Do you know difference between final and static keywords in Flutter?

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In Flutter, both the final and static keywords play significant roles, albeit in different contexts. Here’s a breakdown of their differences:

Final:

  • final in Flutter, as in Dart, denotes a variable or field that can be assigned a value only once.
  • When a variable is declared as final within a Flutter widget, it means that its value cannot be changed after it’s been initialized. This is particularly useful for variables representing constants or configuration values.
  • final variables are initialized at runtime, typically in the constructor or at the point of declaration, and their values remain constant throughout the widget’s lifecycle.
  • In the context of stateful widgets, final variables declared inside the State class can be used to hold values that need to persist across widget rebuilds but should not change during the widget’s lifespan.
  • Example: final String appName = 'MyApp';
class Math {
  final var pi = 3.14;
  pi = 3.1415;  // Error!
}

Static:

  • static in Flutter, as in Dart, denotes a member (variable or method) that belongs to the class rather than to instances of the class.
  • When a variable or method is declared as static within a Flutter widget or any other class, it means that it’s shared among all instances of that class and can be accessed directly without creating an instance of the class.
  • static variables are initialized once when the class is first accessed and retain their values throughout the application’s lifecycle. They are commonly used for constants, utility methods, or shared state that needs to be accessible across multiple instances of the class.
  • In Flutter, static variables or methods can be used to store application-wide state, perform utility functions, or define constants that are accessible from any part of the application.
  • Example: static const int maxItemCount = 10;
class Math {
  static var double staticPi = 3.14;
  double var pi = 3.14;
}

class ClassThatUsesMath {
  print(Math.staticPi);

  // Non-static variable must initialize class first:
  Math math = Math();
  print(math.pi);
}

In summary, while final ensures that a variable’s value remains constant after initialization within a Flutter widget or class instance, static enables the creation of variables and methods that are shared among all instances of a class, providing a mechanism for class-level consistency and accessibility across the application.