Laravel口才如何建立逆向关系？

Question

I have two models/tables: publisher and campaign.

Publisher

id | name

Campaign

id | name | PubID

I created a relationship to get the Publisher's campaigns.

$this->hasMany(Campaign::class, 'PubID'); /* In Publisher Model */

I believe the above line will help me to retrieve relevant campaigns, but I'm confused about the inverse relationship.

As you can see, there is no key campaign_id inside the publisher table. Would the below relationship be enough for the inverse?

return $this->belongsTo('App\Publisher'); /* In Campaign Model */

Can someone kindly guide me? I would appreciate it.

Answer 1

Yes, this is so called one to many relationship , which means one publisher has many campaigns. And the inverse is that a campaign belongs to a publisher. So in order to get all the campaigns for the publisher you use:

Publisher::find($id)->campaigns;

In order to get what is the publisher of the campaign, you use:

Campaign::find($id)->publisher;

You don't need campaign_id inside the publisher table, that is known by the PubID in your campaign table.

Answer 2

You ,eed to specify the foreign key name in the belongsTo

return $this->belongsTo('App\Publisher','PubID');

Laravel Relationships

Answer 3

You have two models and adding two foreign id. It is a many to many working. You just need add pivot table with campain_id and publiser_id

It's a perfect example of many-to-many relationship: one publisher can belong to several campains, and one campains can have multiple publisher.

publishers

ID | NAME

campaigns

ID | NAME

campaign_publisher

campain_id | publisher_id

The final table in the list – campaign_publisher is called a “pivot” table, as mentioned in the topic title.

So, option 1:

class Campaign extends Model
{
    /**
     * The products that belong to the shop.
     */
    public function publishers()
    {
        return $this->belongsToMany('App\Publisher');
    }
}

So, option 2:

class Publisher extends Model
{
    /**
     * The shops that belong to the product.
     */
    public function campaigns()
    {
        return $this->belongsToMany('App\Campaign');
    }
}