Booleans

To represent boolean values, Dart has a type named bool. Only twoobjects have type bool: the boolean literals true and false,which are both compile-time constants.

Dart’s type safety means that you can’t use code likeif (nonbooleanValue) orassert (nonbooleanValue).Instead, explicitly check for values, like this:

  1. // Check for an empty string.
  2. var fullName = '';
  3. assert(fullName.isEmpty);
  5. // Check for zero.
  6. var hitPoints = 0;
  7. assert(hitPoints <= 0);
  9. // Check for null.
  10. var unicorn;
  11. assert(unicorn == null);
  13. // Check for NaN.
  14. var iMeantToDoThis = 0 / 0;
  15. assert(iMeantToDoThis.isNaN);