Can you name the main design patterns in object-oriented programming?

The main design patterns in object-oriented programming, which are also often used in Flutter, include:

• Singleton — ensures that a class has only one instance and provides a global point of access to it.
• Factory Method — defines an interface for creating an object but allows subclasses to alter the type of objects that will be created.
• Builder — separates the construction of a complex object from its representation, allowing the same construction process to create different representations.
• Observer — defines a dependency between objects so that when one object changes its state, all its dependents are notified and updated automatically.
• Decorator — dynamically adds responsibilities to objects.
• Strategy — defines a family of algorithms, encapsulates each one, and makes them interchangeable.

In Flutter, patterns related to state management, such as Provider and Bloc, are often used, which are based on the principles of Observer and other patterns.

Example of Singleton in Dart:

class Singleton {
  Singleton._privateConstructor();

  static final Singleton _instance = Singleton._privateConstructor();

  factory Singleton() {
    return _instance;
  }
}