Get attributes of model in init at behavior yii2 - yii2

Question

Here is my code:
class CalculatedFieldsBehavior extends Behavior {
public $calcFields = array();
public function events() {
return [
ActiveRecord::EVENT_INIT => 'init',
];
}
public function init() {
foreach ($this->owner->attributes() as $attribute) {
if (strpos($attribute, 'calc_')) {
if (!is_function(get_parent_class()::$set . \yii\helpers\camelize($attribute))) {
throw Exception("Function to set value of calc field '" . $attribute . "' not defined.");
}
$calcFields[] = $attribute;
}
}
if (!($this->owner->hasAttribute('isCalcValueSet'))) {
throw Exception("This table is missing a field for isCalcValueSet");
}
parent::init();
}
}
And give this error:
"name": "Exception",
"message": "Call to a member function attributes() on null",
"code": 0,
"type": "Error",
"file": "D:\\xampp\\htdocs\\backoffice\\common\\models\\CalculatedFieldsBehavior.php",
"line": 25,

Answer 1

$owner is not available in init(). It is set in attach(). Usually workflow looks like this:
$behavior = new MyBehavior(); // init() is called here
$behavior->attach($owner); // owner is set here
You should probably overwrite attach() in your case:
public function attach($owner) {
foreach ($owner->attributes() as $attribute) {
if (strpos($attribute, 'calc_')) {
if (!is_function(get_parent_class()::$set . \yii\helpers\camelize($attribute))) {
throw Exception("Function to set value of calc field '" . $attribute . "' not defined.");
}
$calcFields[] = $attribute;
}
}
if (!($owner->hasAttribute('isCalcValueSet'))) {
throw Exception("This table is missing a field for isCalcValueSet");
}
parent::attach($owner);
}