Can you give an example of implementing the Singleton pattern in code?

In Dart (the language used in Flutter), the Singleton pattern can be implemented using a private constructor and a static field that holds the single instance of the class. Here's a simple example:

class Singleton {
  // Private constructor
  Singleton._privateConstructor();

  static final Singleton _instance = Singleton._privateConstructor();

  // Factory constructor returns the single instance
  factory Singleton() {
    return _instance;
  }

  void someMethod() {
    print('Calling Singleton method');
  }
}

void main() {
  var s1 = Singleton();
  var s2 = Singleton();

  print(identical(s1, s2)); // true, both objects are the same
  s1.someMethod();
}

Thus, the Singleton class guarantees that only one instance will be created, and all constructor calls return this same object.