attempt to insert nil object from objects[1]' - ios

Question

I would like to show ChatViewController via a tab bar controller. The current initial view for the app is a NavigationController that loads the ChatViewController. When the ChatViewController is loaded, it checks to see if the ‘joinedchat’ method was called. If not, it presents LoginViewController to allow users to authenticate into the ChatViewController. When the user authenticates, LoginViewController is dismissed.
The LoginViewController and the ComposeViewController, are modal view controllers that are displayed on top of the ChatViewController.
I would like to access this ChatViewController at a much later point in the storyboard, while keeping it as the rootviewcontroller so it can still preserve the data model it uses for classes in anticipation of the $_POST method it uses.
Instead of presenting the LoginViewController if joinedchat hasn’t yet been called, I am showing a different view controller. About 4 view controllers later, after the user has gone on a different process, I use a tab bar controller to access the LoginViewController again. When I try to call the postUpdateRequest method to access the ChatViewController, the app crashes with the output in the debugger:
*** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '*** -[__NSPlaceholderDictionary initWithObjects:forKeys:count:]: attempt to insert nil object from objects[1]'
I suspect it’s because the app uses a strict data model that sets snd stores default versions of the strings that will be posted by the user from LoginViewController via postJoinRequest. Does anyone know any ways to authenticate users using this data?
AppDelegate.m - didRegisterForRemoteNotificationsWithDeviceToken
- (void)application:(UIApplication*)application didRegisterForRemoteNotificationsWithDeviceToken:(NSData*)deviceToken
{
UINavigationController *navigationController = (UINavigationController*)_window.rootViewController;
ChatViewController *chatViewController = (ChatViewController*)[navigationController.viewControllers objectAtIndex:0];
DataModel *dataModel = chatViewController.dataModel;
NSString* oldToken = [dataModel deviceToken];
NSString* newToken = [deviceToken description];
newToken = [newToken stringByTrimmingCharactersInSet:[NSCharacterSet characterSetWithCharactersInString:#"<>"]];
newToken = [newToken stringByReplacingOccurrencesOfString:#" " withString:#""];
NSLog(#"My token is: %#", newToken);
[dataModel setDeviceToken:newToken];
if ([dataModel joinedChat] && ![newToken isEqualToString:oldToken])
{
[self postUpdateRequest];
}
}
AppDelegate.m - PostUpdateRequest
- (void)postUpdateRequest
{
UINavigationController *navigationController = (UINavigationController*)_window.rootViewController;
ChatViewController *chatViewController = (ChatViewController*)[navigationController.viewControllers objectAtIndex:0];
DataModel *dataModel = chatViewController.dataModel;
NSDictionary *params = #{#"cmd":#"update",
#"user_id":[dataModel userId],
#"token":[dataModel deviceToken]};
AFHTTPClient *client = [AFHTTPClient clientWithBaseURL:[NSURL URLWithString:ServerApiURL]];
[client
postPath:#"/api.php"
parameters:params
success:nil failure:nil];
}
DataModel.m - initializer
+ (void)initialize
{
if (self == [DataModel class])
{
// Register default values for our settings
[[NSUserDefaults standardUserDefaults] registerDefaults:
#{NicknameKey: #"",
SecretCodeKey: #"",
JoinedChatKey: #0,
DeviceTokenKey: #"0",
UserId:#""}];
}
}
DataModel.m - userId
- (NSString*)userId
{
NSString *userId = [[NSUserDefaults standardUserDefaults] stringForKey:UserId];
if (userId == nil || userId.length == 0) {
userId = [[[NSUUID UUID] UUIDString] stringByReplacingOccurrencesOfString:#"-" withString:#""];
[[NSUserDefaults standardUserDefaults] setObject:userId forKey:UserId];
}
return userId;
}
LoginViewController.h (Update)
#class DataModel;
// The Login screen lets the user register a nickname and chat room
#interface LoginViewController : UIViewController
#property (nonatomic, assign) DataModel* dataModel;
#property (nonatomic, strong) AFHTTPClient *client;
#end
LoginViewController.m - postJoinRequest & loginAction
- (void)postJoinRequest
{
MBProgressHUD* hud = [MBProgressHUD showHUDAddedTo:self.view animated:YES];
hud.labelText = NSLocalizedString(#"Connecting", nil);
NSDictionary *params = #{#"cmd":#"join",
#"user_id":[_dataModel userId],
#"token":[_dataModel deviceToken],
#"name":[_dataModel nickname],
#"code":[_dataModel secretCode]};
[_client postPath:#"/api.php"
parameters:params
success:^(AFHTTPRequestOperation *operation, id responseObject)
{
if ([self isViewLoaded]) {
[MBProgressHUD hideHUDForView:self.view animated:YES];
if([operation.response statusCode] != 200) {
ShowErrorAlert(NSLocalizedString(#"There was an error communicating with the server", nil));
} else {
[self userDidJoin];
}
}
} failure:^(AFHTTPRequestOperation *operation, NSError *error)
{
if ([self isViewLoaded]) {
[MBProgressHUD hideHUDForView:self.view animated:YES];
ShowErrorAlert([error localizedDescription]);
}
}];
}
- (IBAction)loginAction
{
if (self.nicknameTextField.text.length == 0)
{
ShowErrorAlert(NSLocalizedString(#"Fill in your nickname", nil));
return;
}
if (self.secretCodeTextField.text.length == 0)
{
ShowErrorAlert(NSLocalizedString(#"Fill in a secret code", nil));
return;
}
[self.dataModel setNickname:self.nicknameTextField.text];
[self.dataModel setSecretCode:self.secretCodeTextField.text];
// Hide the keyboard
[self.nicknameTextField resignFirstResponder];
[self.secretCodeTextField resignFirstResponder];
[self postJoinRequest];
}
ChatViewController.h (Update)
#import "ComposeViewController.h"
#class DataModel;
// The main screen of the app. It shows the history of all messages that
// this user has sent and received. It also opens the Compose screen when
// the user wants to send a new message.
#interface ChatViewController : UITableViewController <ComposeDelegate>
#property (nonatomic, strong, readonly) DataModel* dataModel;
#end
Update Terminal Output