PatternValidator class

A validator that checks whether a string matches a specific regular expression pattern.

The PatternValidator ensures that the input string adheres to a given regex pattern. This allows for flexible validation of various formats, such as custom identifiers, alphanumeric constraints, or other structured inputs.

Example

final validator = PatternValidator(
  r'^[A-Za-z0-9]+$',
  message: 'Only letters and numbers are allowed',
);

print(validator.validate('Valid123')); // null (valid)
print(validator.validate('Invalid@!')); // 'Only letters and numbers are allowed' (invalid)

Parameters

• pattern: The regular expression pattern used for validation.
• message: The error message returned if the validation fails.

Behavior:

• If the input value is null, validation fails.
• If the input does not match the specified regex pattern, validation fails.
• If the input matches the pattern, validation passes (null is returned).