Dart Null Safety Explained Simply

Null safety is one of Dart’s most powerful features, helping developers avoid common runtime errors caused by null references. Introduced in Dart 2.12, it ensures variables can’t contain null unless explicitly allowed. This means safer and more stable code, especially for large projects.

What Is Null Safety in Dart?

Null safety is a type system feature that separates nullable and non-nullable types. In simple terms:

• String name = "Alex"; → Non-nullable
• String? name; → Nullable

If you try to use a variable without initializing it or assign null to a non-nullable type, Dart will throw a compile-time error.

Why Is Null Safety Important?

With null safety, the Dart compiler can catch bugs before the code runs. This improves app reliability and reduces crashes, especially in production environments. It also helps tools like Flutter analyze code better for performance optimization.

Example of Null Safety in Dart

void main() {
  String? username;
  print(username?.length); // Safe access, no error even if null

  String user = "John";
  print(user.length); // Valid, not nullable
}

Migrating to Null Safety

To migrate an old Dart project to null safety, run:

dart migrate

Follow the migration tool’s recommendations and review all changes before applying.

Learn More

For deeper insight, the official Dart documentation offers a comprehensive guide on null safety.