Laravel, querying through many-to-many relationships

Question

I have some trouble with Laravel and many to many relationships.

I have the following structure: Sensor -> sensor group -> usages

so a sensor can belong to many groups, and a group can have multiple "usages".

The sensor class looks like this:

class sensor extends Model {

protected $table = 'sensor';
protected $primaryKey = 's_id';

public function groups()
    {
     return $this->belongsToMany('App\sensorgroup','sensor_sensorgroup','ssg_s_id','ssg_sg_id');
    }
}

the sensorgroup class looks like this:

class sensorgroup extends Model {

    protected $table = 'sensorgroup';
    protected $primaryKey = 'sg_id';

    public function sensors()
    {
        return $this->belongsToMany('App\sensor', 'sensor_sensorgroup','ssg_sg_id','ssg_s_id');
    }

    public function usages()
    {
        return $this->belongsToMany('App\sensorgroupUsage','sensorGroup_sensorGroupUsage','sgsgu_sg_id','sgsgu_sgu_id');
    }
}

and the usages class looks like this:

class sensorgroupUsage extends Model {

    protected $table = 'SensorGroupUsage';
    protected $primaryKey = 'sgu_id';
    protected $fillable = ['sg_name'];

    public function sensorgroups()
    {
        return $this->belongsToMany('App\sensorgroup','sensorGroup_sensorGroupUsage','sgsgu_sgu_id','sgsgu_sg_id');
    }

}

Now I want to get all groups for a sensor, but only if that sensor group is attached to some specific "usage".

To get all sensorgroups for one sensor, I can use this:

$sensor = App\sensor::find($sensorId);
$groups = $sensor->groups();

I can't however figure out how to add the condition to only get the sensor groups that are attached to a specific usage. Any ideas?

Answer 1

Use whereHas method

$usergesId = //here must be an array with useges id
$sensor = App\sensor::find($sensorId);
$groups = $sensor->groups()->whereHas('usages', function ($query) use($usergesId) {
    $query->whereIn('sgu_id', $usagesId);
})->get();