Skip to content

Support item expanding and collapsing #146

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Open
wants to merge 4 commits into
base: main
Choose a base branch
from
Open

Support item expanding and collapsing #146

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
4 commits
Select commit Hold shift + click to select a range
450c49a
Add children property to CellViewModel
bmarkowitz Nov 16, 2024
e145eaf
Create DiffableSectionSnapshot
bmarkowitz Nov 16, 2024
eb1868b
Split apply into 2 methods, for section & standard snapshot
bmarkowitz Nov 16, 2024
238a869
For demo purposes: Remaining pieces + example app
bmarkowitz Nov 16, 2024
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
21 changes: 17 additions & 4 deletions Example/Sources/List/ListViewController.swift
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -81,9 +81,9 @@ final class ListViewController: ExampleViewController, CellEventCoordinator {

private func makeViewModel() -> CollectionViewModel {
// Create People Section
let peopleCellViewModels = self.model.people.map {
let peopleCellViewModels = self.model.people.enumerated().map { index, person in
let menuConfig = UIContextMenuConfiguration.configFor(
itemId: $0.id,
itemId: person.id,
favoriteAction: { [unowned self] in
self.toggleFavorite(id: $0)
},
Expand All @@ -92,9 +92,12 @@ final class ListViewController: ExampleViewController, CellEventCoordinator {
}
)

let children = makeViewModel(for: person.subPeople)

return PersonCellViewModelList(
person: $0,
contextMenuConfiguration: menuConfig
person: person,
contextMenuConfiguration: menuConfig,
children: children
).eraseToAnyViewModel()
}
let peopleHeader = HeaderViewModel(title: "People", style: .small)
Expand Down Expand Up @@ -134,6 +137,16 @@ final class ListViewController: ExampleViewController, CellEventCoordinator {
// Create final view model
return CollectionViewModel(id: "list_view", sections: [peopleSection, colorSection])
}

private func makeViewModel(for people: [PersonModel]) -> [AnyCellViewModel] {
let children: [AnyCellViewModel] = people.map {
PersonCellViewModelList(person: $0,
contextMenuConfiguration: nil,
children: makeViewModel(for: $0.subPeople)).eraseToAnyViewModel()
}

return children
}
}

extension ListViewController: UIScrollViewDelegate {
Expand Down
4 changes: 3 additions & 1 deletion Example/Sources/List/PersonCellViewModelList.swift
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -23,6 +23,8 @@ struct PersonCellViewModelList: CellViewModel {

let contextMenuConfiguration: UIContextMenuConfiguration?

let children: [AnyCellViewModel]

func configure(cell: UICollectionViewListCell) {
var contentConfiguration = UIListContentConfiguration.subtitleCell()
contentConfiguration.text = self.person.name
Expand All @@ -35,7 +37,7 @@ struct PersonCellViewModelList: CellViewModel {
let flagEmoji = UICellAccessory.customView(
configuration: .init(customView: label, placement: .leading())
)
var accessories = [flagEmoji, .disclosureIndicator()]
var accessories = [flagEmoji, .disclosureIndicator(), .outlineDisclosure()]

if self.person.isFavorite {
let imageView = UIImageView(image: UIImage(systemName: "star.fill"))
Expand Down
9 changes: 8 additions & 1 deletion Example/Sources/PersonModel/PersonModel.swift
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -19,6 +19,7 @@ struct PersonModel: Hashable {
let birthdate: Date
let nationality: String
var isFavorite = false
var subPeople: [PersonModel] = []

var birthDateText: String {
self.birthdate.formatted(date: .long, time: .omitted)
Expand All @@ -45,7 +46,13 @@ extension Date {
extension PersonModel {
static func makePeople() -> [PersonModel] {
[
PersonModel(name: "Noam Chomsky", birthdate: Date(year: 1_928, month: 12, day: 7), nationality: "🇺🇸"),
PersonModel(name: "Noam Chomsky", birthdate: Date(year: 1_928, month: 12, day: 7), nationality: "🇺🇸", subPeople: [
.init(name: "Steve Jobs", birthdate: Date(year: 1955, month: 2, day: 24), nationality: "🇺🇸", subPeople: [
.init(name: "Another Steve Jobs", birthdate: Date(year: 1955, month: 2, day: 24), nationality: "🇺🇸", subPeople: [
.init(name: "Yet Another Steve Jobs", birthdate: Date(year: 1955, month: 2, day: 24), nationality: "🇺🇸")
])
])
]),
PersonModel(name: "Emma Goldman", birthdate: Date(year: 1_869, month: 6, day: 27), nationality: "🇷🇺"),
PersonModel(name: "Mikhail Bakunin", birthdate: Date(year: 1_814, month: 5, day: 30), nationality: "🇷🇺"),
PersonModel(name: "Ursula K. Le Guin", birthdate: Date(year: 1_929, month: 10, day: 21), nationality: "🇺🇸"),
Expand Down
12 changes: 12 additions & 0 deletions Sources/CellViewModel.swift
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -38,6 +38,10 @@ public protocol CellViewModel: DiffableViewModel, ViewRegistrationProvider {
/// This corresponds to the delegate method `collectionView(_:contextMenuConfigurationForItemAt:point:)`.
var contextMenuConfiguration: UIContextMenuConfiguration? { get }

/// Returns an array of children for the cell.
/// These children correspond to the items that have been appended to this item as part of a `NSDiffableDataSourceSectionSnapshot`.
var children: [AnyCellViewModel] { get }

/// Configures the provided cell for display in the collection.
/// - Parameter cell: The cell to configure.
@MainActor
Expand Down Expand Up @@ -90,6 +94,9 @@ extension CellViewModel {
/// Default implementation. Returns `true`.
public var shouldHighlight: Bool { true }

/// Default implementation. Returns `[]`.
public var children: [AnyCellViewModel] { [] }

/// Default implementation. Returns `nil`.
public var contextMenuConfiguration: UIContextMenuConfiguration? { nil }

Expand Down Expand Up @@ -198,6 +205,9 @@ public struct AnyCellViewModel: CellViewModel {
/// :nodoc:
public var shouldHighlight: Bool { self._shouldHighlight }

/// :nodoc:
public var children: [AnyCellViewModel] { self._children }

/// :nodoc:
public var contextMenuConfiguration: UIContextMenuConfiguration? { self._contextMenuConfiguration }

Expand Down Expand Up @@ -251,6 +261,7 @@ public struct AnyCellViewModel: CellViewModel {
private let _shouldDeselect: Bool
private let _shouldHighlight: Bool
private let _contextMenuConfiguration: UIContextMenuConfiguration?
private let _children: [AnyCellViewModel]
private let _configure: @Sendable @MainActor (CellType) -> Void
private let _didSelect: @Sendable @MainActor (CellEventCoordinator?) -> Void
private let _didDeselect: @Sendable @MainActor (CellEventCoordinator?) -> Void
Expand All @@ -276,6 +287,7 @@ public struct AnyCellViewModel: CellViewModel {
self._shouldSelect = viewModel.shouldSelect
self._shouldDeselect = viewModel.shouldDeselect
self._shouldHighlight = viewModel.shouldHighlight
self._children = viewModel.children
self._contextMenuConfiguration = viewModel.contextMenuConfiguration
self._configure = {
viewModel._configureGeneric(cell: $0)
Expand Down
20 changes: 10 additions & 10 deletions Sources/CollectionViewDriver.swift
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -328,45 +328,45 @@ extension CollectionViewDriver: UICollectionViewDelegate {
/// :nodoc:
public func collectionView(_ collectionView: UICollectionView,
shouldSelectItemAt indexPath: IndexPath) -> Bool {
self.viewModel.cellViewModel(at: indexPath).shouldSelect
self.viewModel.cellViewModel(at: indexPath, in: collectionView).shouldSelect
}

/// :nodoc:
public func collectionView(_ collectionView: UICollectionView,
didSelectItemAt indexPath: IndexPath) {
self.viewModel.cellViewModel(at: indexPath).didSelect(with: self._cellEventCoordinator)
self.viewModel.cellViewModel(at: indexPath, in: collectionView).didSelect(with: self._cellEventCoordinator)
}

/// :nodoc:
public func collectionView(_ collectionView: UICollectionView,
shouldDeselectItemAt indexPath: IndexPath) -> Bool {
self.viewModel.cellViewModel(at: indexPath).shouldDeselect
self.viewModel.cellViewModel(at: indexPath, in: collectionView).shouldDeselect
}

/// :nodoc:
public func collectionView(_ collectionView: UICollectionView,
didDeselectItemAt indexPath: IndexPath) {
self.viewModel.cellViewModel(at: indexPath).didDeselect(with: self._cellEventCoordinator)
self.viewModel.cellViewModel(at: indexPath, in: collectionView).didDeselect(with: self._cellEventCoordinator)
}

// MARK: Managing cell highlighting

/// :nodoc:
public func collectionView(_ collectionView: UICollectionView,
shouldHighlightItemAt indexPath: IndexPath) -> Bool {
self.viewModel.cellViewModel(at: indexPath).shouldHighlight
self.viewModel.cellViewModel(at: indexPath, in: collectionView).shouldHighlight
}

/// :nodoc:
public func collectionView(_ collectionView: UICollectionView,
didHighlightItemAt indexPath: IndexPath) {
self.viewModel.cellViewModel(at: indexPath).didHighlight()
self.viewModel.cellViewModel(at: indexPath, in: collectionView).didHighlight()
}

/// :nodoc:
public func collectionView(_ collectionView: UICollectionView,
didUnhighlightItemAt indexPath: IndexPath) {
self.viewModel.cellViewModel(at: indexPath).didUnhighlight()
self.viewModel.cellViewModel(at: indexPath, in: collectionView).didUnhighlight()
}

// MARK: Managing context menus
Expand All @@ -375,7 +375,7 @@ extension CollectionViewDriver: UICollectionViewDelegate {
public func collectionView(_ collectionView: UICollectionView,
contextMenuConfigurationForItemAt indexPath: IndexPath,
point: CGPoint) -> UIContextMenuConfiguration? {
self.viewModel.cellViewModel(at: indexPath).contextMenuConfiguration
self.viewModel.cellViewModel(at: indexPath, in: collectionView).contextMenuConfiguration
}

// MARK: Tracking the addition and removal of views
Expand All @@ -384,7 +384,7 @@ extension CollectionViewDriver: UICollectionViewDelegate {
public func collectionView(_ collectionView: UICollectionView,
willDisplay cell: UICollectionViewCell,
forItemAt indexPath: IndexPath) {
self.viewModel._safeCellViewModel(at: indexPath)?.willDisplay()
self.viewModel._safeCellViewModel(at: indexPath, in: collectionView)?.willDisplay()
}

/// :nodoc:
Expand All @@ -399,7 +399,7 @@ extension CollectionViewDriver: UICollectionViewDelegate {
public func collectionView(_ collectionView: UICollectionView,
didEndDisplaying cell: UICollectionViewCell,
forItemAt indexPath: IndexPath) {
self.viewModel._safeCellViewModel(at: indexPath)?.didEndDisplaying()
self.viewModel._safeCellViewModel(at: indexPath, in: collectionView)?.didEndDisplaying()
}

/// :nodoc:
Expand Down
45 changes: 38 additions & 7 deletions Sources/CollectionViewModel.swift
View file
Open in desktop
Copy link

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

We need to replace allCellsByIdentifier:

func allCellsByIdentifier() -> [UniqueIdentifier: AnyCellViewModel] {
        var allCellsDict = [UniqueIdentifier: AnyCellViewModel]()
        var cellsToProcess: [AnyCellViewModel] = []
        
        for section in self.sections {
            cellsToProcess.append(contentsOf: section.cells)
        }
        
        while let cell = cellsToProcess.popLast() {
            allCellsDict[cell.id] = cell
            cellsToProcess.append(contentsOf: cell.children)
        }
        
        return allCellsDict
    }

Note: maybe a place we can optimize performance? You have to call allCellsByIdentifier for both source and dest in _findItemsToReconfigure which size-wise can be >>> the # of cells you actually care about--visible items--which is probably around ~10 on mobile depending on ur design

Original file line number Diff line number Diff line change
Expand Up @@ -65,16 +65,19 @@ public struct CollectionViewModel: DiffableViewModel {

// MARK: Accessing Cells

/// Returns the cell for the specified `id`.
/// Returns the cell for the specified `id` by traversing each section and all of the children of each cell.
///
/// - Parameter id: The identifier for the cell.
/// - Returns: The cell, if it exists.
public func cellViewModel(for id: UniqueIdentifier) -> AnyCellViewModel? {
for section in self.sections {
for cell in section.cells where cell.id == id {
return cell
for cell in section.cells {
if let foundViewModel = cellViewModel(in: cell, with: id) {
return foundViewModel
}
}
}

return nil
}

Expand All @@ -84,14 +87,42 @@ public struct CollectionViewModel: DiffableViewModel {
/// - Returns: The cell at `indexPath`.
///
/// - Precondition: The specified `indexPath` must be valid.
Copy link

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Suggested change
/// - Precondition: The specified `indexPath` must be valid.
/// - Precondition: The specified `indexPath` must be valid and refer to a *visible* item.

In strengthening this invariant, I'm making an assumption that did-prefixed UICollectionViewDelegate methods are guaranteed to be called after a snapshot's visibleItems is updated. Experientially, is this a fine assumption to make?

public func cellViewModel(at indexPath: IndexPath) -> AnyCellViewModel {
public func cellViewModel(at indexPath: IndexPath, in collectionView: UICollectionView) -> AnyCellViewModel {
precondition(indexPath.section < self.count)
let section = self.sectionViewModel(at: indexPath.section)

let cells = section.cells
precondition(indexPath.item < cells.count)

return cells[indexPath.item]
guard let diffableDataSource = collectionView.dataSource as? DiffableDataSource
else {
return cells[indexPath.item]
}

let snapshot = diffableDataSource.snapshot(for: section.id)
let id = snapshot.visibleItems[indexPath.item]

guard let cellViewModel = cellViewModel(for: id)
else {
return cells[indexPath.item]
}

return cellViewModel
}
Comment on lines +97 to +111
Copy link

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Suggested change
guard let diffableDataSource = collectionView.dataSource as? DiffableDataSource
else {
return cells[indexPath.item]
}
let snapshot = diffableDataSource.snapshot(for: section.id)
let id = snapshot.visibleItems[indexPath.item]
guard let cellViewModel = cellViewModel(for: id)
else {
return cells[indexPath.item]
}
return cellViewModel
}
// If not using DiffableDataSource or the section is not hierarchical,
// section.cells[indexPath.item] is fine
guard let diffableDataSource = collectionView.dataSource as? DiffableDataSource,
cells.contains(where: { !$0.children.isEmpty })
else {
return section.cells[indexPath.item]
}
// Otherwise, section is hierarchical, so a valid indexPath isn't
// necessarily 1:1 with visible items. Validate indexPath is a *visible* item.
let snapshot = diffableDataSource.snapshot(for: section.id)
precondition(
indexPath.item < snapshot.visibleItems.count,
"Invalid visible index path: item \(indexPath.item) is out of bounds for visible items"
)
let itemId = snapshot.visibleItems[indexPath.item]
// Find the cell recursively (it might be a nested child)
guard let cellViewModel = cellViewModel(for: itemId) else {
preconditionFailure("Could not find cell view model for identifier: \(itemId)")
}
return cellViewModel
}


/// Recursively traverse the children array of each child to locate a matching cell view model
private func cellViewModel(in viewModel: AnyCellViewModel, with id: UniqueIdentifier) -> AnyCellViewModel? {
if viewModel.id == id {
return viewModel
}

for child in viewModel.children {
if let foundChildViewModel = cellViewModel(in: child, with: id) {
return foundChildViewModel
}
}

return nil
}

// MARK: Accessing Supplementary Views
Expand Down Expand Up @@ -168,12 +199,12 @@ public struct CollectionViewModel: DiffableViewModel {
return self.sectionViewModel(at: index)
}

func _safeCellViewModel(at indexPath: IndexPath) -> AnyCellViewModel? {
func _safeCellViewModel(at indexPath: IndexPath, in collectionView: UICollectionView) -> AnyCellViewModel? {
guard let section = self._safeSectionViewModel(at: indexPath.section),
indexPath.item < section.cells.count else {
return nil
}
Comment on lines 203 to 206
Copy link

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Suggested change
guard let section = self._safeSectionViewModel(at: indexPath.section),
indexPath.item < section.cells.count else {
return nil
}
guard let section = self._safeSectionViewModel(at: indexPath.section),
indexPath.item < section.cells.count
else {
return nil
}
// If not using DiffableDataSource or the section is not hierarchical,
// section.cells[indexPath.item] is fine
guard let diffableDataSource = collectionView.dataSource as? DiffableDataSource,
section.cells.contains(where: { !$0.children.isEmpty })
else {
return self.cellViewModel(at: indexPath, in: collectionView)
}
// Otherwise, section is hierarchical, so validate indexPath is a *visible* item
guard indexPath.item < diffableDataSource.snapshot(for: section.id).visibleItems.count
else {
return nil
}
return self.cellViewModel(at: indexPath, in: collectionView)

return self.cellViewModel(at: indexPath)
return self.cellViewModel(at: indexPath, in: collectionView)
}

func _safeSupplementaryViewModel(ofKind kind: String, at indexPath: IndexPath) -> AnySupplementaryViewModel? {
Expand Down
Loading