With WWDC 2021 just around the corner I've been thinking about what I'd like to see there.
A lot of the popular discourse around this time of year is focussed on features of the operating systems but I want to look at what I'd like to see as a developer for Apple platforms.
I love to develop for Apple platforms but it can often be a painful process. May is like a christmas for Apple developers.
Partial fix for #31
Added to work around https://bugs.swift.org/browse/SR-14103
Overall this is pretty minor but when dealing with a lot of SingleElementSections that are infrequently updated is does start to slow down.
I thought a faster approach would be to use generics on replace(element:) to only check for nil when the value is Optional, but generics don't allow for this kind of overload.
Also added some basic tests. The performance tests show a ~9% performance increase.
Replacing https://github.com/composed-swift/ComposedUI/pull/15
This PR is being used to diff between the OpenNet fork.
Hopefully other PRs will be merged before this (e.g. https://github.com/composed-swift/Composed/pull/21), which should lead to this PR having no changes and purely to ensure some of the history is not lost.
We've discussed returning -1 not being great previously, but now we have the 2.0 branch we can make this change :)
@bill201207 found that UINib(nibName:bundle:) is a big part of the poor performance when our app launches.
Ultimately batching updates will help with a lot of things like this, but really that'll just be masking some of the performance issues so it's useful to find issues like this now.
When displaying an alert in SwiftUI, if the value used to calculate whether the alert is presented is both Optional and does not conform to Identifiable1 it is often recommended to use a separate flag, similar to:
struct ContentView: View { @State private var alertText: String? @State private var isPresentingAlert = false var body: some View { Button("Show Alert") { self.alertText = "Alert Text" self.isPresentingAlert = true } .alert(isPresented: $isPresentingAlert) { Alert(title: Text(alertText!)) } } }
There are 2 main downsides to this:
alertText is not set back to nil, which may cause bugs and will increase memory usage (even if only a little in this case)isPresentingAlert flag needs to be managedTo work around these issues I create a small extension to Binding the allows this same code to be updated to:
struct ContentView: View { @State private var alertText: String? var body: some View { Button("Show Alert") { self.alertText = "Alert Text" } .alert(isPresented: $alertText.mappedToBool()) { Alert(title: Text(alertText!)) } } }
The extension is fairly small and simple:
import os.log import SwiftUI extension Binding where Value == Bool { /// Creates a binding by mapping an optional value to a `Bool` that is /// `true` when the value is non-`nil` and `false` when the value is `nil`. /// /// When the value of the produced binding is set to `false` the value /// of `bindingToOptional`'s `wrappedValue` is set to `nil`. /// /// Setting the value of the produce binding to `true` does nothing and /// will log an error. /// /// - parameter bindingToOptional: A `Binding` to an optional value, used to calculate the `wrappedValue`. public init<Wrapped>(mappedTo bindingToOptional: Binding<Wrapped?>) { self.init( get: { bindingToOptional.wrappedValue != nil }, set: { newValue in if !newValue { bindingToOptional.wrappedValue = nil } else { os_log( .error, "Optional binding mapped to optional has been set to `true`, which will have no effect. Current value: %@", String(describing: bindingToOptional.wrappedValue) ) } } ) } } extension Binding { /// Returns a binding by mapping this binding's value to a `Bool` that is /// `true` when the value is non-`nil` and `false` when the value is `nil`. /// /// When the value of the produced binding is set to `false` this binding's value /// is set to `nil`. public func mappedToBool<Wrapped>() -> Binding<Bool> where Value == Wrapped? { return Binding<Bool>(mappedTo: self) } }
The extension isn't tied directly to showing an alert or a sheet and can be used in any context, but this is one of the better examples of its usage.
This extension is available on GitHub under the MIT license.
1 If it does conform to Identifiable use alert(item:content:)
This adds the ComposedLayout and ComposedUI packages, which will close #16.
The base for this is 2.0-beta, which we can use for testing new changes, which can also break API.
If you go to the repo settings you can (temporarily) set the default branch to 2.0-beta and we can add a note to the README stating this is the beta release and the stable release is available in the master branch.
Once merged and these changes are made the READMEs for ComposedLayout and ComposedUI repos can be updated to point to this repo and their repos archived.
This is a new type of section that is similar to ComposedSectionProvider, but rather than flattening each of the children in to a single SectionProvider it flattens them in to a single Section.
The ComposedUI side of this has been updated to support multiple cells per section, with a convenience for FlatSection that delegates the calls to each of the flattened sections.
This is a breaking change since the protocol requirements have changed. I have set the base of the PR to merge-all-libraries since that's also a breaking change and this PR relies on those changes.
edit: We've moved to our own fork to allow for more rapid development. The latest changes are in https://github.com/opennetltd/Composed/tree/feature/FlatSection, which will eventually be merged back in to this repo once some of the other PRs/issues have been resolved.
In my open source frameworks I usually use the last major Xcode (currently 11.7), latest (currently 12.3) and latest beta (soon to be 12.4), but this project has only been setup for the latest version of Xcode.
If we feel it's good to run the tests across multiple Xcode versions I have created https://github.com/JosephDuffy/update-xcode-version-action, which we can use to keep the versions in-sync with the versions available as part of GitHub actions.
For now I've removed all use a explicit Xcode versions.
Regression introduce in 1.1.1.
Would occur when a segmented provider was the last child of a composed provider and the selected segment changed.
This could have also been fixed in SegmentedSectionProvider but changing the _currentIndex after the delegate has been notified (which is closer to what ComposedSectionProvider does) but we have nothing in the API contract stating this must be done, so really it's an issue with the caching in ComposedSectionProvider.
These properties are accessed quite frequently and can be cached with a little extra processing.
This is another finding from screens that have a large number of composed sections.
This and https://github.com/composed-swift/ComposedUI/pull/15 seem to be the main areas of performance issues, although that doesn't mean that once these are working and merged we won't uncover more 😅
Thanks to @bill201207 for their contributions to this change.
The idea of this is that without breaking the API the collection view will batch updates.
Inserting a large number of sections is the main area of performance loss we are currently encountering, because the sections are inserted individually and not batched. This change alone has reduce the initial load time of one our screens (which has 100-150 sections added at once) from 30-45 seconds down to less than a second (at least it is not noticeable).
I had created https://github.com/composed-swift/Composed/pull/17 to try and address this, which has the advantage that it would apply to other view types (e.g. UITableView), but I believe does not offer the same performance improvements and it is restricted to a single ComposedSectionProvider.
This is a draft to collect feedback; as you can see there are some TODOs but I think there's enough implemented to provide an overview of the changes that would be required to implement this.
This does not currently work; there are situations that cause the collection NSInternalInconsistencyException', reason: 'Invalid update error. I have some failing tests that demonstrate what the result should be.
When adding a lot of sections (we have a screen which inserts 100~175 on initial load) the performance is quite poor.
Along with the improve-composed-section-provider-performance branch (which I want to fully validate before making a PR) performing these changes in batch helps a lot.
builder(for:) function to aid with building complex type (thanks to @randomeizer)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.
The Xcode 12 beta includes Swift 5.3 but drops support for iOS 8.x. This means that Swift packages that support iOS 8 will cause a warning:
The iOS deployment target 'IPHONEOS_DEPLOYMENT_TARGET' is set to 8.0, but the range of supported deployment target versions is 9.0 to 14.0.99.
It's not possible to remove this warning within a project that depends on a Swift package with a deployment target of iOS 8, but it is possible to fix this in the dependency without removing support for iOS 8 for older versions of Swift. There are multiple way this can be accomplished.
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.
This needs more tests to ensure full coverage, but also to prove that this was previously broken and is now fixed.
The added function is public because I'm using it to extract a subset of the entries in the archive that contains symlinks.
#185, possibly #62.
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.
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:
If I insert a section at index 3 should it look like:
or
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.
The package(s) being submitted are:
I have either:
swift ./validate.swift.Or, checked that:
Package.swift file in the root folder.swift package dump-package with the latest Swift toolchain.https and the .git extension.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.
A copy of Package.swift with swift-tools-version updated to 5.3 and iOS platform updated to iOS 9.
Having this as a separate file prevents breaking backwards compatibility with Swift < 5.3 projects that support iOS 8.
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:
It will do the following:
v is pushed
v0* or v*- (e.g. v1.1.0-rc1) will be marked as pre-releasegh-pages branch as part of releasesNote 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.
Improve API for Subscription/Cancellable
Add documentation
I am currently maintaining numerous Swift Packages that don't receive a constant flow of updates, but do receive updates when new Swift updates come out, or as I think of useful additions.
To ensure that I can make some of these less frequent updates without too much friction and with confidence in their correctness I rely heavily on GitHub Actions, which I'll go over in this blog post.
Much better handling of optional values, which also allows for non-optional values
Release candidate 1 for 1.0 stable release
Has lots of tests but little documentation. API has changes a lot since initial 0.1.0 but I’m happy with it now. Hopefully it is consistent and (once docs are added) easy to use.
A common pattern when using closures in Swift is to add [weak self] in the captures list to hold a weak reference to self and avoid a retain cycle. This is then often followed by the following:
guard let self = self else { return }
But I often forget that capture lists can capture other variables in the current scope, so I thought I'd highlight some other use cases.
Today I have released the 1.0.0 version of a Swift package that aids with adding Equatable and Hashable conformance by using KeyPaths.
The package is available on GitHub.
I created the Swift Playground that sparked this concept in December 2018, so this concept has been rattling around in my brain for a couple of years. The API has changed a lot since the original concept, but the core has stayed the same: a protocol that requires a single function to be implemented that uses KeyPaths to synthesise Equatable and/or Hashable conformance.
Today marks 1 year since I released a blog post demonstrating an implementation of Partial in Swift, and it also marks the release of the 1.0.0 version of a Swift package for Partial.
The package is available on GitHub and supports SwiftPM, Carthage, and CocoaPods.
This blog post will go over some of the changes that have been made since the original blog post, my rationale when making certain decisions, and how I have thought about maintenance. If you want to try out Partial and see how it can be used head over to the GitHub page.
Structs are incredibly useful in Swift, especially when representing static read-only data. However, the values of a struct often come from multiple sources, such as view controllers, network requests, and files on disk, which can make the creation of these structs cumbersome.
There are numerous methods to work around this, but each have their downsides. One of these methods is to change the struct to a class and update the properties to vars, but this removes the advantages of read-only structs. Another is to make a "builder" object, but the API of this object must be kept in-sync with the object is wraps.
Partial eliminates these problems by providing a type-safe API for building structs by utilising generics and KeyPaths. Although I learned of the concept of Partial through TypeScript – which [provides Partial as a built-in type][1] – the Swift implementation supports many more use cases.
