As mentioned in https://github.com/composed-swift/ComposedUI/issues/13 and https://github.com/composed-swift/ComposedUI/issues/8 there are some scenarios where the collection view’s data is out-of-sync with the data in composed.

As mentioned in https://github.com/composed-swift/ComposedUI/issues/13 calling layoutIfNeeded can trigger the data to be in sync again. In this I have added it to mappingWillBeginUpdating(_:) which appears to solve the problem.

It might be needed in replace(sectionProvider:) (because reloadData is called) and/or mappingDidInvalidate(_:) (for the same reason) but I’m still investigating.

I have validated this fix against https://github.com/composed-swift/ComposedUI/issues/8 and it fixes the crash.

https://github.com/composed-swift/ComposedUI/issues/13 still needs to be investigated and may require layoutIfNeeded to be called in mappingDidInvalidate. Marking as a draft until this is checked.

This is a major API change so is in a v2 branch. If we agree on a direction we could start adding PRs in to this branch.

This change would enable multiple changes to be applied at once, e.g. by requiring balanced calls to mappingWillBeginUpdating and mappingDidEndUpdating and only performing the updates when an equal number of mappingDidEndUpdating calls have been made. This could be a small performance improvement but would also improve animations.

By adding the performUpdate closure the changes to the model layer can be applied only when the consumer is expecting them, e.g. for UICollectionView this would be inside performBatchUpdates and would fix the existing crashes that occur when performing a change when there are pending layout changes.

Some tests and types have been commented out since this is more of a starting point for a discussion around the API than it is a solid implementation.

This is the closest I can see the API being (although it's still a breaking change) but maybe a bigger change would be better.

The biggest PITA is that the sections need to keep track of "current" data (e.g. what's being displayed by a collection view) and the "pending" data (e.g. what's about to be applied). I don't think this adds any memory overhead but it does add much more to the knowledge required when implementing a section.

These were quite hard to track down since the errors that would occur would often be visual and not a crash, although in some scenarios it did seem to trigger a crash.

I think this highlights the need for a much larger test suite.

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It also made me question the insert(_:at:) functions because it's not really clear what the index is. Should it insert it at the index in the context of the sections and providers (as it does now), or just sections?

For example, with:

• Section A
• Section Provider
  • Section B
  • Section C
• Section D
• Section E

If I insert a section at index 3 should it look like:

• Section A
• Section Provider
  • Section B
  • Section C
• New Section
• Section D
• Section E

or

• Section A
• Section Provider
  • Section B
  • Section C
• Section D
• New Section
• Section E

The tests are currently essentially empty but at a minimum this makes sure things compile on Xcode 11.7 and 12.0.

@shaps80 I think this will need updates to the repo settings to enable GitHub Actions.

Introduced in #9. #12 adds GitHub actions to ensure this doesn't occur again.

Previously there was no way to get the index of a child or even know if a Section or SectionProvider is a child of a ComposedSectionProvider.

On top of these functions new insert(_:after:) and insert(_:before:) have been added for convenience.

The completion block is called when the animation has completed, but at the end of the updates block the data has already been updated (from the perspective of the UICollectionView).

Not calling reset() and setting defersUpdate = false could cause crashes e.g. due to changes being applied multiple times.

The best way to recreate this is to have a series of updates occur very close to each other but with the "Slow Animation" setting enabled in the simulator.

This change might also apply to table views, I have not checked.

The crash would often be along the lines of "Tried to delete section at index 11 but there were only 11 sections" or would occur in elementsProvider(for:) with the error "No UI configuration available for section 11" when performing a non-data change e.g. a reload of a section

Sometimes it's useful to have multiple different cell types within a single section, for example to use sticky headers or to reduce to need for many layers of composition (which can be tricky to get animation right for).

This isn't a breaking change for consumers.

I think some of the naming should be improved if this were to be merged.

Draft because I want feedback on the impact of the feature itself rather than specifically the code.

Xcode does not support ed25519 SSH keys so if a user uses ed25519 keys to authenticate with GitHub the connection will fail. HTTPS does not require authentication (for public repos)

Config from https://developer.apple.com/documentation/avfoundation/cameras_and_media_capture/avcam_building_a_camera_app was used to make it easier to people checking out the repo to run the sample code. Only the team needs to be changed with this config.

Using embedded collection views with each one using a CollectionCoordinator would cause an infinite loop in responds(to:).

Maybe it's better to check in responds(to:)? I don't know if there are other scenarios this could happen in.

It looks like there's been a breaking API change compared to 1.0.1, albeit a small one.

ArraySection.updateDelegate was already weak and looking at the memory graph this is causing circular references

This is a copy/paste from https://github.com/JosephDuffy/Persist/, with a couple of small tweaks:

• Only tests iOS; macOS, tvOS, and watchOS were removed
• Coverage is not uploaded to Codecov; I don't have permission to add the project
• Xcode 11.5 is used; this is the latest stable version
• v2 of the cache action is used; this is the latest stable version

It will do the following:

• Perform a release when a tag starting with v is pushed
  • v0* or v*- (e.g. v1.1.0-rc1) will be marked as pre-release
• Build and upload docs to the gh-pages branch as part of releases
• Run tests against iOS when a commit is pushed

Note that the cache is not as useful as it could be right now; Swift likes to rebuild things based on inodes so the cache is largely (maybe entirely) discarded, but will be useful in a future Swift release.

You'll need to create an orphaned gh-pages branch for the docs since I don't have permissions. I don't think it needs an initial commit, although maybe you can't push an empty branch? I've never tried.

Basic Sections were not propagating updates if added via a call to invalidateAll. This is to address #2.

The issue can be recreated by using a SegmentedSectionProvider when switching to a segment that contains a Section (SectionProvider works I think)

This commit alone is likely not enough to fix this issue; updateDelegate should probably be set to nil for removed Sections, and should probably be set in more places.