enhanced the usage of StringValidator.

docs/guide/model.md

@@ -237,8 +237,8 @@ function rules()
 {
 	return array(
 		// rule applied when corresponding field is "safe"
-		array('username', 'string', 'min' => 2),
-		array('first_name', 'string', 'min' => 2),
+		array('username', 'string', 'length' => array(4, 32)),
+		array('first_name', 'string', 'max' => 128),
 		array('password', 'required'),
 
 		// rule applied when scenario is "signup" no matter if field is "safe" or not

framework/yii/validators/StringValidator.php

@@ -21,17 +21,24 @@ use yii\helpers\Html;
 class StringValidator extends Validator
 {
 	/**
-	 * @var integer maximum length. Defaults to null, meaning no maximum limit.
+	 * @var integer|array specifies the length limit of the value to be validated.
+	 * This can be specified in one of the following forms:
+	 *
+	 * - an integer: the exact length that the value should be of;
+	 * - an array of one element: the minimum length that the value should be of. For example, `array(8)`.
+	 *   This will overwrite [[min]].
+	 * - an array of two elements: the minimum and maximum lengths that the value should be of.
+	 *   For example, `array(8, 128)`. This will overwrite both [[min]] and [[max]].
 	 */
-	public $max;
+	public $length;
 	/**
-	 * @var integer minimum length. Defaults to null, meaning no minimum limit.
+	 * @var integer maximum length. If not set, it means no maximum length limit.
 	 */
-	public $min;
+	public $max;
 	/**
-	 * @var integer exact length. Defaults to null, meaning no exact length limit.
+	 * @var integer minimum length. If not set, it means no minimum length limit.
 	 */
-	public $is;
+	public $min;
 	/**
 	 * @var string user-defined error message used when the value is not a string
 	 */
@@ -61,6 +68,15 @@ class StringValidator extends Validator
 	public function init()
 	{
 		parent::init();
+		if (is_array($this->length)) {
+			if (isset($this->length[0])) {
+				$this->min = $this->length[0];
+			}
+			if (isset($this->length[1])) {
+				$this->max = $this->length[1];
+			}
+			$this->length = null;
+		}
 		if ($this->encoding === null) {
 			$this->encoding = Yii::$app->charset;
 		}
@@ -73,7 +89,7 @@ class StringValidator extends Validator
 		if ($this->max !== null && $this->tooLong === null) {
 			$this->tooLong = Yii::t('yii', '{attribute} should contain at most {max} characters.');
 		}
-		if ($this->is !== null && $this->notEqual === null) {
+		if ($this->length !== null && $this->notEqual === null) {
 			$this->notEqual = Yii::t('yii', '{attribute} should contain {length} characters.');
 		}
 	}
@@ -101,8 +117,8 @@ class StringValidator extends Validator
 		if ($this->max !== null && $length > $this->max) {
 			$this->addError($object, $attribute, $this->tooLong, array('{max}' => $this->max));
 		}
-		if ($this->is !== null && $length !== $this->is) {
-			$this->addError($object, $attribute, $this->notEqual, array('{length}' => $this->is));
+		if ($this->length !== null && $length !== $this->length) {
+			$this->addError($object, $attribute, $this->notEqual, array('{length}' => $this->length));
 		}
 	}
 
@@ -119,7 +135,7 @@ class StringValidator extends Validator
 		$length = mb_strlen($value, $this->encoding);
 		return ($this->min === null || $length >= $this->min)
 			&& ($this->max === null || $length <= $this->max)
-			&& ($this->is === null || $length === $this->is);
+			&& ($this->length === null || $length === $this->length);
 	}
 
 	/**
@@ -158,8 +174,8 @@ class StringValidator extends Validator
 				'{max}' => $this->max,
 			)));
 		}
-		if ($this->is !== null) {
-			$options['is'] = $this->is;
+		if ($this->length !== null) {
+			$options['is'] = $this->length;
 			$options['notEqual'] = Html::encode(strtr($this->notEqual, array(
 				'{attribute}' => $label,
 				'{value}' => $value,