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Dart

Variables & Data Types

Declare a variable with var and Dart infers its type from the assigned value.

Example: the three declaration keywords

void main() {
  var name = 'Ada';       // type inferred, can be reassigned
  final age = 21;          // set once, never reassigned
  const pi = 3.14159;      // a true compile-time constant
  print('$name is $age years old.');
}
Ada is 21 years old.

Use final for a value that's set once and never reassigned after that (common for something computed at runtime, like a result from an API call). Use const specifically for a value known and fixed at compile time — a genuine constant, not just "I don't plan to change this." In practice, prefer final by default for anything that won't be reassigned, and reach for var only when a variable genuinely needs to change later.

Example
void main() {
  String name = 'Ada';
  int age = 21;
  print('$name is $age years old.');
}
Output
Ada is 21 years old.
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