Unsure of use of ?? in Swift

Question

I'm using this in my UITableViewController datasource to return the number of sections, as defined by my NSFetchedResultsController.

override func numberOfSectionsInTableView(tableView: UITableView) -> Int {

    return self.fetchedResultsController.sections?.count ?? 0
}

I've stumbled across this from samples on Swift and it works, but am unsure what the double ? means/does.

Help appreciated.

Answer 1

It is called the nil coalescing operator, and it is shorthand for the following:

return self.fetchedResultsController.sections != nil ? self.fetchedResultsController.sections! : 0