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prefer-number-format

added in: 1.6.0
warning
⚙️🛠
Pro+

Warns when int, num or double values are formatted with toString instead of NumberFormat.format().

⚙️ Config​

Set ignored-invocations (default is empty) to ignore toString calls inside a specific invocation (example).

analysis_options.yaml
dart_code_metrics:
  rules:
    - prefer-number-format:
        ignored-invocations:
           - print

Example​

❌ Bad:

void main() {
  const int intValue = 5;
  const double doubleValue = 5;
  const num numValue = 5;

  final intString = intValue.toString(); // LINT: Prefer using 'NumberFormat()' to convert a number to a string value.
  final doubleString = doubleValue.toString(); // LINT: Prefer using 'NumberFormat()' to convert a number to a string value.
  final numString = numValue.toString(); // LINT: Prefer using 'NumberFormat()' to convert a number to a string value.

  final intString2 = '$intValue $5'; // LINT: Prefer using 'NumberFormat()' to convert a number to a string value.
  final doubleString2 = '$doubleValue $5.1'; // LINT: Prefer using 'NumberFormat()' to convert a number to a string value.
  final numString2 = '$numValue'; // LINT: Prefer using 'NumberFormat()' to convert a number to a string value.
}

✅ Good:

void main() {
  const int intValue = 5;
  const double doubleValue = 5;
  const num numValue = 5;

  final intString = NumberFormat().format(intValue);
  final doubleString = NumberFormat().format(doubleValue);
  final numString = NumberFormat().format(numValue);
}

Example with "ignored-invocations"​

Config
analysis_options.yaml
dart_code_metrics:
  rules:
    - prefer-number-format:
        ignored-invocations:
           - print

✅ Good:

void main() {
  const int intValue = 5;

  print(intValue); // Correct, ignored
}