If, Else, and Conditionals

Conditional logic in Dart starts exactly where you'd expect if you know any C-family language, then adds a couple of conveniences worth knowing about early.

if / else if / else

int score = 82;

if (score >= 90) {
  print('Grade: A');
} else if (score >= 80) {
  print('Grade: B');
} else if (score >= 70) {
  print('Grade: C');
} else {
  print('Grade: F');
}

Dart requires the condition to evaluate to an actual bool — unlike JavaScript, if (someString) or if (0) won't compile. This closes off a whole class of "truthy/falsy" bugs where a value like an empty string or a zero accidentally behaves like false.

String input = '';

// if (input) { ... }        // compile error: not a bool
if (input.isNotEmpty) { ... } // explicit, and correct

The ternary operator

For a simple two-way choice that produces a value, the ternary operator (condition ? ifTrue : ifFalse) is more concise than a full if/else:

int age = 20;
String category = age >= 18 ? 'adult' : 'minor';
print(category); // adult

Reach for it when both branches are short expressions. Once either branch needs more than one statement, an if/else reads more clearly than a nested ternary.

Null-aware conditionals

Combining what you saw with ?? in the previous lesson, conditionals often exist just to supply a default for a possibly-missing value — which ?? frequently replaces outright:

String? city;

// Equivalent, but the second is shorter and just as clear:
String result1 = city != null ? city : 'Unknown';
String result2 = city ?? 'Unknown';

Pattern matching with if-case

Modern Dart adds an if-case form that tests a value against a pattern and, if it matches, binds part of it to a new variable in the same step:

Object input = [1, 2, 3];

if (input case [int first, int second, ...]) {
  print('Starts with $first, $second');
} else {
  print('Did not match');
}

Here, the pattern [int first, int second, ...] checks that input is a list with at least two int elements, and if so, destructures the first two into first and second right in the condition. You won't need this often as a beginner, but recognizing it will save confusion the first time you see it in someone else's code — it's an if, just one that can also unpack its subject.

Conditionals are the backbone of almost every non-trivial program, and everything after this lesson — loops, switch statements, and eventually functions that decide what to return — builds directly on the same true/false logic you just saw.