v2.1.1

Enhancements

• Add RealmSwift.ObjectiveCSupport.convert(object:) methods to help write
  code that interoperates between Realm Objective-C and Realm Swift APIs.
• Throw exceptions when opening a Realm with an incorrect configuration, like:
  • readOnly set with a sync configuration.
  • readOnly set with a migration block.
  • migration block set with a sync configuration.
• Greatly improve performance of write transactions which make a large number of
  changes to indexed properties, including the automatic migration when opening
  files written by Realm 1.x.

Bugfixes

• Reset sync metadata Realm in case of decryption error.
• Fix issue preventing using synchronized Realms in Xcode Playgrounds.
• Fix assertion failure when migrating a model property from object type to
  RLMLinkingObjects type.
• Fix a LogicError: Bad version number exception when using RLMResults with
  no notification blocks and explicitly called -[RLMRealm refresh] from that
  thread.
• Logged-out users are no longer returned from +[RLMSyncUser currentUser] or
  +[RLMSyncUser allUsers].
• Fix several issues which could occur when the 1001st object of a given type
  was created or added to an RLMArray/List, including crashes when rerunning
  existing queries and possibly data corruption.
• Fix a potential crash when the application exits due to a race condition in
  the destruction of global static variables.
• Fix race conditions when waiting for sync uploads or downloads to complete
  which could result in crashes or the callback being called too early.