php 我如何在 Yii2 中处理多对多关系
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How do I work with many-to-many relations in Yii2
提问by raiym
For example in one-to-many due to documentation (http://www.yiiframework.com/doc-2.0/guide-db-active-record.html#relational-data) you can link two models in this way (one-many = company-zone):
例如，由于文档（http://www.yiiframework.com/doc-2.0/guide-db-active-record.html#relational-data）的一对多，您可以通过这种方式链接两个模型(one-many = company-zone)：
$defaultZone = new Zone;
$defaultZone->name = Zone::DEFAULT_ZONE;
$company->link('zones', $defaultZone);
But how it works for many-to-many relations when you have transit table like tbl_user_market(user_id, market_id)?
但是，当您有像这样的中转表时，它如何适用于多对多关系tbl_user_market(user_id, market_id)？
回答by vim
When using a junction table for many-to-many relations, you have to
将联结表用于多对多关系时，您必须
- Define the relations
- Link the two models together
- 定义关系
- 将两个模型连接在一起
In the User model define the following relation function:
在 User 模型中定义以下关系函数：
public function getMarkets() {
return $this->hasMany(Market::className(), ['id' => 'market_id'])
->viaTable('tbl_user_market', ['user_id' => 'id']);
}
In the Market model define the following relation function:
在市场模型中定义以下关系函数：
public function getUsers() {
return $this->hasMany(User::className(), ['id' => 'user_id'])
->viaTable('tbl_user_market', ['market_id' => 'id']);
}
And finally, after saving both models, link them together:
最后，在保存两个模型后，将它们链接在一起：
$user = new User;
$user->name = 'Foo';
$user->save();
$market = new Market;
$market->name = 'Bar';
$market->save();
$user->link('markets', $market);
The call to link()will populate the junction table.
调用link()将填充联结表。
Reference: http://www.yiiframework.com/doc-2.0/yii-db-baseactiverecord.html#link()-detail
参考：http: //www.yiiframework.com/doc-2.0/yii-db-baseactiverecord.html#link()-detail
