,4 +23,11 @@ final class FakeCellEventCoordinator: CellEventCoordinator {
         self.selectedCell = viewModel
         self.expectationDidSelect?.fulfillAndLog()
     }
+
+    var deselectedCell: (any CellViewModel)?
+    var expectationDidDeselect: XCTestExpectation?
+    func didDeselectCell(viewModel: any CellViewModel) {
+        self.deselectedCell = viewModel
+        self.expectationDidDeselect?.fulfillAndLog()
+    }
 }

Tests/Fakes/FakeCellNibView.swift

@@ -44,6 +44,11 @@ struct FakeCellNibViewModel: CellViewModel {
         self.expectationDidSelect?.fulfillAndLog()
     }
 
+    var expectationDidDeselect: XCTestExpectation?
+    func didDeelect(with coordinator: (any CellEventCoordinator)?) {
+        self.expectationDidDeselect?.fulfillAndLog()
+    }
+
     var expectationWillDisplay: XCTestExpectation?
     func willDisplay() {
         self.expectationWillDisplay?.fulfillAndLog()

Tests/Fakes/FakeCollectionViewModel.swift

@@ -140,6 +140,7 @@ extension XCTestCase {
         if useNibs {
             var viewModel = FakeCellNibViewModel(id: id)
             viewModel.expectationDidSelect = self._expectation(expectationFields, target: .didSelect, id: viewModel.id, function: function)
+            viewModel.expectationDidDeselect = self._expectation(expectationFields, target: .didDeselect, id: viewModel.id, function: function)
             viewModel.expectationConfigureCell = self._expectation(expectationFields, target: .configure, id: viewModel.id, function: function)
             viewModel.expectationWillDisplay = self._expectation(expectationFields, target: .willDisplay, id: viewModel.id, function: function)
             viewModel.expectationDidEndDisplaying = self._expectation(expectationFields, target: .didEndDisplaying, id: viewModel.id, function: function)
@@ -151,6 +152,7 @@ extension XCTestCase {
         if cellIndex.isMultiple(of: 2) {
             var viewModel = FakeNumberCellViewModel(model: .init(id: id))
             viewModel.expectationDidSelect = self._expectation(expectationFields, target: .didSelect, id: viewModel.id, function: function)
+            viewModel.expectationDidDeselect = self._expectation(expectationFields, target: .didDeselect, id: viewModel.id, function: function)
             viewModel.expectationConfigureCell = self._expectation(expectationFields, target: .configure, id: viewModel.id, function: function)
             viewModel.expectationWillDisplay = self._expectation(expectationFields, target: .willDisplay, id: viewModel.id, function: function)
             viewModel.expectationDidEndDisplaying = self._expectation(expectationFields, target: .didEndDisplaying, id: viewModel.id, function: function)
@@ -161,6 +163,7 @@ extension XCTestCase {
 
         var viewModel = FakeTextCellViewModel(model: .init(text: id))
         viewModel.expectationDidSelect = self._expectation(expectationFields, target: .didSelect, id: viewModel.id, function: function)
+        viewModel.expectationDidDeselect = self._expectation(expectationFields, target: .didDeselect, id: viewModel.id, function: function)
         viewModel.expectationConfigureCell = self._expectation(expectationFields, target: .configure, id: viewModel.id, function: function)
         viewModel.expectationWillDisplay = self._expectation(expectationFields, target: .willDisplay, id: viewModel.id, function: function)
         viewModel.expectationDidEndDisplaying = self._expectation(expectationFields, target: .didEndDisplaying, id: viewModel.id, function: function)

Tests/Fakes/FakeNumberModel.swift

@@ -32,6 +32,10 @@ struct FakeNumberCellViewModel: CellViewModel {
         self.model.id
     }
 
+    var shouldSelect = true
+
+    var shouldDeselect = true
+
     var shouldHighlight = true
 
     var contextMenuConfiguration: UIContextMenuConfiguration?
@@ -46,6 +50,11 @@ struct FakeNumberCellViewModel: CellViewModel {
         self.expectationDidSelect?.fulfillAndLog()
     }
 
+    var expectationDidDeselect: XCTestExpectation?
+    func didDeselect(with coordinator: (any CellEventCoordinator)?) {
+        self.expectationDidDeselect?.fulfillAndLog()
+    }
+
     var expectationWillDisplay: XCTestExpectation?
     func willDisplay() {
         self.expectationWillDisplay?.fulfillAndLog()
@@ -66,8 +75,18 @@ struct FakeNumberCellViewModel: CellViewModel {
         self.expectationDidUnhighlight?.fulfillAndLog()
     }
 
-    init(model: FakeNumberModel = FakeNumberModel()) {
+    init(
+        model: FakeNumberModel = FakeNumberModel(),
+        shouldSelect: Bool = true,
+        shouldDeselect: Bool = true,
+        shouldHighlight: Bool = true,
+        contextMenuConfiguration: UIContextMenuConfiguration? = nil
+    ) {
         self.model = model
+        self.shouldSelect = shouldSelect
+        self.shouldDeselect = shouldDeselect
+        self.shouldHighlight = shouldHighlight
+        self.contextMenuConfiguration = contextMenuConfiguration
     }
 
     nonisolated static func == (left: Self, right: Self) -> Bool {

Tests/Fakes/FakeTextModel.swift

@@ -31,6 +31,10 @@ struct FakeTextCellViewModel: CellViewModel {
         self.model.text
     }
 
+    var shouldSelect = true
+
+    var shouldDeselect = true
+
     var shouldHighlight = true
 
     var contextMenuConfiguration: UIContextMenuConfiguration?
@@ -45,6 +49,11 @@ struct FakeTextCellViewModel: CellViewModel {
         self.expectationDidSelect?.fulfillAndLog()
     }
 
+    var expectationDidDeselect: XCTestExpectation?
+    func didDeselect(with coordinator: (any CellEventCoordinator)?) {
+        self.expectationDidDeselect?.fulfillAndLog()
+    }
+
     var expectationWillDisplay: XCTestExpectation?
     func willDisplay() {
         self.expectationWillDisplay?.fulfillAndLog()
@@ -67,10 +76,14 @@ struct FakeTextCellViewModel: CellViewModel {
 
     init(
         model: FakeTextModel = FakeTextModel(),
+        shouldSelect: Bool = true,
+        shouldDeselect: Bool = true,
         shouldHighlight: Bool = true,
         contextMenuConfiguration: UIContextMenuConfiguration? = nil
     ) {
         self.model = model
+        self.shouldSelect = shouldSelect
+        self.shouldDeselect = shouldDeselect
         self.shouldHighlight = shouldHighlight
         self.contextMenuConfiguration = contextMenuConfiguration
     }

Tests/TestCellEventCoordinator.swift

@@ -50,4 +50,28 @@ final class TestCellEventCoordinator: UnitTestCase, @unchecked Sendable {
 
         self.keepDriverAlive(driver)
     }
+
+    @MainActor
+    func test_didDeselectCell_getsCalled() {
+        let cell = FakeCellViewModel()
+        let section = SectionViewModel(id: "id", cells: [cell])
+        let model = CollectionViewModel(id: "id", sections: [section])
+
+        let coordinator = FakeCellEventCoordinator()
+        coordinator.expectationDidDeselect = self.expectation()
+
+        let driver = CollectionViewDriver(
+            view: self.collectionView,
+            viewModel: model,
+            options: .test(),
+            cellEventCoordinator: coordinator
+        )
+
+        let indexPath = IndexPath(item: 0, section: 0)
+        driver.collectionView(self.collectionView, didDeselectItemAt: indexPath)
+
+        self.waitForExpectations()
+
+        self.keepDriverAlive(driver)
+    }
 }