Using Swift DispatchGroups

Swift’s DispatchGroups are useful for doing stuff after a group of asynchronous operations. In my Day Planner app, I’ve got to load items from the iOS calendars (where some of the APIs return asynchronously). Using a DispatchGroup allows me to efficiently wait for all the data to reload and then update the user interface to reflect the changes.

let dispatchGroup = DispatchGroup()

for item in self.items {

  // Signal that we're entering a new execution block

  item.loadAsync {
    // Signal that we've finished.

dispatchGroup.notify(queue: .main, execute: {
  // Do something with the data, once all of the loadAsync calls have finished.

Change Log

  • 12/4/2017 - Initial Revision

Found a typo or technical problem? file an issue!