Strings

string()

string() accepts a Dart String. Empty strings are valid unless you add a check.

final name = string().trim().min(2).max(80);
print(name.parse(' Ada ')); // Ada
print(name.validate('A')); // false

Length

string().min(3);     // At least 3 UTF-16 code units.
string().max(80);    // At most 80.
string().length(8);  // Exactly 8.
string().notEmpty(); // At least 1.

Length uses Dart's String.length, so some emoji count as two code units. required() remains a compatibility alias for nonempty text; use notEmpty() in new schemas. Object field presence is controlled separately.

Contents

string().pattern(RegExp(r'^[a-z0-9-]+$'));
string().contains('dart');
string().startsWith('acct_');
string().endsWith('.dart');
string().exact('active');
string().contained(['draft', 'published']);

Use contained() for string choices or enumerated() for enum names.

enum Status { draft, published }

final status = string().enumerated(Status.values);
print(status.parse('draft')); // draft, a String.

nameTransformer: changes the enum names used for matching. It does not convert the output to an enum value.

Characters and case

string().letters();
string().digits();
string().alphanumeric();
string().alphanumericWithSpaces();
string().specialCharacters();
string().allCharacters();
string().upperCase();
string().lowerCase();
string().mixedCase();

Character-family checks accept strict: false to search for a matching character instead of requiring the strict pattern. These are built-in pattern checks; use your own RegExp for an application's specific alphabet. Case checks validate text without changing it.

Formats

string().email();
string().url();
string().uri();
string().uuid();
string().cuid();
string().cuid2();
string().ulid();
string().nanoid();
string().jwt();
string().base64();
string().dateTime();
string().time();
string().hexColor();
string().card();

Format checks return strings. A date-time string does not become a DateTime; use dates for that output. JWT and card checks inspect format; they do not authenticate a token or authorize a payment.

Email addresses

final email = string().email();
print(email.validate('ada@example.com')); // true

email() checks address syntax using the package's email validator. It does not verify ownership or delivery.

Compromised passwords

string().uncompromised(lookup: ...) adds an asynchronous password-range check. Supply a PasswordRangeLookup for your range service, and call tryParseAsync() or parseAsync(). This check needs an external lookup; keep password values out of diagnostic parameters.

Transformations

print(string().trim().toLowerCase().parse(' ADA ')); // ada
string().toUpperCase();
string().encode(); // Base64 encoding.
string().decode(); // Base64 decoding.

Operations run in declaration order. Put .trim() before .min() when length should be checked after whitespace removal. Use coercion to accept supported non-string inputs, or pipes to produce another type.