inheritance - Derived classes with ActiveRecord in Yii -

i working following database design, , wanted understand how can best address in yii.

+---------------+----------------+---------------------+ |     table     |  column name   |     column type     | +---------------+----------------+---------------------+ | question      | id             | int                 | |               | description    | text                | |               | type           | enum('mcq', 'text') | |               |                |                     | |               |                |                     | | mcq_question  | id             | int                 | |               | question_id    | int                 | |               | option1        | text                | |               | option2        | text                | |               | option3        | text                | |               | option4        | text                | |               | correct_answer | option1             | |               |                |                     | |               |                |                     | | text_question | id             | int                 | |               | question_id    | int                 | |               | answer         | text                | +---------------+----------------+---------------------+ 

the idea have different kind of questions mcq, text, grid, true/false etc. common data can captured in "question" table, while specifics can captured in respective tables. in simple programming concepts, easy map structure "question" class base class other classes "mcq_question", "text_question" etc. types of such questions may increase in future, hence need flexibility.

with above approach, can use "question_id" foreign key relationships other tables, rather working each individual table, make code more complex.

from understood reading of articles, approach doesn't work yii: http://www.yiiframework.com/forum/index.php/topic/23405-cactiverecord-inheritance-and-dynamic-attributes/

is there no way yii? if not, of workarounds problem keep code simple.

regards, kapil

the link refer not apply question. can create derived classes , override tablename()-function load out of correct table.

first of all, in situation not use different ids derived types, use same id. 1 question_id lot easier maintain (and store answers for). remove auto_increment derived tables id field , remove question_id. assuming that:

a minimalised example mcq_question:

class mcq_question extends question {    public $description = '';    public $type = 'mcq';     function tablename()    {       return 'mcq_question';    } } 

there 2 issues remaining: 1) generic function in base class loads specific question 2) if save derived class, should update/create question instance

1) easy, might have add array "convert" between enum , class name:

class question extends cactiverecord {    public function findbyid($questionid)    {       $types = array('mcq' => 'mcq_question');       $question = $this->findbypk($questionid);       if ($question && array_key_exists($question->type, $types)       {          $class = $types[$question->type];          return $class::model()->findbypk($question->id);       }    } } 

the array links not graceful solution, trick. can add static it's more clear have updated, , on.

2) can accomplish overriding beforesave()-function in derived classes.

  public function beforesave()   {      if ($this->isnewrecord)      {         $question = new question();         $question->type = $this->type;         $question->description = $this->description;         $question->save();         $this->id = $question->id;      }      // else check if perhaps description changed , update     ... 

this not code need again, it's not job yours ;)

it should started though. beforesave end pretty same everywhere if php recent enough, in trait.