public static function update(WaterPriceRequest $request, $id)
 {
     $price = WaterPrice::find($id);
     if (!$price) {
         return redirect()->back()->withInput()->withErrors('No se ha encontro el registro seleccionado');
     }
     if ($request->input('active') == '') {
         //debe existir al menos un precio activo
         $active = WaterPrice::whereNotIn('id', [$id])->active()->first();
         if (!$active) {
             return redirect()->back()->withInput()->withErrors('Debe haber al menos un registro de precio ACTIVO');
         }
     }
     $price->description = $request->input('description');
     $price->price = $request->input('price');
     $price->active = $request->input('active');
     $price->save();
     return redirect()->route('water-prices.index')->with('success', 'El registro ha sido almacenado correctamente');
 }