When calling method from other view controller, it becomes dealloc'd

Question

I have two view controllers. We'll call them listViewController and mapViewController. The listViewController shows first, a user taps a button that shows the mapViewController. The user taps a button on a annotation which is where my problems start.

When the user taps a button on mapViewController, I would like to call a method listViewController and dismiss mapViewController. To do this I am using this code:

mapViewController.m

listViewController* lvc = [[listViewController alloc] initWithNibName:nil bundle:nil];
[lvc getInformation:StringParameter];
[self dismissViewControllerAnimated:YES completion:nil];

However, when executing getInformation it seems that the listViewController class has been dealloc'd because all of the objects that I initialized in the viewDidLoad on listViewController are now nil including self, which just breaks everything.

I assume I'm creating the listViewController object incorrectly in mapViewController. I've tried it with a nil for nibName with the same result.

You need to use a delegate pattern: http://stackoverflow.com/questions/8606674/uimodaltransitionstylepartialcurl-doesnt-get-back-to-previous-state-not-dismi — user523234, Jul 11 '14 at 03:30
Very similar question with several correct answers that will probably solve your issue http://stackoverflow.com/questions/24457936/warning-attempt-to-present-whose-view-is-not-in-the-window-hierarchy/24459150#24459150 — Brandon, Jul 11 '14 at 03:55

score 1 · Accepted Answer · answered Jul 11 '14 at 03:40

1

Ok, Let me clear one thing. On listViewController, you presentViewController a mapViewcontroller right? And you want invoke getInformation of the instance from mapViewController. In the code you're added, you instantiate listViewController again. You have 2 different instance of listViewController.

answered Jul 11 '14 at 03:40

Ryan

4,799
1
29
56

Okay. I think you're right. How do I select the pre-existing instance then? – ecnepsnai Jul 11 '14 at 05:46
Several ways to send message. Such as delegate, notification, block callback. If you need detail about each case, add comment. – Ryan Jul 11 '14 at 08:35
I've used NSNotification before, so I'll try that. Thank you. – ecnepsnai Jul 11 '14 at 18:01

score 1 · Answer 2 · answered Jul 11 '14 at 17:15

One option is to use a delegate pattern:

In your MapViewController.h file:

@protocol MapViewControllerDelegate <NSObject>
-(void)dismissMe;
-(void)getInformation:(NSString *)stringParameter;

@end

@interface MapViewController : UIViewController
@property (weak)id <MapViewControllerDelegate> delegate;
@end

In your MapViewController.m file:

-(void)annotationButtonTap:(id)button
{
    [self.delegate getInformation:stringParameter];
    [self.delegate dismissMe];
}

In your ListViewController.h

#import "MapViewController.h"

@interface ListViewController : UIViewController <MapViewControllerDelegate>

-(void)dismissMe
{
    [self dismissViewControllerAnimated:YES completion:nil];
}

-(void)getInformation:(NSString *)stringParameter
{
    //do whatever you plan with stringParameter
}

And somewhere in you ListViewController.m file where you create the MapViewController instance:

mapViewController = [[MapViewController alloc] initWithNibName:@"MapViewController" bundle:nil];
mapViewController.delegate = self;   //make sure you do this

When calling method from other view controller, it becomes dealloc'd

2 Answers2