Number static method

String? Function(String? value)? Number({ String errorMessage = 'Invalid number', String? next(String value)?, bool integerOnly = false, bool allowNegative = true, bool allowDecimal = true, })

Returns a validator that checks if a string is a valid number.

Arguments :

• errorMessage : The error message to return if the string is not a valid number.
• next : A validator to run after this validator.
• integerOnly : If set to true, the validator will only accept integers.
• allowNegative : If set to false, the validator will not accept negative numbers.
• allowDecimal : If set to false, the validator will not accept decimal numbers.

Usage :

TextFormField(
validator: Validators.Number(),
),

Implementation

static String? Function(String? value)? Number({
  String errorMessage = 'Invalid number',
  String? Function(String value)? next,
  bool integerOnly = false,
  bool allowNegative = true,
  bool allowDecimal = true,
}) {
  assert(
      !integerOnly || (integerOnly && !allowDecimal),
      'integerOnly and allowDecimal cannot both be true. '
      'If you want to allow decimal numbers, set integerOnly to false');
  return (value) {
    if (value == null || value.trim().isEmpty) {
      return null;
    }

    if (integerOnly) {
      if (int.tryParse(value) == null) {
        return errorMessage;
      }
    } else {
      if (num.tryParse(value) == null) {
        return errorMessage;
      }
    }

    if (!allowNegative && value.startsWith('-')) {
      return errorMessage;
    }

    if (!allowDecimal && value.contains('.')) {
      return errorMessage;
    }

    if (next != null) {
      return next(value);
    }

    return null;
  };
}