cakehp2.3-更改密码方法错误

我在控制器（UsersController.php）中有一种更改用户密码的方法：

public function changepass() {
    if($this->User->exists()) {         
        $new_pass = $this->request->data['User']['newpass'];
        $repeat_pass = $this->request->data['User']['newrepeat'];
            if($new_pass == $repeat_pass) {
                $this->User->saveField('password',$new_pass);
                $this->Session->flash(__('Updated successfully'));
                $this->redirect(array('controller' => 'users','action' => 'dashboard'));
            } else {
                $this->Session->flash(__('Passwords did not match'));
                $this->redirect(array('controller' => 'users','action' => 'changepass'));
            }
    }
}

这个视图（changepass.ctp）：

<?php 
    echo $this->Form->create();
    echo $this->Form->input('newpass',array('type'=>'text','label'=>array('text'=>'Enter new password'))); 
    echo $this->Form->input('newrepeat',array('type'=>'text','label'=>array('text'=>'Confirm new password'))); 
?>
    <button type="submit">Save</button>
<?php echo $this->Form->end(); ?>

但这似乎不起作用，我真的不明白为什么。你能帮我吗？你看到这里出了什么问题吗？

提前谢谢各位！