User orderby its activities

[mahboobsabiry]

Hello everyone,
I hope you all OK.
I want orderBy users by counting all its activities. Like: User::orderBy(count($this->activities()), 'desc')->take(10);
My User Model: public function activities () {return Activity::all()->where('causer_id', $this->id)->count();} and my controller: User::all()->orderBy(count($this->activities()), 'desc)->take(10);
But it doesn't work.
Any help please