DifferenceKit use ContentEquatable protocol to produce items update. DataSource wrap items into struct which implement Differentiable protocol. In fact diff algorithm never produce update events, there is only one way - call reload method in DataSource. We would like to implement ContentEquatable for DataSource items and get ChangeSet with updates.

Checklist

• [x] All tests are passed.
• [x] Searched existing pull requests for ensure not duplicated.

Description

Swift Compiler Error because of Collection Naming issue

Motivation and Context

Release Build ERROR Swift Compiler!

Hello!

First and foremost; これを作ってくれて、ありがとうございます！助かりました 🙇🏻‍♂️

I have noticed a minor issue, which I have described below using the issue template. I've also forked this repo and applied a fix, which you can find here: https://github.com/simba909/DiffableDataSources

I would be happy to provide a pull request 👍🏻

Checklist

• [x] This is not a Apple's bug.
• [x] Reviewed the README and documents.
• [x] Searched existing issues for ensure not duplicated.

Expected Behavior

When using this library and applying two snapshots after one another, I expect the two snapshots to be correctly differentiated like in Apple's NSDiffableDataSource so that item updates are correctly reflected between the two snapshots. Below is some sample code that demonstrates the use-case:

struct MyItem: Hashable, Equatable {
    let id: Int
    var name: String

    func hash(into hasher: inout Hasher) {
        hasher.combine(id)
    }
}

let snapshot = DiffableDataSourceSnapshot<Int, MyItem>()
snapshot.appendSections([0])

let myItem = MyItem(id: 1, name: "Test")
snapshot.appendItems([myItem])

dataSource.apply(snapshot) // <-- This works great, and as expected

// Now, let's apply another snapshot that includes an update to the item
let anotherSnapshot = DiffableDataSourceSnapshot<Int, MyItem>()
anotherSnapshot.appendSections([0])

let updatedItem = MyItem(id: 1, name: "Test 2") // <-- Notice that the id is the same, but the content is different
anotherSnapshot.appendItems([myItem])

dataSource.apply(anotherSnapshot) // <-- This results in 1 deletion, 1 insertion when it should produce 1 reload

Current Behavior

Item reloads are not discovered in complex items, because an equality check is used on the SnapshotStructure.Item differenceIdentifier instead of the hash value.

Steps to Reproduce

1. Create an Xcode project using this library
2. Take the small sample pasted above and put it in the project
3. Run the project, and notice how items are deleted/inserted instead of reloaded

Thank you for creating this project, it's become really useful in few of my projects!

However I have noticed few methods from the official UITableViewDiffableDataSource are missing from your implementation:

• func tableView(UITableView, canEditRowAt: IndexPath) -> Bool
• func tableView(UITableView, canMoveRowAt: IndexPath) -> Bool
• func tableView(UITableView, cellForRowAt: IndexPath) -> UITableViewCell
• func tableView(UITableView, commit: UITableViewCell.EditingStyle, forRowAt: IndexPath)
• func tableView(UITableView, moveRowAt: IndexPath, to: IndexPath)

Reference: https://developer.apple.com/documentation/uikit/uitableviewdiffabledatasource

Naturally I'd expect these methods to be open and overridable to be able to construct and apply a new snapshot separately.

Expected Behavior

Subclassing the TableViewDiffableDataSource should allow to override and provide a custom implementation for canEditRowAt/canMoveRowAt protocol methods.

class MyDiffableDataSource: TableViewDiffableDataSource<SectionViewModel, AnyViewModel> {
    func tableView(_: UITableView, canEditRowAt indexPath: IndexPath) -> Bool {
        return true
    }

    func tableView(_: UITableView, commit editingStyle: UITableViewCell.EditingStyle, forRowAt indexPath: IndexPath) {
        // Custom implementation
    }
}

Current Behavior

Methods canEditRowAt and commit:editingStyle:forRowAt do not get executed when implemented on a subclass. This is probably because the base class does not provide an open/public default implementations for these.

Checklist

• [ ] All tests are passed.
• [ ] Added tests.
• [ ] Documented the code using Xcode markup.
• [x] Searched existing pull requests for ensure not duplicated.

Description

This library provides a back port to UITableViewDiffableDataSource, UICollectionViewDiffableDataSource, and NSCollectionViewDiffableDataSource and tries to stay as close to the API as possible.

However, one part of the API is missing for UICollectionView and UITableView that does not exist for NSCollectionView which is the Completio block of applying the difference.

UIKIt: apply(_:animatingDifferences:completion:) AppKit: applySnapshot:animatingDifferences:

However, to achieve this we would need to change the internals of DifferenceKit on the reload method to accept a completion block and call it once it is done applying the difference.

Motivation and Context

By providing a completion on apply method, the API will be exactly as Apple's APIs.

Impact on Existing Code

As Apple's API completion block is optional, the function parameter could default to nil and this will not effect the client code and will not cause any breaking changes.

Checklist

• [x] Reviewed the README and documents.
• [x] Searched existing issues for ensure not duplicated.

Expected Behavior

I'd like to show a header or footer view for a section of a table view.

Current Behavior

I'm able to use DiffableDataSources to create sections and add items to the section, and this generates cells, but I cannot figure out how to create a header or a footer view (e.g. a UITableViewHeaderFooterView) for a section of the table view.

For example , if I have:

enum Section {
  case .greetings
}

enum Row {
  case .hello
  case .goodbye
}

func buildSnapshot() {
  let snapshot = DiffableDataSourceSnapshot<Section, AnyHashable>()
  snapshot.appendSections([.greetings])
  snapshot.appendItems(Row.allCases, toSection: .greetings)
  return snapshot
}

lazy var dataSource = TableViewDiffableDataSource<Section, AnyHashable> (tableView: tableView) { tableView, indexPath, item in
  // this is only called for .hello and .goodbye
  // and i can only return a UITableViewCell - not a UITableViewHeaderFooterView
}

## Environment
- version: 0.1.0

- Swift version: 5.0.1

Checklist

• [x] Reviewed the README and documents.
• [x] Searched existing issues for ensure not duplicated.

Expected Behavior

I'd like to use DiffableDataSources with different cell types.

Current Behavior

I'm able to create a single data source and single cell type and apply the changes. I'm obviously missing something because I cannot figure out how to create a data source that vends multiple object types. (I tried creating multiple data sources, but then ended up with the dreaded UICollectionView exceptions about attempt to delete item 2 from section 0 which only contains 2 items before the update.)

Detailed Description (Include Screenshots)

Here is how I'm creating "article" cells. I'm not sure how to create another cell type.

enum Section: Int, CaseIterable {
    case trends = 0
    case articles

    var cellIdentifier: String {
        switch self {
        case .trends:
            return "trendCell"
        case .articles:
            return "articleCell"
        }
    }
}

lazy var dataSource = CollectionViewDiffableDataSource<Section, Article> (collectionView: collectionView) { collectionView, indexPath, _ /*identifier*/ in
    if let cell = collectionView.dequeueReusableCell(withReuseIdentifier: Section.articles.cellIdentifier, for: indexPath) as? ArticleCollectionViewCell {
        cell.article = self.articles[indexPath.item]
        return cell
    }

    fatalError()
}

var articles: [Article] = [] {
    didSet {

            let snapshot = DiffableDataSourceSnapshot<Section, Article>()
            snapshot.appendSections([.articles])
            snapshot.appendItems(articles, toSection: .articles)
            dataSource.apply(snapshot, animatingDifferences: true)
        }
    }
}

Environment

• version: 0.1.0

• Swift version: 5.0

• iOS version: 12.2

• Xcode version: 10.2.1

• Devices/Simulators: iPhone X

• CocoaPods/Carthage version: 0.33.0

Checklist

• [x] This is not an Apple's bug. It works on the original implementation.
• [x] Reviewed the README and documents.
• [x] Searched existing issues for ensure not duplicated.

Expected Behavior

Applying two sets of trivial data to a collectionview, I expect the UI to match it in all cases - or at least understand which exceptional cases I should guard against and work them around as needed.

Current Behavior

Filtering a simple model array to a particular state makes the collection view fail to display them correctly, whereas the apple implementation does it.

Steps to Reproduce

1. Create a snapshot from an array of Hashable models that combines the state from an array of model objects (simple id/title strings) and a isFavorite boolean value)
2. Given a state0 (full list), filter it into state1 (filtered by some criteria)
3. Filter it again into state1 (different, non-exclusive criteria)
4. Toggle applying state1 and state2 to the table view. Going from state1 -> state2 yield different changesets every time you run it, most of the time resulting in wrong state

The collection view shows more items after snapshot from state2 being applied, than the actual array/snapshot has. The indexes get mixed up between what you tap and what is in the source array

Detailed Description (Include Screenshots)

I don't understand the cause exactly.

Reproducible Demo Project

https://github.com/rafaelnobrekz/DiffableBugRepro

Environments

• version: 0.5.0 (DifferenceKit 1.2.0)

• Swift version: 5.7

• iOS version: iOS 16

• Xcode version: Xcode 14

• Devices/Simulators: iPhone 14 Pro Simulator (iOS 16), iPhone 12 Pro (iOS 16), iPhone 7 Plus (iOS13.7)

• CocoaPods/Carthage version: n/a (SPM)

Checklist

• [x] All tests are passed.
• [ ] Added tests.
• [ ] Documented the code using Xcode markup.
• [ ] Searched existing pull requests for ensure not duplicated.

Description

Similarly to ra1028/DifferenceKit#124, this makes sure the project gets built for ARM64. That requires DifferenceKit 1.2.0 so I updated the dependencies to DifferenceKit.

Related Issue

#36

Motivation and Context

Impact on Existing Code

Screenshots (if appropriate)

Checklist

• [x] All tests are passed.
• [x] Added tests.
• [x] Documented the code using Xcode markup.
• [x] Searched existing pull requests for ensure not duplicated.

Description

As per #16 , when implementing a table view delegate there are currently some methods that aren't implemented. It is currently possible to add these methods by using @objc(…) modifier, but I feel like a default, open for overriding implementation achieves a better experience after all.

Related Issue

Introduction of default implementations for other UITableViewDelegate and UICollectionViewDelegate methods - #16

Impact on Existing Code

No impact on existing code.

Checklist

• [x] Reviewed the README and documents.
• [x] Searched existing issues for ensure not duplicated.

Description

We want to have a getter function for the SectionIdentifierType, to be able to use different cell types depending on the section they are in.

Motivation and Context

We want to use IBPCollectionViewCompositionalLayout with different layouts per section. IBPCollectionViewCompositionalLayout refers to this datasource library. In the current implementation we were not able to achieve that because of the missing getter for the SectionIdentifierType.

Proposed Solution

Adding a subscript function for the SectionIdentifierType.

Bumps tzinfo from 1.2.5 to 1.2.10.

Dependabot will resolve any conflicts with this PR as long as you don't alter it yourself. You can also trigger a rebase manually by commenting @dependabot rebase.

Bumps cocoapods-downloader from 1.3.0 to 1.6.3.

Dependabot will resolve any conflicts with this PR as long as you don't alter it yourself. You can also trigger a rebase manually by commenting @dependabot rebase.

Checklist

• [x] Reviewed the README and documents.
• [x] Searched existing issues for ensure not duplicated.

Description

DiffableDataSources should support ARM Macs.

Motivation and Context

DiffableDataSources currently only gets built for x86_64 for macOS and the Simulator. Now that all new Macs use an ARM CPU, DiffableDataSources should also be built for ARM.

Proposed Solution

Checklist

• [YES] All tests are passed.
• [YES] Added tests.
• [YES] Documented the code using Xcode markup.
• [YES] Searched existing pull requests for ensure not duplicated.

Description

Added method sectionIdentifier(for section: Int) -> SectionIdentifierType for data sources.

Related Issue

https://github.com/ra1028/DiffableDataSources/issues/33

Checklist

• [YES] Reviewed the README and documents.
• [YES] Searched existing issues for ensure not duplicated.

Description

When it's called just after applying deleted section

    func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, insetForSectionAt section: Int) -> UIEdgeInsets {

        // it crashes when it's called just after applying deleted section
        let sectionIdentifier1 = self.dataSource.snapshot().sectionIdentifiers[section]

        // it would be nice to have sth like this as data source is still correct when snapshot actually isn't
        let sectionIdentifier2 = self.dataSource.sectionIdentifier(for: section) 

        // I need to know which section is here
    }

then it crashes or it's not possible to get section identifier in UICollectionViewDelegate methods.

Checklist

• [x ] This is not a Apple's bug.
• [x ] Reviewed the README and documents.
• [x ] Searched existing issues for ensure not duplicated.

Expected Behavior

trailingSwipeActionsConfigurationForRowAt is called

Current Behavior

trailingSwipeActionsConfigurationForRowAt not called

Steps to Reproduce

1. Create table view with diffable data source
2. Implement table view delegate's method tableView( tableView: UITableView, trailingSwipeActionsConfigurationForRowAt indexPath: IndexPath)_ )
3. Set data source to diffable data source and delegate to self.
4. See that it's not called

Environments

• version: 0.4.0
• Swift version: 5.2
• iOS version: 14.2
• Xcode version: 12.2
• Devices/Simulators: iPhone 7/iPhone 11 Pro
• CocoaPods/Carthage version: 0.4.0