Add phone validator

Author: martijn00

lib/l10n/intl_en.arb

@@ -17,5 +17,6 @@
   "notEqualErrorText": "This field value must not be equal to {value}.",
   "numericErrorText": "Value must be numeric.",
   "requiredErrorText": "This field cannot be empty.",
-  "urlErrorText": "This field requires a valid URL address."
+  "urlErrorText": "This field requires a valid URL address.",
+  "phoneErrorText": "This field requires a valid phone number."
 }

lib/src/form_builder_validators.dart

@@ -314,4 +314,13 @@ class FormBuilderValidators {
               !isDate(valueCandidate!)
           ? errorText ?? FormBuilderLocalizations.current.dateStringErrorText
           : null;
+
+  /// [FormFieldValidator] that requires the field's value to be a valid phone number.
+  static FormFieldValidator<String> phoneNumber({
+    String? errorText,
+  }) =>
+      (valueCandidate) => true == valueCandidate?.isNotEmpty &&
+              !isPhoneNumber(valueCandidate!)
+          ? errorText ?? FormBuilderLocalizations.current.phoneErrorText
+          : null;
 }

lib/src/utils/validators.dart

@@ -12,6 +12,8 @@ RegExp _creditCard = RegExp(
   r'^(?:4[0-9]{12}(?:[0-9]{3})?|5[1-5][0-9]{14}|6(?:011|5[0-9][0-9])[0-9]{12}|3[47][0-9]{13}|3(?:0[0-5]|[68][0-9])[0-9]{11}|(?:2131|1800|35\d{3})\d{11})$',
 );
 
+RegExp _phoneNumber = RegExp(r'^(\+?\d{0,1})?\(?\d{3}\)?[-.\s]\d{3}[-.\s]\d{4}$'); 
+
 int _maxUrlLength = 2083;
 
 /// check if the string [str] is an email
@@ -234,3 +236,8 @@ bool isDate(String str) {
     return false;
   }
 }
+
+/// check if the string is a valid phone number
+bool isPhoneNumber(String str) {
+  return _phoneNumber.hasMatch(str);
+}