iPhone NavigationController Application

Question

I am following the tutorial here to use a UINavigationController to switch between ViewControllers. If I download the code and follow the tutorial it works all fine and dandy, but when I try to apply this to different apps I encounter the following confusion/issue. When I am in the "FirstViewController" how do I access [self navigationController] if I do not have any navigationController in my viewController class? In this example, I cannot find out how or where the navigationController comes from in the FirstViewController. Can someone please explain how this works?

**Note: The full source code for the entire project can be found on the page I linked to above as well.

This is the line that confuses me:

[[self navigationController] pushViewController:secondViewController   animated:YES];

This is the entire code for the viewController:

.h

#import <UIKit/UIKit.h>
@class SecondViewController;

@interface FirstViewController : UIViewController {

    IBOutlet SecondViewController *secondViewController;
}

@property(nonatomic, retain) SecondViewController *secondViewController;

- (IBAction)PressMe:(id)sender;

@end

.m

#import "FirstViewController.h"
#import "SecondViewController.h"


@implementation FirstViewController

@synthesize secondViewController;

- (void)viewDidLoad {
    [super viewDidLoad];
    self.title = @"First View";
}

- (IBAction)PressMe:(id)sender
{
    [[self navigationController] pushViewController:secondViewController animated:YES]; //This line
}


- (void)dealloc {
    [super dealloc];
}


@end

beyerss · Accepted Answer · 2012-08-07 20:07:48Z

1

From Apple's Documentation:

If the receiver or one of its ancestors is a child of a navigation controller, this property contains the owning navigation controller. This property is nil if the view controller is not embedded inside a navigation controller.

So you don't have to declare the navigation controller. If the current view controller was loaded onto a navigation controller then the line you are referencing will provide you with the current navigation controller

answered Aug 7, 2012 at 20:07

beyerss

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1 Comment

MrHappy19 Over a year ago

How do I check to see if the view controller was loaded on the navigation controller? What I did was go into the interface builder and edit the "view controller (root view controller)" on my navigation controller and set its "nib" to my "FirstViewController". But it says that "navigationController is not declared" on that line.

Gabrail · Accepted Answer · 2012-08-07 20:35:26Z

0

simply , you don't have any navigation controller, so you can't switch from view to another one with this

[[self navigationController] pushViewController:secondViewController   animated:YES];

create navigation controller object in your FirstView and use it to move between views and in your PressMe method :

SecondViewController *secondView = [[secondView alloc] initWithNibName:@"SecondViewController" bundle:nil];
        [self.navigationController pushViewController:secondView animated:YES];
[secondView release];

answered Aug 7, 2012 at 20:35

Gabrail

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Comments

Rickye · Accepted Answer · 2012-08-07 20:51:13Z

0

If you are using IB (as you write in the code) right click the button, drag it to the SecondViewController and then select "Touch Up Inside"

answered Aug 7, 2012 at 20:51

Rickye

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