Dart v2.9 added the late modifier on variables.

When Null Safety is enabled, it is sometimes necessary to explicitly state that we will initialize a non-null variable later. Dart cannot always assume that a variable will be initialized later, as in the case of high-level variables. The following example would throw an error in Dart.

This can be used in the following two cases.

• Late assign: promise to assign later

• Late lazy: Initializing a variable will be later.

Late assign

Promise of late assignment for the migration of your project to Null Safey

Sometimes it is necessary to explicitly state that we will initialize a non-null variable later. Dart cannot always assume that a variable will be initialized later, as in the case of high-level variables.

The following example, if the variable is not initialized before using it would throw an error in the project with Null Safey in Dart:

class Team {
  String name;
}

void main(List<String> args) {
  Team team: Team();
  team.name: 'Flutter';
  print(team.name);
}

Uncaught Error: LateInitializationError: Field 'name' has not been initialized.

In this case, we are sure that we will initialize the variable, so we can tell Dart with the reservation keyword late.

Continue this article on my personal blog here.