php - Yii2 set new active record relation on init -

i have one-to-one relationship, there fields thing in table thingextra.

i'm trying initialise new thingextra work when creating new thing, , save them both when thing saved:

class thing extends activerecord {     public function init(){         if($this->isnewrecord){             $this->extra = new thingextra();         }     }      public function getextra(){         return $this->hasone(thingextra::classname(),['thing_id' => 'id']);     }      public function aftersave($insert, $changedattributes)     {         parent::aftersave($insert, $changedattributes);         $this->extra->thing_id = $this->id;         $this->extra->save();     } } 

now when try create thing:

$thing = new thing; 

i following exception:

exception: setting read-only property: thing::extra 

is there anyway round this? or design utterly flawed?

this approach worked pretty in yii1.1

you cannot assign relation this, try instead :

public function init(){     if($this->isnewrecord){         $this->populaterelation('extra', new thingextra());     } } 

read more activerecord::populaterelation()