Codeigniter如果没有设置uri_to_assoc参数如何找到它

Inside of codeigniter controller I want to find whether uri_to_assoc values are set properly. If no I want to display a proper error message. So can someone please explain me how to find that. Please look example below,

when values set properly,

www.example.com/features/edit/8

when not set,

www.example.com/features/edit/

You have to check every value starting from the second segment.

In the controller:

public function _checkUriSegments(){
    $params = $this->uri->uri_to_assoc(2);
    var_dump($params);
    foreach ($params as $key => $value) {
        if(!$params[$key]){
            return false;
        }
    }
    return true;
}

public function edit(){
    if(!$this->_checkUriSegments()){
        echo 'wrong url !';
        break;
    }
    // do some edits
}