What design patterns do you most frequently apply in your development?

In Flutter development, I often use the following design patterns:

• Provider — for state management and dependency injection, a simple and effective way to separate logic and UI.
• Singleton — for creating a single instance of a class, for example, for working with a database or settings.
• Factory — for creating objects with different configurations, especially useful when working with widgets that can have various options.
• Builder — for step-by-step creation of complex widgets or configurations.

Example of using Singleton for a settings class:

class Settings {
  static final Settings _instance = Settings._internal();
  factory Settings() => _instance;
  Settings._internal();

  String theme = 'light';
}

void main() {
  var s1 = Settings();
  var s2 = Settings();
  print(identical(s1, s2)); // true
}