在cakehp3中保存数据

我想将用户数据保存在数据库中，但仍收到错误

数据

$this->request->data['nickname'] = ' asd';
$this->request->data['first_name'] = ' asd';
$this->request->data['last_name'] = 'asd ';

控制器

$user = $this->Users->newEntity();
$user = $this->Users->patchEntity($user, $this->request->data);
if ($this->Users->save($user)) {
       echo 'saved';
} else {
       echo 'error';
}