public function primary()
    {
        $columns = array_filter($this->_props, function($property) {
            return $property->type->options()->primary;
        });

        if(empty($columns))
            throw new Exception("No primary key defined for {$this->_class}");

        return $columns;
    }
public function primary()
    {
        $columns = array_filter($this->_props, function($property) {
            return $property->type->options()->primary;
        });

        if(empty($columns))
            throw new Exception("No primary key defined for {$this->_class}");

        return $columns;
    }
public function primary ( ) { $ columns = array_filter ( $ this -> _props , function ( $ property ) { return $ property -> type -> options ( ) -> primary ; } ) ; if ( empty ( $ columns ) ) throw new Exception ( "No primary key defined for {$this->_class}" ) ; return $ columns ; }
Returns an array of Properties that form the primary keys
@return array
Returns an array of Properties that form the primary keys