CODEWITHSUNDEEP
iosobjective-cnsnotificationcenternslog
Themis Beris
Themis Beris

Reputation: 990

NSNotificationCenter , prints memory address

I have in my app a UITableview Controller, a View Controller and I'm trying to pass NSDictionary from UITableview Controller to my ViewController, using NSNotificationCenter. So, I push a notification at my UITableview Controller and then I add an observer ,using a selector at my ViewController.The selector is called,but I have an NSLog and get memory results ,like :

ViewController: 0x8a0bcc0

I have tried to pass NSString instead of NSDictionary , but I get again memory results , and not the value of the string.

My code :

UITableView Controller

    NSString *string=@"This is a test string";
    [[NSNotificationCenter defaultCenter] postNotificationName: @"Update" object: string];

ViewController

    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(incomingNotification:) name:@"Update" object:nil];
    [[NSNotificationCenter defaultCenter] postNotificationName:@"Update" object:self];

And here is the incomingNotification selector method:

-(void) incomingNotification : (NSNotification *)notification{
    NSLog(@"Trying to print : %@",[notification object]);
}

All Notifications take place at ViewDidLoad method.Thank you!

UPDATE

Finally , I quit using NSNotificationCenter and used properties to pass data ,changing a bit the inheretence from my TableViewController. No idea why Notifications did not work ,as they were supposed to. Thank you all ,very much for your suggestions and ideas :)

Upvotes: 1

Views: 323

Answers (2)

medvedNick
medvedNick

Reputation: 4510

If I understand correctly, UIViewController is shown after you tap a button on UITableViewController. And you if you are adding a ViewController as observer in its -viewDidLoad:, then it will be able to receive notifications only when it is loaded.

What do you need:

1) override -init or -initWithNibName: method of ViewController like this:

-(id) init
{
    self = [super init];
    if (self)
    {
        [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(incomingNotification:) name:@"Update" object:nil];
    }
    return self;
}

so you can be sure ViewController is observing for notifications from the beginning (well, this might be unnecessary step for your case)

2) when you push ViewController you need to send a notification after it was created, like this:

-(void) tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath
{
    ViewController *nextController = [[ViewController alloc] initWithNibName:nil bundle:nil];
    [self.navigationController pushViewController:nextController animated:YES];

    NSString *string=@"This is a test string";
    [[NSNotificationCenter defaultCenter] postNotificationName: @"Update" object: string];
}

However, if you're trying just to send some parameters from one view controller to another, this is the wrong way. Just create a property in ViewController and in method -tableView:didSelectRowAtIndex: of UITableViewController set this property

Upvotes: 0

Ihar Katkavets
Ihar Katkavets

Reputation: 1570

[[NSNotificationCenter defaultCenter] postNotificationName:@"Update" object:self]

Object means the object that generates a notification. To post parameters use another method

[[NSNotificationCenter defaultCenter] postNotificationName:@"Update" object:self userInfo:string]

Upvotes: 1

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