ParseManager.sharedManager().fetchPrice(startDate: startDate, endDate: endDate, housingId: housing.objectId!) { (objects, error) in
    if (objects != []) {
        var price = 0

     for object in objects! {
         price += object["prix"] as! Int
     }
     price /= objects!.count
     self.priceByNight.text = "Price: (price)"
    }
}

func fetchPrice(startDate: Date, endDate: Date, housingId: String, completion: PFResults?) {
 let params = [
    "startDate": startDate,
    "endDate": endDate,
    "logement": housingId
 ] as [String : Any]

 PFCloud.callFunction(inBackground: "fetchPrice", withParameters: params) { (objects, error) in
    if let error = error {
        print(error)
        completion?(nil, error)
        return
    }

    if let objects = objects as? [PFObject] {
        completion?(objects, nil)
    }
 }
}