When do we use late in Dart and what is its risk?

Short answer

late defers the initialization of a non-nullable variable, but reading the variable before it is assigned causes a LateInitializationError at runtime.

Explanation

Use late when you are sure the value will be set before the first read, such as a value computed inside an object's lifecycle. The keyword does not remove the need for initialization; it only moves the check from compile time to runtime, so it is not suitable for hiding an unclear initialization order.

Code example

late final String token;
void configure() {
  token = loadToken();
}

Common mistakes

• Using late just to silence the compiler without guaranteeing the initialization order.
• Forgetting that a late final cannot be assigned twice.

Follow-up questions

• How does the null safety system work in Dart?

Sources

• Dart language — Late variables