Yii2 relations with junction table - yii2

Question

I have free tables: user, book, user_book, offers
user table has method:
public function getBooks()
{
return $this->hasMany(UserBook::className(), ['user_id' => 'id']);
}
user_book table has two fields: user_id, book_id; and methods
public function getUser()
{
return $this->hasOne(User::className(), ['id' => 'user_id']);
}
public function getBook()
{
return $this->hasOne(Book::className(), ['id' => 'book_id']);
}
table offer have method like: getUser(), getBook(),
and now I would like show Books which user don't have. I try do something like
$query = Offer::find()
->with('user')
->andWhere([
'offer.status' => Offer::STATUS_ACTIVE,
]);
$query->andWhere(['not in', 'offer.book_id', 'user.books.book_id']);
but it doesn't work. Do you have some ideas how can I make it?

Answer 1

Yii2 docs, relation via junction table
In database modelling, when the multiplicity between two related
tables is many-to-many, a junction table is usually introduced. For
example, the order table and the item table may be related via a
junction table named order_item. One order will then correspond to
multiple order items, while one product item will also correspond to
multiple order items.
When declaring such relations, you would call either via() or
viaTable() to specify the junction table. The difference between via()
and viaTable() is that the former specifies the junction table in
terms of an existing relation name while the latter directly uses the
junction table. For example,
class Order extends ActiveRecord
{
public function getItems()
{
return $this->hasMany(Item::className(), ['id' => 'item_id'])
->viaTable('order_item', ['order_id' => 'id']);
}
}
or alternatively,
class Order extends ActiveRecord
{
public function getOrderItems()
{
return $this->hasMany(OrderItem::className(), ['order_id' => 'id']);
}
public function getItems()
{
return $this->hasMany(Item::className(), ['id' => 'item_id'])
->via('orderItems');
}
}