A project (Xcode 8.2.1) demonstrating concurrency in iOS using Grand Central Dispatch (GCD) with Swift 3.
Xcode 8.2.1 project settings
To get this project running on the Simulator or a physical device (iPhone, iPad), go to the following locations in Xcode and make the suggested changes:
Project Navigator -> [Project Name] -> Targets List -> TARGETS -> [Target Name] -> General -> Signing
[ ] Tick the “Automatically manage signing” box
[ ] Select a valid name from the “Team” dropdown
Project Navigator -> [Project Name] -> Targets List -> TARGETS -> [Target Name] -> General -> Identity
[ ] Change the “com.yourDomainNameHere” portion of the value in the “Bundle Identifier” text field to your real reverse domain name (i.e., “com.yourRealDomainName.Project-Name”).