eloquent sum of relation's column in single query - laravel

Question

in this query i have three table such as radio, radio_channels and radio_channels_files which into that i want to calculate one column which that is into radio_channels_files table as new column such as duration_sum, my below code work but i can't calculate this column
class Radio extends Model
{
use SoftDeletes;
protected $guarded = ['id'];
protected $casts = [
'logo_path' => 'array',
'cover_path' => 'array'
];
public function category()
{
return $this->belongsTo(RadioCategory::class);
}
public function channels()
{
return $this->hasMany(RadioChannels::class);
}
}
class RadioChannelsFiles extends Model
{
protected $guarded = ['id'];
protected $casts = [
'image' => 'array',
//'keywords' => 'array',
];
public function channel()
{
return $this->belongsTo(RadioChannels::class,'playlist_id');
}
}
class RadioChannels extends Model
{
protected $guarded = ['id'];
protected $casts = [
'image' => 'array'
];
public function channel()
{
return $this->belongsTo(Radio::class);
}
public function files()
{
return $this->hasMany(RadioChannelsFiles::class , 'playlist_id');
}
public function duration_sum()
{
return $this->hasOne(RadioChannelsFiles::class ,'playlist_id')
->select('duration',
DB::raw('sum(duration)')
)->groupBy('duration');
}
}
$channels = Radio::with(['category', 'channels' => function ($query) {
$query->with(['files','duration_sum']);
}])->paginate(50);
i get null output:
#relations: array:2 [▼
"files" => Illuminate\Database\Eloquent\Collection {#1422 ▶}
"duration_sum" => null //should return sum of duration from files
]

Answer 1

i figured out how can i get it
public function getRadiosList(Request $request)
{
$radios = Radio::with(['category', 'playLists' => function ($query) {
$query->with(['files','duration_sum']);
}])->get();
return response()->json(['data' => $radios, 'statusCode' => 1], 200);
}
model:
public function duration_sum()
{
return $this->hasOne(RadioPlaylistsFiles::class, 'playlist_id')
->select('playlist_id',
DB::raw('sum(duration) as `all_duration`')
)->groupBy('playlist_id');
}