HTTP POST request return attempt to insert nil object from objects[0] ?

Question

I'm trying to send an http request to the server where I need to send the following required parameters

description:string, amount: float, occurred_at: string,location: string

As the amount I need to pass it through a textfield (the other fields are coming through an API) has been made a Segue passing the PreObject object to that view whose amount is needed.

Magical Record is using for objects

PreObject

( (entity: PreObject; id: 0xd000000000040006 ; data: { amount = nil; creatingOnBackend = 1; currency = nil; description = ""; expense = nil; extraInformation = "0xd000000001400010 "; identifier = 47; ignoredAt = nil; location = nil; occuredAt = "2017-03-12 00:00:00 +0000"; participants = ""; payer = nil; receiver = nil; status = nil; tags = ""; }))

Http Request requisition:

 class  func sendToBackend(object: PreObject,preObjectID: NSNumber, withCompletion completion: (error: NSError?) -> ()) {

        let url = "\(ServicesUtils.baseUrl())/objects/\(preObjectID)/send"
        let params = [object.dictionaryBackend()]
        let sessionManager = ServicesUtils.rexpenseBaseSessionManager()
        let request = sessionManager.requestSerializer.requestWithMethod("POST", URLString: url, parameters: params, error: nil)


        let task = sessionManager.dataTaskWithRequest(request) { urlResponse, responseObject, error in
            if let _ = error {
                let returnError = ServicesUtils.rexpenseHandleErrorWithResponse(urlResponse, andRequest: request, andResult: responseObject)
                completion(error: returnError)
                return

            }

            guard let dict = responseObject as? [String: AnyObject] else {
                let errorMessage = "Error"
                let error = NSError(domain: "xxxxxxxxx", code: -1, userInfo: [NSLocalizedDescriptionKey : errorMessage])
                completion(error: error)
                return


            }

            let moc = NSManagedObjectContext.MR_defaultContext()
            PreObject.createPreObjectwithDictionary(dict, inContext: moc)
            moc.MR_saveToPersistentStoreAndWait()
            completion(error: nil)
        }
        task.resume()
    }

Dictionary that pass in parameters of requisition:

- (NSMutableDictionary *)dictionaryBackend {

    NSMutableDictionary *dict = [[NSMutableDictionary alloc] init];

    dict[@"description"] = description == nil ? [NSNull null] : description;
    dict[@"payer"] = @{@"id": self.payer.identifier,
                       @"type": @"xxxxx"};

    if ([self.amount doubleValue] == [self.amount intValue]) {
        NSNumber *number = [NSNumber numberWithDouble:[self.amount doubleValue] + 0.001];
        dict[@"amount"] = number;

    } else {
        dict[@"amount"] = self.amount;
    }

    NSDateFormatter *dateFormatter = [ServicesUtils defaultDateFormatter];
    dict[@"occurred_at"] = [dateFormatter stringFromDate:self.occuredAt];

    dict[@"tags"] = [self tagsSeparatedByComma];
    dict[@"location"] = self.address == nil ? [NSNull null] : self.address;
    dict[@"currency"] = self.currency;

           return dict;

When i tap in UIButton app crash and show this error on debug area:

* Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '* -[__NSPlaceholderDictionary initWithObjects:forKeys:count:]: attempt to insert nil object from objects[0]'

Someone can help me?

Answer 1

This crash is generally caused by trying to create a dictionary with nil values.

Check before the line:

dict[@"payer"] = @{@"id": self.payer.identifier,
                   @"type": @"xxxxx"};

if self.player.identifier is nil.

I cannot advice what you should when it is nil, because that can mean different things in different applications.