Loops

Dart gives you the same core loop constructs as most C-family languages, plus a collection-friendly for-in form you'll use constantly once you start working with lists.

The classic for loop

for (int i = 0; i < 5; i++) {
  print('Count: $i');
}

The three parts — initializer, condition, increment — run in the order you'd expect: initialize once, check the condition before every iteration, and run the increment after each pass through the body.

for-in: iterating a collection

When you're looping over the elements of something iterable (a List, Set, or Map), for-in is clearer than tracking an index manually:

final languages = ['Dart', 'Python', 'Rust'];

for (final language in languages) {
  print(language);
}

Use for-in by default when you just need each element; reach for the index-based for loop only when you actually need the index itself, or need to skip around non-sequentially.

while and do-while

int attempts = 0;

while (attempts < 3) {
  print('Attempt ${attempts + 1}');
  attempts++;
}

while checks its condition before running the body, so it can run zero times. do-while checks after, guaranteeing at least one run:

int input = -1;

do {
  print('Requesting input...');
  input = 5; // pretend this came from a user
} while (input < 0);

Choose do-while specifically when the body needs to happen at least once regardless of the condition — a common example is prompting a user and only then checking whether their answer was valid.

break and continue

for (int i = 0; i < 10; i++) {
  if (i == 3) continue; // skip this iteration, keep looping
  if (i == 6) break;    // stop the loop entirely
  print(i);
}
// prints: 0 1 2 4 5

continue skips straight to the next iteration; break exits the loop immediately, and execution resumes right after it. Both work inside any of Dart's loop types, not just for.

Iterating a Map

Maps don't hand you a single value per iteration — you typically want both the key and the value, which .entries gives you:

final prices = {'apple': 1.5, 'bread': 3.2, 'milk': 2.0};

for (final entry in prices.entries) {
  print('${entry.key}: \$${entry.value}');
}

We'll cover Map itself in detail in the collections section — for now, notice that the loop mechanics don't change at all; only what you're iterating over does.