The minimum supported version of Xcode is now 15.3.

Enhancements

• Build in Swift 6 language mode when using Xcode 16. Libraries build in Swift 6 mode can be consumed by apps built in Swift 5 mode, so this should not have any immediate effects beyond eliminating some warnings and ensuring that all Realm APIs can be used in Swift 6 mode. Some notes about using Realm Swift in Swift 6:
  • try await Realm(actor: actor) has been replaced with try await Realm.open() to work around isolated parameters not being implemented for initializers (swiftlang/swift#71174). The actor is now automatically inferred and should not be manually passed in.
  • @ThreadSafe is not usable as a property wrapper on local variables and function arguments in Swift 6 mode. Sendability checking for property wrappers never got implemented due to them being quietly deprecated in favor of macros. It can still be used as a property wrapper for class properties and as a manual wrapper locally, but note that it does not combine well with actor-isolated Realms.
• Some SwiftUI components are now explicitly marked as @MainActor. These types were implicitly @MainActor in Swift 5, but became nonisolated when using Xcode 16 in Swift 5 mode due to the removal of implicit isolation when using property wrappers on member variables. This resulted in some new sendability warnings in Xcode 16 (or errors in Swift 6 mode).
• Add Xcode 16 and 16.1 binaries to the release packages (currently built with beta 6 and beta 1 respectively).

Breaking Changes

• All Atlas App Services and Atlas Device Sync functionality has been removed. Users of Atlas Device Sync should pin to v10.

• Queries on AnyRealmValue properties previously considered strings to be equivalent to Data containing the UTF-8 encoded string. Strings and Data are now considered different types and queries for one of them will not match the other.

• Realms are no longer autoreleased when initialized. This means that code along the lines of the following will no longer work:

  try! Realm().beginWrite()
  try! Realm().create(MyObject.self, value: ...)
  try! Realm().commitWrite()

  This was a pattern which was somewhat natural with the original version of the objective-c API, but only worked in debug builds and would fail in release builds. We decided to make it consistently work by forcing the Realm to be autoreleased rather than let users write code which appeared to work but was actually broken. In modern Swift this code is very strange, and autoreleasing the Realm made it much more difficult to ensure that the file is actually closed at predictable times.

  Realms are now returned retained in both debug and release modes, so this will always break rather than appearing to work. Note that there is still a weak cache of Realms and Realm() will still return a reference to the existing Realm if there is one open on the current thread.

• Iterating a Map now produces the tuple (key: KeyType, value: ValueType) rather than a very similar struct, and .asKeyValueSequence() has been removed. This aligns Map with Dictionary and makes many operations defined by Sequence work on Map.

• Passing an empty array for notification keypaths to filter on (e.g. obj.observe(keyPaths: [])) was treated the same as passing nil, i.e. no filtering was done. It now instead observes no keypaths. For objects this means it will only report the object being deleted, and for collections it will only report collection-level changes and not changes to the objects inside the collection.

• Decimal128(string:) was marked as throws, but it never actually threw an error and instead returned NaN if the string could not be parsed as a decimal128. That behavior was kept and it is no longer marked as throws.

Compatibility

• Realm Studio: 15.0.0 or later.
• Carthage release for Swift is built with Xcode 15.4.0.
• CocoaPods: 1.10 or later.
• Xcode: 15.3.0-16.1 beta.

Internal

• Upgraded realm-core from v14.12.1 to v20.0.0.

Enhancements

• Add the file path to the exception thrown by File::rw_lock() when it fails to
  open the file. (Core #7999)

Fixed

• Filtering notifications with a LinkingObjects property as the final element
  could sometimes give wrong results
  (Core #7530, since v10.11.0)
• Fix a potential crash during process termination when Logger log level is set
  higher than Info. (Core #7969, since v10.45.0)
• The check for maximum path length was incorrect and lengths between 240 and
  250 would fail to use the hashed fallback (Core #8007, since v10.0.0).
• API misuse resulting in an exception being thrown from within a callback
  would sometimes terminate due to hitting REALM_UNREACHABLE() rather than
  the exception being propagated to the caller
  (Core #7836).

Compatibility

• Realm Studio: 15.0.0 or later.
• APIs are backwards compatible with all previous releases in the 10.x.y series.
• Carthage release for Swift is built with Xcode 15.4.0.
• CocoaPods: 1.10 or later.
• Xcode: 15.1.0-16 beta 5.

Internal

• Upgraded realm-core from v14.12.0 to 14.12.1

Enhancements

• Code sign our published xcframeworks. By Apple's requirements, we should sign our release
  binaries so Xcode can validate it was signed by the same developer on every new version.
  (Apple).
• Report sync warnings from the server such as sync being disabled server-side to the sync error handler.
  (#8020).
• Add support for string comparison queries, which allows building string
  queries with the following operators (>, >=, <, <=).
  This is a case sensitive lexicographical comparison.
  (#8008).

Fixed

• -[RLMAsymmetricObject createObject:withValue:] was marked as having a
  non-null return value despite always returning nil (since v10.29.0).
• Eliminate several clang static analyzer warnings which did not report actual
  bugs.
• The async and Future versions of User.functions only worked for functions
  which took exactly one argument, which had to be an array (#8669, since 10.16.0).

Compatibility

• Realm Studio: 15.0.0 or later.
• APIs are backwards compatible with all previous releases in the 10.x.y series.
• Carthage release for Swift is built with Xcode 15.4.0.
• CocoaPods: 1.10 or later.
• Xcode: 15.1.0-16 beta 5.

Enhancements

• Improve performance of bulk object creation when the objects have embedded objects. This is particularly significant for applying sync bootstraps. (Core #7945)
• Client reset cycle detection now checks if the previous recovery attempt was made by the same version of Realm, and if not attempts recovery again (Core #7944).

Fixed

• App change notifications were being sent too soon when a new user was logged in, resulting in the user's profile being empty if it was read from within the change notification (since v10.51.0).
• A conflict resolution bug related to ArrayErase and Clear instructions could sometimes cause an "Invalid prior_size" exception when synchronizing (Core #7893, since v10.51.0).
• Sync merges which resulted in a changeset's reciprotal transformation being empty were handled incorrectly, possibly resulting in data divergence. No instances of this actually happening have been reported. (Core #7955, since v10.51.0)
• Realm.writeCopy() would sometimes incorrectly throw an exception claiming that there were unuploaded local changes when the source Realm is a synchronized Realm (Core #7966, since v10.7.6).

Compatibility

• Realm Studio: 15.0.0 or later.
• APIs are backwards compatible with all previous releases in the 10.x.y series.
• Carthage release for Swift is built with Xcode 15.4.0.
• CocoaPods: 1.10 or later.
• Xcode: 15.1.0-16 beta 5.

Internal

• Upgraded realm-core from v14.11.1 to 14.12.0

Enhancements

• Server-side role and permissions changes no longer require a client reset to
  update the local Realm. (Core #7440)

Fixed

• Deleting an object with a List<AnyRealmValue proeprty which linked to an
  object which had been deleted by another sync client would switch to the
  incorrect cascade mode and perform a cascading delete. This meant that if any
  subsequent properties in the object linked to another top-level object and
  that was the only link to that object, the target object would also be
  recursively deleted as if it was an embedded object.
  (Core #7828, since v10.51.0).
• Fix the assertion failure array_backlink.cpp:112: Assertion failed: int64_t(value >> 1) == key.value when removing links to an object (either by
  reassigning the link or by deleting the object). This could happen if the link
  came from a collection inside a AnyRealmValue, any Map, or a
  List<AnyRealmValue>, and there were more than 256 objects of the type which
  contained the link.
  (Core #7594, since v10.8.0)
• Fix the assertion failure array.cpp:319: Array::move() Assertion failed: begin <= end [2, 1] when deleting objects containing collections nested
  inside a AnyRealmValue when this caused bptree leaves to be merged.
  ()Core #7839, since v10.51.0).
• SyncSession.wait(for .upload) was inconsistent in how it handled commits
  which do no produce any changesets to upload (such as modifying flexible sync
  subscriptions). Previously if all unuploaded commits had empty changesets and
  the session had never completed a download it would wait for download
  completion, and otherwise it would complete immediate. It now always
  completes immediately. (Core #7796).
• The sync client could hit an assertion failure if a session is resumed while
  the session is being suspended. (Core #7860, since v10.27.0)
• If a sync session was interrupted by a disconnect or restart while downloading
  a bootstrap (a set of downloads caused by adding or changing a query
  subscription), stale data from the previous bootstrap could be included when
  the session reconnected and completed downloading the bootstrap. This could
  lead to objects stored in the database that do not match the actual state of
  the server and potentially leading to compensating writes.
  (Core #7827, since v10.27.0)
• Fixed unnecessary server roundtrips when there was no download to acknowledge
  (Core #2129, since v10.51.0).

Compatibility

• Realm Studio: 15.0.0 or later.
• APIs are backwards compatible with all previous releases in the 10.x.y series.
• Carthage release for Swift is built with Xcode 15.4.0.
• CocoaPods: 1.10 or later.
• Xcode: 15.1.0-16 beta 3.

Internal

• Upgraded realm-core from v14.10.2 to 14.11.0

Fixed

• Realm compaction (triggered by setting shouldCompactOnLaunch) on an
  encrypted Realm file could produce an invalid file unless the encryption key
  happened to be a valid nul-terminated string.
  (Core #7842, since v10.52.0.
• Assigning a List or Dictionary to an AnyRealmValue property which already
  stored that type of collection would only emit a clear instruction if the
  collection was not already empty. This meant that assigning to the property
  on two different clients would merge the collections if the property
  initially stored an empty collection, but would pick one of the two
  assignments to win if it was initially non-empty. If merging is the desired
  behavior, appending to the List rather than assigning a new List will still
  achieve that (Core #7809, since v10.51.0).

Compatibility

• Realm Studio: 15.0.0 or later.
• APIs are backwards compatible with all previous releases in the 10.x.y series.
• Carthage release for Swift is built with Xcode 15.4.0.
• CocoaPods: 1.10 or later.
• Xcode: 15.1.0-15.4.0.

Internal

• Upgraded realm-core from v14.10.1 to 14.10.2

Enhancements

• Add @ObservedSectionedResults.remove(atOffsets:section:) which adds the ability to
  remove a Realm Object when using onDelete on ForEach in a SwiftUI List.
• Add support for Xcode 16 beta 1 and fix some of the new warnings. Note that
  this does not yet include full support for Swift 6 language mode
  (#8618).
• Realm.asyncWrite() and Realm.asyncRefresh() now use the new #isolation
  feature to avoid sendability warnings when building with Xcode 16
  (#8618).
• Include the originating client reset error message in errors reporting that
  automatic client reset handling failed. (Core #7761)
• Improve the performance of insertion-heavy write transactions, particularly
  when setting a large number of properties on each object created
  (Core #7734).
• App now trims trailing slashes from the base url rather than producing
  confusing 404 errors. (Core #7791).

Fixed

• Deleting a Realm Object used in a @ObservedSectionedResults collection in SwiftUI
  would cause a crash during the diff on the View. (#8294, since v10.29.0)
• Fix some client resets (such as migrating to flexible sync) potentially
  failing if a new client reset condition (such as rolling back a flexible sync
  migration) occurred before the first one completed.
  (Core #7542, since v10.40.0)
• The encryption code no longer behaves differently depending on the system
  page size, which should entirely eliminate a recurring source of bugs related
  to copying encrypted Realm files between platforms with different page sizes.
  One known outstanding bug was (RNET-1141),
  where opening files on a system with a larger page size than the writing
  system would attempt to read sections of the file which had never been
  written to (Core #7698).
• There were several complicated scenarios which could result in stale reads
  from encrypted files in multiprocess scenarios. These were very difficult to
  hit and would typically lead to a crash, either due to an assertion failure
  or DecryptionFailure being thrown (Core #7698, since v10.38.0).
• Encrypted files have some benign data races where we can memcpy a block of
  memory while another thread is writing to a limited range of it. It is
  logically impossible to ever read from that range when this happens, but
  Thread Sanitizer quite reasonably complains about this. We now perform a
  slower operations when running with TSan which avoids this benign race
  (Core #7698).
• Realm.asyncOpen() on a flexible sync Realm would sometimes fail to wait for
  pending subscriptions to complete, resulting in it not actually waiting for
  all data to be downloaded. (Core #7720,
  since flexible sync was introduced).
• List<AnyRealmValue>.clear() would hit an assertion failure when used on a
  file originally created by a version of Realm older than v10.49.0.
  (Core #7771, since 10.49.0)

Compatibility

• Realm Studio: 15.0.0 or later.
• APIs are backwards compatible with all previous releases in the 10.x.y series.
• Carthage release for Swift is built with Xcode 15.4.0.
• CocoaPods: 1.10 or later.
• Xcode: 15.1.0-16 beta

Internal

• Upgraded realm-core from v14.9.0 to 14.10.1

Enhancements

• Added support for storing nested collections (List and Map not ManagedSet) in a AnyRealmValue.

  class MixedObject: Object {
    @Persisted var anyValue: AnyRealmValue
  }
  
  // You can build a AnyRealmValue from a Swift's Dictionary.
  let dictionary: Dictionary<String, AnyRealmValue> = ["key1": .string("hello"), "key2": .bool(false)]
  
  // You can build a AnyRealmValue from a Swift's Map
  // and nest a collection within another collection.
  let list: Array<AnyRealmValue> = [.int(12), .double(14.17), AnyRealmValue.fromDictionary(dictionary)]
  
  let realm = realmWithTestPath()
  try realm.write {
    let obj = MixedObject()
    obj.anyValue = AnyRealmValue.fromArray(list)
    realm.add(obj)
  }

• Added new operators to Swift's Query API for supporting querying nested collections.

  realm.objects(MixedObject.self).where { $0.anyValue[0][0][1] == .double(76.54) }

  The .any operator allows looking up in all keys or indexes.

  realm.objects(MixedObject.self).where { $0.anyValue["key"].any == .bool(false) }

• Report the originating error that caused a client reset to occur.
  (Core #6154)

Fixed

• Accessing App.currentUser from within a notification produced by App.switchToUser()
  (which includes notifications for a newly logged in user) would deadlock.
  (Core #7670, since v10.50.0).
• Inserting the same link to the same key in a dictionary more than once would incorrectly create
  multiple backlinks to the object. This did not appear to cause any crashes later, but would
  have affecting explicit backlink count queries and possibly notifications.
  (Core #7676, since v10.49.2).
• A non-streaming progress notifier would not immediately call its callback after registration.
  Instead you would have to wait for a download message to be received to get your first
  update - if you were already caught up when you registered the notifier you could end up waiting a
  long time for the server to deliver a download that would call/expire your notifier
  (Core #7627, since v10.50.0).
• After compacting, a file upgrade would be triggered. This could cause loss of data
  if deleteRealmIfMigrationNeeded is set to true.
  (Core #7747, since v10.49.0).

Compatibility

• Realm Studio: 15.0.0 or later.
• APIs are backwards compatible with all previous releases in the 10.x.y series.
• Carthage release for Swift is built with Xcode 15.4.0.
• CocoaPods: 1.10 or later.
• Xcode: 15.1.0-15.4.0.

Internal

• Upgraded realm-core from v14.6.2 to 14.9.0

Enhancements

• Update release packaging for Xcode 15.4.

Fixed

• @AutoOpen and @AsyncOpen failed to use the initialSubscriptions set in
  the configuration passed to them (PR #8572, since v10.50.0).
• App.baseURL was always nil (PR #8573, since it was introduced in v10.50.0).

Compatibility

• Realm Studio: 15.0.0 or later.
• APIs are backwards compatible with all previous releases in the 10.x.y series.
• Carthage release for Swift is built with Xcode 15.4.0.
• CocoaPods: 1.10 or later.
• Xcode: 15.1.0-15.4.0.

Drop support for Xcode 14, as it can no longer be used to submit app to the app
store. Xcode 15.1 is now the minimum supported version.

Known Issues

• Accessing App.currentUser within an App.subscribe callback would lead to a deadlock.

Enhancements

• Added SyncConfiguration.initialSubscriptions which describes the initial
  subscription configuration that was passed when constructing the
  SyncConfiguration. (#8548)
• When connecting to multiple server apps, a unique encryption key is used for
  each of the metadata Realms rather than sharing one between them
  (Core #7552).
• Improve perfomance of IN queries and chained OR equality queries for
  UUID/ObjectId types. (.Net #3566)
• Added support for updating Atlas Device Sync's base url, in case the need to roam between
  servers (cloud and/or edge server). This API is private and can only be imported using
  @_spi(Private)

  @_spi(RealmSwiftExperimental) import RealmSwift
  
  try await app.updateBaseUrl(to: "https://services.cloud.mongodb.com")

  (#8486).
• Enable building RealmSwift as a dynamic framework when installing via SPM, which
  lets us supply a privacy manifest. When RealmSwift is built as a static
  library you must supply your own manifest, as Xcode does not build static
  libraries in a way compatible with xcprivacy embedding. Due to some bugs in
  Xcode, this may require manual changes to your project:
  • Targets must now depend on only Realm or RealmSwift. If you use both the
    obj-c and swift API, depending on RealmSwift will let you import Realm.
    Trying to directly depend on both will give the error "Swift package
    target 'Realm' is linked as a static library by 'App' and 'Realm', but
    cannot be built dynamically because there is a package product with the
    same name."
  • To actually build RealmSwift as a dynamic framework, change "Do Not Embed"
    to "Embed & Sign" in the "Frameworks, Libraries, and Embedded Content"
    section on the General tab of your target's settings.
    (#8561).
• The transferredBytes and transferrableBytes fields on Progress have been deprecated
  in favor of progressEstimate which is a value between 0.0 and 1.0 indicating the estimated
  progress toward the upload/download transfer. (#8476)

Fixed

• -[RLMUser allSessions] did not include sessions which were currently
  waiting for an access token despite including sessions in other non-active
  states. (Core #7300, since v10.0.0).
• [RLMApp allUsers] included users which were logged out during the current
  run of the app, but not users which had previously been logged out. It now
  always includes all logged out users. (Core #7300, since v10.0.0).
• Deleting the active user (via User.delete()) left the active user
  unset rather than selecting another logged-in user as the active user like
  logging out and removing users does. (Core #7300, since v10.23.0).
• Fixed several issues around copying an encrypted Realm between platforms with
  different page sizes (such as between x86_64 and arm64 Apple platforms):
  • Fixed Assertion failed: new_size % (1ULL << m_page_shift) == 0 when
    opening an encrypted Realm less than 64Mb that was generated on a platform
    with a different page size than the current platform.
    (Core #7322, since v10.42.0)
  • Fixed a DecryptionFailed exception thrown when opening a small (<4k of
    data) Realm generated on a device with a page size of 4k if it was bundled
    and opened on a device with a larger page size (since the beginning).
  • Fixed an issue during a subsequent open of an encrypted Realm for some rare
    allocation patterns when the top ref was within ~50 bytes of the end of a
    page. This could manifest as a DecryptionFailed exception or as an
    assertion: encrypted_file_mapping.hpp:183: Assertion failed: local_ndx < m_page_state.size(). (Core #7319)
• Schema initialization could hit an assertion failure if the sync client
  applied a downloaded changeset while the Realm file was in the process of
  being opened (#7041, since v10.15.0).
• The reported download progress for flexible sync Realms was incorrect. It is now replaced by a
  progress estimate, which is derived by the server based on historical data and other heuristics.
  (#8476)

Compatibility

• Realm Studio: 15.0.0 or later.
• APIs are backwards compatible with all previous releases in the 10.x.y series.
• Carthage release for Swift is built with Xcode 15.3.0.
• CocoaPods: 1.10 or later.
• Xcode: 15.1.0-15.3.0.

Internal

• Upgraded realm-core from v14.5.2 to 14.6.2