Simple Singleton pattern implementation in Dart, without using the ugly Singleton.instance or Singleton.getInstance(). Just Singleton() returns the singleton instance. Beautiful.

singleton.dart

// Singleton logic
class Singleton {
  // This makes sure Singleton() always returns the same instance
  static final Singleton _instance = Singleton._();
  Singleton._();
  factory Singleton() {
    return _instance;
  }
  
  // define any props, methods you want
  int port = 53;
}
// End Singleton logic

// some tests
void main() {
  var a = Singleton();
  print(a.port); // 53
  
  var b = Singleton();
  b.port = 007;
  print(a.port); // 007
  
  b.port = 123;
  print(a.port); // 123
  
  a.port = 433;
  print(b.port); // 433
}