Coredata helper - ios

Question

So I am creating an app in the form of a social media app. I am using the tutorial found here as a springboard since I am still trying to wrap my brain around Core Data. I've deviated from the tutorial by adding a sign up button that takes the user to a new View Controller and created a .h and a .m file and set the New Member screen to reference the .h and .m files. They are set up as follows for the .h:
#import <UIKit/UIKit.h>
#interface NewMemberViewController : UIViewController
#property (strong, nonatomic) NSManagedObjectContext *managedObjectContext;
#property (strong, nonatomic) IBOutlet UITextField *nameTF;
#property (strong, nonatomic) IBOutlet UITextField *ageTF;
#property (strong, nonatomic) IBOutlet UITextField *usernameTF;
#property (strong, nonatomic) IBOutlet UITextField *passwordTF;
- (IBAction)alreadyMember:(id)sender;
- (IBAction)checkAndLogin:(id)sender;
#end
and for the .m:
#import "NewMemberViewController.h"
#import "CoreDataHelper.h"
#interface NewMemberViewController ()
#end
#implementation NewMemberViewController
#synthesize usernameTF, ageTF, passwordTF, nameTF, managedObjectContext;
- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil
{
self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
if (self) {
// Custom initialization
}
return self;
}
- (void)viewDidLoad
{
[super viewDidLoad];
// Do any additional setup after loading the view.
}
- (void)didReceiveMemoryWarning
{
[super didReceiveMemoryWarning];
// Dispose of any resources that can be recreated.
}
//If the user is already a member simply dismiss the VC
- (IBAction)alreadyMember:(id)sender {
[self dismissViewControllerAnimated:YES completion:nil];
}
//When done editing keyboard
- (IBAction)checkAndLogin:(id)sender {
managedObjectContext =self.managedObjectContext;
//Textfield Reference
UITextField *tf = (UITextField *)sender;
//Check tag numbers If its equal to 1 or 2(nameTF or ageTF) then
if (tf.tag==1||tf.tag==2)
{
[sender resignFirstResponder];
NSLog(#"This is working");
}
//If its equal to 3 then this means the username text field is active
else if (tf.tag == 3)
{
[sender resignFirstResponder];
//do a quick search to see if username is availible
NSPredicate *pred = [NSPredicate predicateWithFormat:#"(username == %#)", [usernameTF text]];
//Run the query to check if user exists
if([CoreDataHelper countForEntity:#"Users" withPredicate:pred andContext:managedObjectContext] > 0)
{
//we found a user
NSLog(#"oh no...");
}
}
}
#end
With that being said if I run my app and go to the signup screen and test to see if the user exists, by typing in admin because it already exists, i get the following error in Xcode:
Canvases[779:11603] * WebKit discarded an uncaught exception in the webView:shouldInsertText:replacingDOMRange:givenAction: delegate: +entityForName: nil is not a legal NSManagedObjectContext parameter searching for entity name 'Users'
What does this mean and why is it being caused?

Answer 1

Have you pass the context to the view controller? Try with:
YourAppDelegate *appDelegate = (YourAppDelegate *)[[UIApplication sharedApplication]delegate];
yourVontext = [appDelegate managedObjectContext];
before fetch.

Answer 2

There is issue with below line.
managedObjectContext = self.managedObjectContext;
self.managedObjectContext is returning nil to managedObjectContext. Instead of self.managedObjectContext you should create Core Data Stack (method implementation)in the Application Delegate and then pass object reference of ManagedObjectContext from AppDelegate to your caller class.