'NSInvalidArgumentException', reason: '*** -[__NSPlaceholderDictionary initWithObjects:forKeys:count:]: attempt to insert nil object from objects[3]'

I have two UITextFields in my storyboard that are meant to take in a number that the user inputs, a minPrice and maxPrice. When I click submit in the simulator, the app crashes and I receive the following error:

Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '*** -[__NSPlaceholderDictionary initWithObjects:forKeys:count:]: attempt to insert nil object from objects[3]'
*** First throw call stack:
(
    0   CoreFoundation                      0x02a881e4 __exceptionPreprocess + 180
    1   libobjc.A.dylib                     0x026468e5 objc_exception_throw + 44
    2   CoreFoundation                      0x02a4e376 -[__NSPlaceholderDictionary initWithObjects:forKeys:count:] + 390
    3   CoreFoundation                      0x02a7bc29 +[NSDictionary dictionaryWithObjects:forKeys:count:] + 73
    4   Parse+Storyboard                    0x0000b5b5 -[CriteriaViewController submitButton:] + 757
    5   libobjc.A.dylib                     0x02658880 -[NSObject performSelector:withObject:withObject:] + 77
    6   UIKit                               0x013083b9 -[UIApplication sendAction:to:from:forEvent:] + 108
    7   UIKit                               0x01308345 -[UIApplication sendAction:toTarget:fromSender:forEvent:] + 61
    8   UIKit                               0x01409bd1 -[UIControl sendAction:to:forEvent:] + 66
    9   UIKit                               0x01409fc6 -[UIControl _sendActionsForEvents:withEvent:] + 577
    10  UIKit                               0x01409243 -[UIControl touchesEnded:withEvent:] + 641
    11  UIKit                               0x01347ddd -[UIWindow _sendTouchesForEvent:] + 852
    12  UIKit                               0x013489d1 -[UIWindow sendEvent:] + 1117
    13  UIKit                               0x0131a5f2 -[UIApplication sendEvent:] + 242
    14  UIKit                               0x01304353 _UIApplicationHandleEventQueue + 11455
    15  CoreFoundation                      0x02a1177f __CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE0_PERFORM_FUNCTION__ + 15
    16  CoreFoundation                      0x02a1110b __CFRunLoopDoSources0 + 235
    17  CoreFoundation                      0x02a2e1ae __CFRunLoopRun + 910
    18  CoreFoundation                      0x02a2d9d3 CFRunLoopRunSpecific + 467
    19  CoreFoundation                      0x02a2d7eb CFRunLoopRunInMode + 123
    20  GraphicsServices                    0x02ce55ee GSEventRunModal + 192
    21  GraphicsServices                    0x02ce542b GSEventRun + 104
    22  UIKit                               0x01306f9b UIApplicationMain + 1225
    23  Parse+Storyboard                    0x000020ed main + 141
    24  libdyld.dylib                       0x038e2701 start + 1
)
libc++abi.dylib: terminating with uncaught exception of type NSException
(lldb) 

CriteriaViewController.h:

#import <UIKit/UIKit.h>
#import <Parse/Parse.h>
#import "SearchViewController.h"

@interface CriteriaViewController : UIViewController{

IBOutlet UISegmentedControl *Segment;
}


//@property (nonatomic) IBOutlet UITextField *itemSearch;
@property (weak, nonatomic) IBOutlet UITextField *minPrice;
@property (weak, nonatomic) IBOutlet UITextField *maxPrice;
@property (nonatomic, copy) NSNumber *chosenCategory;
@property (weak, nonatomic) NSString *itemCondition;
@property (weak, nonatomic) NSString *itemLocation;
@property (weak, nonatomic) NSString *itemSearch;

@end

CriteriaViewController.m:

    #import "CriteriaViewController.h"

@interface CriteriaViewController ()
@property (weak, nonatomic) IBOutlet UISegmentedControl *itemConditionSegment;
@property (weak, nonatomic) IBOutlet UISegmentedControl *itemLocationSegment;


@end

@implementation CriteriaViewController

- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil
{
    self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
    if (self) {
        // Custom initialization
    }
    return self;
}

- (void)viewDidLoad
{

    [super viewDidLoad];

    // Condition UISegment
    UISegmentedControl *conditionSegmentedControl = [[UISegmentedControl alloc] initWithItems:[NSArray arrayWithObjects:@"Only New", @"Any", nil]];
    conditionSegmentedControl.frame = CGRectMake(87, 190, 157, 30);
    conditionSegmentedControl.selectedSegmentIndex = 0;
    conditionSegmentedControl.tintColor = [UIColor blackColor];
    [conditionSegmentedControl addTarget:self action:@selector(ConditionSegmentControlAction:) forControlEvents: UIControlEventValueChanged];
    [self.view addSubview:conditionSegmentedControl];


    // Location UISegment
    UISegmentedControl *locationSegmentedControl = [[UISegmentedControl alloc] initWithItems:[NSArray arrayWithObjects:@"Fast Shipping", @"Large Selection", nil]];
    locationSegmentedControl.frame = CGRectMake(67, 275, 200, 30);
    locationSegmentedControl.selectedSegmentIndex = 0;
    locationSegmentedControl.tintColor = [UIColor blackColor];
    [locationSegmentedControl addTarget:self action:@selector(LocationSegmentControlAction:) forControlEvents: UIControlEventValueChanged];
    [self.view addSubview:locationSegmentedControl];

    // Submit button
    UIButton *submitButton = [UIButton buttonWithType:UIButtonTypeRoundedRect]; // Create Round Rect Type button.
    submitButton.frame = CGRectMake(100, 100, 100, 100); // define position and width and height for the button.
    [submitButton setTitle:@"Submit" forState:UIControlStateNormal];

    [submitButton addTarget:self action:@selector(submitButton:) forControlEvents:UIControlEventTouchUpInside];
    [self.view addSubview:submitButton];

}

- (void)ConditionSegmentControlAction:(UISegmentedControl *)segment
{
    if(segment.selectedSegmentIndex == 0)
    {
        // set condition to new
        self.itemCondition = @"new";
    }
    else if (segment.selectedSegmentIndex == 1)
    {
        // set condition to all
        self.itemCondition = @"all";
    }
}

- (void)LocationSegmentControlAction:(UISegmentedControl *)segment
{
    if(segment.selectedSegmentIndex == 0)
    {
        // set location to us
        self.itemLocation = @"US";
    }
    else if (segment.selectedSegmentIndex == 1)
    {
        // set clocation to worldwide
        self.itemLocation = @"Worldwide";
    }
}


- (void)didReceiveMemoryWarning
{
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}


//add all the info to users respective new category object
- (IBAction)submitButton:(id)sender
{
    if (self.minPrice.text.length > 0 && self.maxPrice.text.length > 0) {

        [PFCloud callFunctionInBackground:@"userCategorySave"
                           withParameters:@{@"categoryId": self.chosenCategory,
                                              @"minPrice": self.minPrice,
                                            @"maxPrice": self.maxPrice,
                                       @"itemCondition": self.itemCondition,
                                        @"itemLocation": self.itemLocation
                                            }
                                         block:^(NSString *result, NSError *error) {

                                             if (!error) {
                                                 NSLog(@"Criteria successfully saved.");

                                                     [self performSegueWithIdentifier:@"SearchCategoryChooserToMatchCenterSegue" sender:self];

                                             }
                                         }];

    }

}


- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender {



    [PFCloud callFunctionInBackground:@"addToMatchCenter"
                       withParameters:@{
//                                        @"searchTerm": self.itemSearch,
                                        @"categoryId": self.chosenCategory,
//                                        @"minPrice": self.minPrice,
//                                        @"maxPrice": self.maxPrice,
//                                        @"itemCondition": self.itemCondition,
//                                        @"itemLocation": self.itemLocation,
                                        }
                                block:^(NSString *result, NSError *error) {

                                    if (!error) {
                                        NSLog(@"'%@'", result);
                                    }
                                }];

    // Get the new view controller using [segue destinationViewController].
    // Pass the selected object to the new view controller.

}



@end

Cloud Code:

Parse.Cloud.define("userCategorySave", function(request, response) {


  var userCategory = Parse.Object.extend("userCategory");
  var newUserCategory = new userCategory();
      newUserCategory.set("categoryId", request.params.categoryId);
      newUserCategory.set("minPrice", request.params.minPrice);
      newUserCategory.set("maxPrice", request.params.maxPrice);
      newUserCategory.set("itemCondition", request.params.itemCondition);
      newUserCategory.set("itemLocation", request.params.itemLocation);
      newUserCategory.set("parent", Parse.User.current());

      newUserCategory.save({ 

        success: function (){
          console.log ('userCategory successfully created!');
          response.success('userCategory successfully created!');
        },

        error: function (){
          console.log('error!!!');
        response.error('Request failed');
        }

      });
});

I assume the issue is that the UITextFields are sending the numbers in a format my cloud code doesn't like. In addition to this error, I would like to set it so that only numbers are allowed when inputting a value in this field.

How can I programmatically create these two fields in a way that will send the data in a format thats compatible with the cloud code, and that only allows numbers?

One of your properties — it looks like itemCondition — is apparently nil. This may be because your properties are weak, so the variable is getting nulled out before you get a chance to look at it, or it may be because your selected segment isn't one of the values you're testing for and thus the variable is nnever set. I can't understand why those string properties are weak, and I strongly suspect they shouldn't be.