Singleton Pattern in Flutter

The Singleton pattern, one of the well-known “Gang of Four” design patterns, is a crucial concept for any Flutter developer. This creational design pattern ensures that a class has only one instance while providing global access to that instance.

What Makes a Singleton?

At its core, the Singleton pattern is all about controlling the creation of a single instance of a class. The key elements are:

1. Single Instance: Only one instance of the class exists.
2. Global Access: Easy access to this instance globally.
3. Controlled Instantiation: The constructor is made private to prevent direct instantiation.
4. Thread Safety: Any critical section of code must be accessed serially.

Implementing Singleton in Dart

Let’s dive into the implementation of the singleton pattern in DART using the classical approach.

class Singleton {
  static Singleton? _instance;

  // Private constructor
  Singleton._internal() {
    print('Creating an instance of the Singleton');
  }

  // Lazy instantiation
  static Singleton get instance {
    _instance ??= Singleton._internal();
    return _instance!;
  }
}

void main(){
  Singleton.instance;
  Singleton.instance;
}