Exception 'ReflectionException' with message 'Class require does not exist'

 记录一下今天遇到的错误

在使用

<?= $form->field($model, 'content')->textarea() ?>

的时候报错

Exception 'ReflectionException' with message 'Class require does not exist'

in D:\phpStudy\WWW\vvv\vendor\yiisoft\yii2\di\Container.php:415

Stack trace:
#0 D:\phpStudy\WWW\clecssv2\vendor\yiisoft\yii2\di\Container.php(415): ReflectionClass->__construct('require')
#1 D:\phpStudy\WWW\clecssv2\vendor\yiisoft\yii2\di\Container.php(358): yii\di\Container->getDependencies('require')
#2 D:\phpStudy\WWW\clecssv2\vendor\yiisoft\yii2\di\Container.php(151): yii\di\Container->build('require', Array, Array)
#3 D:\phpStudy\WWW\clecssv2\vendor\yiisoft\yii2\BaseYii.php(344): yii\di\Container->get('require', Array, Array)
#4 D:\phpStudy\WWW\clecssv2\vendor\yiisoft\yii2\validators\Validator.php(206): yii\BaseYii::createObject(Array)

错误原因是：

public function rules()
{
　　return [
　　[['content'],'require'],
　　];
}
少了一个d, required