Dart Continue Statement

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Syntax

// Unlabeled
continue;

// Labeled
continue labelName;

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Scope and Constraints

• Unlabeled continue: Strictly confined to the lexical scope of loop constructs (for, for-in, await for, while, do-while). Using an unlabeled continue outside of a loop results in a compile-time error.
• Labeled continue: Can be used within nested loops to target a specific enclosing loop, or within a switch statement to jump directly to a labeled case clause. It cannot be used as a general-purpose goto to reach arbitrary labels outside of these specific control flow structures.
• Function Boundaries: A continue statement cannot cross function boundaries. It is invalid to use continue inside a closure or local function (such as a callback passed to an Iterable.forEach() method) to skip an iteration of an enclosing loop.

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Execution Mechanics

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Unlabeled Continue (Loops)

• for loops: Control transfers directly to the update expression (e.g., i++), followed by the evaluation of the loop condition.
• while and do-while loops: Control transfers directly to the boolean condition expression.
• for-in and await for loops: Control transfers to the retrieval of the next element from the underlying Iterable or Stream.

for (int i = 0; i < 4; i++) {
  if (i == 2) {
    continue; // Bypasses the print statement when i equals 2
  }
  print(i); 
}
// Output: 0, 1, 3

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Labeled Continue (Loops)

outerLoop: // Label definition
for (int i = 0; i < 3; i++) {
  for (int j = 0; j < 3; j++) {
    if (i == 1 && j == 1) {
      // Terminates the inner loop and jumps to the 
      // update expression (i++) of outerLoop
      continue outerLoop; 
    }
    print('i: $i, j: $j');
  }
}

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Labeled Continue (Switch Statements)

int statusCode = 200;

switch (statusCode) {
  case 200:
    print('OK');
    continue redirectLabel; // Jumps directly to redirectLabel
  case 404:
    print('Not Found');
  redirectLabel: // Label attached to a specific case
  case 301:
    print('Redirecting');
}