validate abstract method

Map<String, String?> validate()

Each field's error message, or null when it's valid; FormValidators fit here directly.

Example:

@override
Map<String, String?> validate() => {
  'name': FormValidators.required(name),
  'email': FormValidators.email(email),
  'age': (age ?? 0) < 18 ? 'You must be 18 or older' : null,
};

Implementation

Map<String, String?> validate();