Align between

Author: martijn00

lib/src/form_builder_validators.dart

@@ -1155,13 +1155,13 @@ class FormBuilderValidators {
   /// or equal to.
   /// - [errorText] The error message when the value is not in the range.
   /// - [checkNullOrEmpty] Whether to check for null or empty values.
-  static FormFieldValidator<num> between(
+  static FormFieldValidator<T> between<T>(
     num min,
     num max, {
     String? errorText,
     bool checkNullOrEmpty = true,
   }) =>
-      BetweenValidator(
+      BetweenValidator<T>(
         min,
         max,
         errorText: errorText,

lib/src/numeric/between_validator.dart

@@ -14,7 +14,7 @@ import '../base_validator.dart';
 /// - [checkNullOrEmpty] Whether to check if the value is null or empty.
 ///
 /// {@endtemplate}
-class BetweenValidator extends BaseValidator<num> {
+class BetweenValidator<T> extends BaseValidator<T> {
   /// Constructor for the between validator.
   const BetweenValidator(
     this.min,
@@ -37,9 +37,18 @@ class BetweenValidator extends BaseValidator<num> {
       FormBuilderLocalizations.current.betweenErrorText(min, max);
 
   @override
-  String? validateValue(num valueCandidate) {
-    final num value = valueCandidate;
-    if (value < min || value > max) {
+  String? validateValue(T valueCandidate) {
+    final num? value;
+
+    if (valueCandidate is String) {
+      value = num.tryParse(valueCandidate);
+    } else if (valueCandidate is num) {
+      value = valueCandidate;
+    } else {
+      return errorText;
+    }
+
+    if (value == null || (value < min || value > max)) {
       return errorText;
     }