Laravel Polymorphic Relations Has Many Through

问题

I have a Subscriber Model

// Subscriber Model

id
user_id
subscribable_id
subscribable_type

public function user()
{
    return $this->belongsTo('App\User');
}

public function subscribable()
{
    return $this->morphTo();
}

And a Topic Model

// Topic Model

public function subscribers()
{
    return $this->morphMany('App\Subscriber', 'subscribable');
}

And I want get all users through subscriber model, to notify them like

Notification::send($topic->users, new Notification($topic));

// Topic Model


public function users()
{
    return $this->hasManyThrough('App\User', 'App\Subscriber');
}

Any ideas?

回答1:

// Topic Model

public function users()
{
    return $this->hasManyThrough('App\User', 'App\Subscriber', 'subscribable_id')->where('subscribable_type', array_search(static::class, Relation::morphMap()) ?: static::class);
}

Polymorphic hasManyThrough relationships are the same as any others, but with an added constraint on the subscribable_type, which can be retrieved from the Relation::morphMap() array, or by using the class name directly.

回答2:

In addition to Matt's approach, the following code also could be another solution:

//Topic Model
public function users()
{
    return $this->belongsToMany(User::class, 'subscribers', 'subscribale_id', 'user_id')
        ->where('subscribale_type', static::class);
}

In this way Subscriber treated as a pivot table and second argument is table name for pivot.

The third argument is the foreign key name of the model on which you are defining the relationship, while the fourth argument is the foreign key name of the model that you are joining to. Read more here.

Consider the where clause after belongsToMany to filter only the current model.

回答3:

What you're after is not hasManyThrough, but morphedByMany.

hasManyThrough is useful when you have A one-to-many B, B one-to-many C, and you want to use A to fetch many C.

What you have is a polymorphic pivot table sitting in the middle between A and C.

// Topic Model

public function users()
{
    return $this->morphedByMany('App\User', 'subscribable', 'pivot/subscriber_table_name');
}

Docs: https://laravel.com/docs/6.x/eloquent-relationships#many-to-many-polymorphic-relations

回答4:

Ok, i got a better solution

// Subscriber Model

use Notifiable;

public function receivesBroadcastNotificationsOn()
{
    return 'App.User.' . $this->user_id;
}


// Send Notification

Notification::send($post->subscribers, new TestNotification($post));

来源：https://stackoverflow.com/questions/43285779/laravel-polymorphic-relations-has-many-through

标签

php

laravel

relationship

has-many-through