Error when uploading image on database "Call to a member function getClientOriginalName() on string"

i have problem when upload image on database. the error is "Call to a member function getClientOriginalName() on string". Please help me to solve my error. TQ

{
    // $this->validate($request, [
    //     //
    // ]);

    if ($request->file) {

        $filename = uniqid() . '_' . $request->file->getClientOriginalName();

        $request->file->move(public_path('img/staf'), $filename); //upload picture on database

        $data->store($request->all() + ['gambar' => $filename]);

    } else {
        $data = Pekerja::create($request->all());
    }

    return redirect()->to($request->prev_url)
                     ->with('Success','Pekerja Berjaya Ditambah!');
}

via Chebli Mohamed