setObjectForKey: exception: object cannot be nil

Question

I am building an app using Parse and Xcode. When using the Parse PFTableView I am getting the error:

Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '*** setObjectForKey: object cannot be nil (key: classname)'

I understand that I am not setting the key somewhere in my code, but I do not know where and how to fix it.

#import "TableViewController.h"
#import <Parse/Parse.h>

@interface TableViewController ()

@end

@implementation TableViewController

- (id)initWithStyle:(UITableViewStyle)style
{
    self = [super initWithStyle:style];
    if (self) {
        // This table displays items in the Todo class
        self.parseClassName = @"Todo";
        self.pullToRefreshEnabled = YES;
        self.paginationEnabled = YES;
        self.objectsPerPage = 25;
    }
    return self;
}


- (void)viewDidLoad
{
    [super viewDidLoad];

    // Uncomment the following line to preserve selection between presentations.
    // self.clearsSelectionOnViewWillAppear = NO;

    // Uncomment the following line to display an Edit button in the navigation bar for this view controller.
    // self.navigationItem.rightBarButtonItem = self.editButtonItem;

    self.parentViewController.view.backgroundColor = [UIColor colorWithPatternImage:[UIImage imageNamed:@"red_bokeh.png"]];
    self.tableView.backgroundColor = [UIColor clearColor];

}

- (void)viewDidUnload
{
    [super viewDidUnload];
    // Release any retained subviews of the main view.
    // e.g. self.myOutlet = nil;
}

- (void)viewWillAppear:(BOOL)animated
{
    [super viewWillAppear:animated];
}

- (void)viewDidAppear:(BOOL)animated
{
    [super viewDidAppear:animated];
}

- (void)viewWillDisappear:(BOOL)animated
{
    [super viewWillDisappear:animated];
}

- (void)viewDidDisappear:(BOOL)animated
{
    [super viewDidDisappear:animated];
}

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

#pragma mark - Table view data source

#pragma mark - Parse

- (void)objectsDidLoad:(NSError *)error {
    [super objectsDidLoad:error];

    // This method is called every time objects are loaded from Parse via the PFQuery
}

- (void)objectsWillLoad {
    [super objectsWillLoad];

    // This method is called before a PFQuery is fired to get more objects
}

- (PFQuery *)queryForTable {
    PFQuery *query = [PFQuery queryWithClassName:self.parseClassName];

    // If no objects are loaded in memory, we look to the cache first to fill the table
    // and then subsequently do a query against the network.
    if (self.objects.count == 0) {
        query.cachePolicy = kPFCachePolicyCacheThenNetwork;
    }

    [query orderByDescending:@"createdAt"];

    return query;
}


- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath object:(PFObject *)object
{
    static NSString *CellIdentifier = @"Cell";

    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
    if (cell == nil) {
        cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleSubtitle reuseIdentifier:CellIdentifier];
    }

    // Configure the cell
    cell.textLabel.text = object[@"text"];
    cell.detailTextLabel.text = [NSString stringWithFormat:@"Priority: %@",
                                 object[@"priority"]];

    return cell;
}
- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath
{
    [super tableView:tableView didSelectRowAtIndexPath:indexPath];
}


@end

Here is the TableViewController.h:

#import <UIKit/UIKit.h>

@interface TableViewController : PFQueryTableViewController

@end

Answer 1

I solved this issue by following this Parse.com/help

I just change the method from initWithStyle to initWithCoder.

- (id)initWithCoder:(NSCoder *)aDecoder
    {
    self = [super initWithCoder:aDecoder];
    if (self) {

        // The className to query on
        self.parseClassName = kPAPPhotoClassKey;

        // Whether the built-in pull-to-refresh is enabled
        self.pullToRefreshEnabled = YES;

        // Whether the built-in pagination is enabled
        self.paginationEnabled = YES;

        // The number of objects to show per page
        self.objectsPerPage = 10;

    }
    return self;
}

Answer 2

The variable self.parseclassname is never being set. If I had to guess, you are probably calling -init on the tableView instead of -initWithStyle

To fix it, in a super-temporary, dirty way, you should change this function in the following way:

- (PFQuery *)queryForTable {
    if (!self.parseClassName) {
        self.parseClassName = @"Todo";
    }
    PFQuery *query = [PFQuery queryWithClassName:self.parseClassName];

    // If no objects are loaded in memory, we look to the cache first to fill the table
    // and then subsequently do a query against the network.
    if (self.objects.count == 0) {
        query.cachePolicy = kPFCachePolicyCacheThenNetwork;
    }

    [query orderByDescending:@"createdAt"];

    return query;
}