如何通过 pivot 表中的列过滤多对多关系

Question

My application has the following entities:

• Locations
• Disciplines
• Instructors

Disciplines and Instructors should be a many to many relationship, so in my Discipline model I have the following:

public function instructors() {
    return $this->belongsToMany(
        Instructor::class,
        'location_discipline_instructors',
        'discipline_id',
        'instructor_id'
    );
}

My pivot table contains the following fields:

• location_id
• discipline_id
• instructor_id

I can use this relationship to fetch all disciplines with the associated instructors , but I need to filter these results by the location_id in the pivot table.

How should I approach this?

Answer 1

I tried using wherePivot() with location_id , but with that approach, I ended up with a list of all system disciplines with instructors for any discipline that had instructors associated. I continued to research and ended up with this solution:

Discipline::whereHas('instructors', function ($query) {
    return $query->where('location_id', '=', $this->locationId);
})->with('instructors')->get();