Example done

README.md

@@ -145,6 +145,7 @@ new Validator({
     'age': 'You must be an adult to see this page.'
 });
 ```
+The string `{{value}}` will be replaced inside your error message automatically.
 
 # autoParse
 Oftentimes, fields that we want to validate as numbers are passed as strings.

lib/src/validator.dart

@@ -1,12 +1,15 @@
 import 'package:matcher/matcher.dart';
 
 final RegExp _asterisk = new RegExp(r'\*$');
-final RegExp _forbidden = new RegExp(r'\!$');
+final RegExp _forbidden = new RegExp(r'!$');
 final RegExp _optional = new RegExp(r'\?$');
 
 /// Returns a value based the result of a computation.
 typedef DefaultValueFunction();
 
+/// Generates an error message based on the given input.
+typedef String CustomErrorMessageFunction(item);
+
 /// Determines if a value is valid.
 typedef bool Filter(value);
 
@@ -33,7 +36,7 @@ Map<String, dynamic> autoParse(Map inputData, List<String> fields) {
 /// Enforces the validity of input data, according to [Matcher]s.
 class Validator extends Matcher {
   /// Pre-defined error messages for certain fields.
-  final Map<String, String> customErrorMessages = {};
+  final Map<String, dynamic> customErrorMessages = {};
 
   /// Values that will be filled for fields if they are not present.
   final Map<String, dynamic> defaultValues = {};
@@ -105,7 +108,7 @@ class Validator extends Matcher {
         if (!customErrorMessages.containsKey(field))
           errors.add("'$field' is forbidden.");
         else
-          errors.add(customErrorMessages[field]);
+          errors.add(customError(field, input[field]));
       }
     }
 
@@ -114,7 +117,7 @@ class Validator extends Matcher {
         if (!customErrorMessages.containsKey(field))
           errors.add("'$field' is required.");
         else
-          errors.add(customErrorMessages[field]);
+          errors.add(customError(field, 'none'));
       }
     }
 
@@ -122,7 +125,7 @@ class Validator extends Matcher {
       if (key is String && rules.containsKey(key)) {
         var valid = true;
         var value = input[key];
-        var description = new StringDescription("Field '$key': expected ");
+        var description = new StringDescription("'$key': expected ");
 
         for (Matcher matcher in rules[key]) {
           try {
@@ -132,24 +135,27 @@ class Validator extends Matcher {
               if (result.errors.isNotEmpty) {
                 errors.addAll(result.errors);
                 valid = false;
+                break;
               }
             } else {
               if (!matcher.matches(value, {})) {
                 if (!customErrorMessages.containsKey(key))
                   errors.add(matcher.describe(description).toString().trim());
                 valid = false;
+                break;
               }
             }
           } catch (e) {
             errors.add(e.toString());
             valid = false;
+            break;
           }
         }
 
         if (valid) {
           data[key] = value;
         } else if (customErrorMessages.containsKey(key)) {
-          errors.add(customErrorMessages[key]);
+          errors.add(customError(key, input[key]));
         }
       }
     }
@@ -165,6 +171,22 @@ class Validator extends Matcher {
   ValidationResult checkParsed(Map inputData, List<String> fields) =>
       check(autoParse(inputData, fields));
 
+  /// Renders the given custom error.
+  String customError(String key, value) {
+    if (!customErrorMessages.containsKey(key))
+      throw new ArgumentError("No custom error message registered for '$key'.");
+
+    var msg = customErrorMessages[key];
+
+    if (msg is String)
+      return msg.replaceAll('{{value}}', value);
+    else if (msg is CustomErrorMessageFunction) {
+      return msg(value);
+    }
+
+    throw new ArgumentError("Invalid custom error message '$key': $msg");
+  }
+
   /// Validates input data, and throws an error if it is invalid.
   ///
   /// Otherwise, the filtered data is returned.
@@ -188,7 +210,7 @@ class Validator extends Matcher {
   /// Creates a copy with additional validation rules.
   Validator extend(Map<String, dynamic> schema,
       {Map<String, dynamic> defaultValues: const {},
-      Map<String, String> customErrorMessages: const {},
+      Map<String, dynamic> customErrorMessages: const {},
       bool overwrite: false}) {
     Map<String, dynamic> _schema = {};
     var child = new Validator.empty()

pubspec.yaml

@@ -1,6 +1,6 @@
 name: angel_validate
 description: Cross-platform validation library based on `matcher`.
-version: 0.0.1
+version: 0.0.2
 author: Tobe O <thosakwe@gmail.com>
 homepage: https://github.com/angel-dart/validate
 environment:
@@ -11,4 +11,5 @@ dependencies:
 dev_dependencies:
   angel_diagnostics: ^1.0.0-dev
   angel_test: ^1.0.0-dev
+  browser: ^0.10.0
   test: ^0.12.18

web/index.html

@@ -0,0 +1,37 @@
+<!DOCTYPE html>
+<html lang="en">
+<head>
+    <meta charset="UTF-8">
+    <title>angel_validate</title>
+    <meta name="viewport"
+          content="width=device-width, user-scalable=no, initial-scale=1.0, maximum-scale=1.0, minimum-scale=1.0">
+    <style>
+        #errors li {
+            color: red;
+        }
+
+        #errors li.success {
+            color: green;
+        }
+    </style>
+</head>
+<body>
+<h1>Passport Registration</h1>
+<i>Validation Example</i>
+<ul id="errors"></ul>
+<form id="form">
+    <input placeholder="First Name*" name="firstName" type="text">
+    <input placeholder="Last Name*" name="lastName" type="text">
+    <br><br>
+    <input placeholder="Age*" name="age" type="number">
+    <br><br>
+    <input placeholder="Family Size" name="familySize" type="number">
+    <br><br>
+    <input placeholder="LEAVE THIS BLANK" name="blank">
+    <br><br>
+    <input type="submit" value="Submit">
+</form>
+<script src="main.dart" type="application/dart"></script>
+<script src="packages/browser/dart.js"></script>
+</body>
+</html>

web/main.dart

@@ -0,0 +1,65 @@
+import 'dart:html';
+import 'package:angel_validate/angel_validate.dart';
+
+final UListElement $errors = querySelector('#errors');
+final FormElement $form = querySelector('#form');
+final InputElement $blank = querySelector('[name="blank"]');
+
+final Validator formSchema = new Validator({
+  'firstName*': [isString, isNotEmpty],
+  'lastName*': [isString, isNotEmpty],
+  'age*': [isInt, greaterThanOrEqualTo(18)],
+  'familySize': [isInt, greaterThanOrEqualTo(1)],
+  'blank!': []
+}, defaultValues: {
+  'familySize': 1
+}, customErrorMessages: {
+  'age': (age) {
+    if (age is int && age < 18)
+      return 'Only adults can register for passports. Sorry, kid!';
+    else if (age == null || (age is String && age.trim().isEmpty))
+      return 'Age is required.';
+    else
+      return 'Age must be a positive integer. Unless you are a monster...';
+  },
+  'blank':
+      "I told you to leave that field blank, but instead you typed '{{value}}'..."
+});
+
+main() {
+  $form.onSubmit.listen((e) {
+    e.preventDefault();
+    $errors.children.clear();
+
+    var formData = {};
+
+    ['firstName', 'lastName', 'age', 'familySize'].forEach((key) {
+      formData[key] = (querySelector('[name="$key"]') as InputElement).value;
+    });
+
+    if ($blank.value.isNotEmpty) formData['blank'] = $blank.value;
+
+    print('Form data: $formData');
+
+    try {
+      var passportInfo =
+          formSchema.enforceParsed(formData, ['age', 'familySize']);
+
+      $errors.children
+        ..add(success('Successfully registered for a passport.'))
+        ..add(success('First Name: ${passportInfo["firstName"]}'))
+        ..add(success('Last Name: ${passportInfo["lastName"]}'))
+        ..add(success('Age: ${passportInfo["age"]} years old'))
+        ..add(success(
+            'Number of People in Family: ${passportInfo["familySize"]}'));
+    } on ValidationException catch (e) {
+      $errors.children.addAll(e.errors.map((error) {
+        return new LIElement()..text = error;
+      }));
+    }
+  });
+}
+
+LIElement success(String str) => new LIElement()
+  ..classes.add('success')
+  ..text = str;