#if __IPHONE_OS_VERSION_MAX_ALLOWED >= 100000 equivalent in Swift

Question

What is the Swift syntax for:

#if __IPHONE_OS_VERSION_MAX_ALLOWED >= 100000
//...
#endif

Answer 1

There's no direct analog of the #if compile-time directive for max OS version, but depending upon the broader objective, there are a few techniques you can avail yourself of:

1. There is a #if directive in Swift for language version (but not OS versions). See "Conditional Compilation Block" section of The Swift Programming Language: Language Reference: Statements. For example:

   #if swift(>=3.0)
   func foo(with array: [Any]) {
       print("Swift 3 implementation")
   }
   #else
   func foo(with array: [AnyObject]) {
       print("Swift 2 implementation")
   }
   #endif
   

2. You can perform #available runtime check for OS versions. See "Checking API Availability section of The Swift Programming Language: Control Flow. For example, UserNotifications framework is available effective iOS 10, so you'd do something like:

   private func registerForLocalNotifications() {
       if #available(iOS 10, *) {
           UNUserNotificationCenter.current().requestAuthorization(options: [.alert, .sound]) { granted, error in
               guard granted && error == nil else {
                   // display error
                   print(error?.localizedDescription ?? "Unknown error")
                   return
               }
           }
       } else {
           let types: UIUserNotificationType = [.badge, .sound, .alert]
           let settings = UIUserNotificationSettings(types: types, categories: nil)
           UIApplication.shared.registerUserNotificationSettings(settings)
       }
   }
   

3. If you have an API that is only available in certain OS versions, you can use @available directive. See "Declaration Attributes" discussion in The Swift Programming Language: Language Reference: Attributes for more information. For example:

   @available(iOS, introduced: 9.0, deprecated: 11.0)
   func someMethod() {
       // this is only supported iOS 9 and 10
   }
   

   or,

   @available(iOS 10.0, *)
   func someMethod() {
       // this is only available in iOS 10 and later
   }