Swift method to provide the equivalent of `@synchronised` from objc

synchronized.swift

/// Provide the equivalent of @synchronised on objc
private func synchronized<T>(_ lock: AnyObject, _ body: () throws -> T) rethrows -> T {
   objc_sync_enter(lock)
   defer { objc_sync_exit(lock) }
   return try body()
}

/// Simple lockable class
class Lockable {
   private var lockable: AnyObject
   init(using lockable: AnyObject) {
      self.lockable = lockable
   }
   func usingLock<Value>(_ body: () throws -> Value) rethrows -> Value {
      objc_sync_enter(self.lockable)
      defer { objc_sync_exit(self.lockable) }
      return try body()
   }
}

Usage :-

func remove(document: MyDocument) -> Bool {
    return synchronized(self) {
        RemoveDocument(self.index, document)
    }
}

func add(text: String) -> Void {
    synchronized(self) {
        AddDocumentWithText(self.index, text)
    }
}