Adam DeLong describes how to create a singleton in Swift using NSNumberFormatter. The goal is a quick and efficient way to convert integers to a currency format, such as $99.00
“…initializing an NSNumberFormatter can be an expensive operation, I didn’t want the performance of the app to be affected by this, especially if I was going to be using the same NSNumberFormatter configuration throughout the app. So, I decided to use a singleton.”
Adam includes a screencast as well as text description of the steps.