Passing data between two ViewControllers Problem - iphone

Question

Hi I have two viewControllers.
NewsViewController
#import "SingleViewController.h"
#interface NewsViewController : UIViewController {
}
- (NSString *)getFirstImage:(NSString *)htmlString;
#end
and the implementation file:
#import "SingleViewController.h"
SingleViewController *singleViewController;
#interface NewsPadViewController () <UIActionSheetDelegate>
- (void)loadSubscriptions;
#property (nonatomic, assign) BOOL wrap;
#property (nonatomic, retain) NSMutableArray *items;
#end
#implementation NewsPadViewController
....CODE....
- (void)carouselCurrentItemTapped{
//[self addSubview:articolo];
MWFeedItem *item =[reader.feedItems objectAtIndex:[carousel currentItemIndex]];
NSLog(#"Current Item tappped, index: %d", [carousel currentItemIndex]);
singleViewController.prova.text=#"CIAO";
singleViewController.ciao=#"sample";
[singleViewController.web loadHTMLString:item.summary baseURL:nil];
NSLog(#"conternutio:");
NSLog(singleViewController.ciao);
}
SingleViewController.h
#import <UIKit/UIKit.h>
#interface SingleViewController : UIViewController{
#public
UIWebView *web;
UILabel *prova;
NSString *ciao;
}
#property (nonatomic,retain) IBOutlet UIWebView *web;
#property (nonatomic,retain) IBOutlet UILabel *prova;
#property (nonatomic,retain) IBOutlet NSString *ciao;
#end
and SingleViewController.m
#import "SingleViewController.h"
#implementation SingleViewController
#synthesize web,prova,ciao;
- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil
{
self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
if (self) {
// Custom initialization
}
return self;
}
- (void)didReceiveMemoryWarning
{
// Releases the view if it doesn't have a superview.
[super didReceiveMemoryWarning];
// Release any cached data, images, etc that aren't in use.
}
#pragma mark - View lifecycle
- (void)viewDidLoad
{
[prova setText:ciao];
[super viewDidLoad];
// Do any additional setup after loading the view from its nib.
}
- (void)viewDidUnload
{
[super viewDidUnload];
// Release any retained subviews of the main view.
// e.g. self.myOutlet = nil;
}
- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation
{
// Return YES for supported orientations
return (interfaceOrientation == UIInterfaceOrientationPortrait);
}
#end
Why I can't access from NewsPadViewController at object in SingleViewController? Where is my error? thanks
UPADATE
- (void)carouselCurrentItemTapped{
//[self addSubview:articolo];
MWFeedItem *item =[reader.feedItems objectAtIndex:[carousel currentItemIndex]];
NSLog(#"Current Item tappped, index: %d", [carousel currentItemIndex]);
SingleViewController *singleViewController = [[SingleViewController alloc] initWithNibName:#"SingleViewController" bundle:[NSBundle mainBundle]];
singleViewController.prova.text=#"CIAO";
singleViewController.ciao=#"sample";
[singleViewController.web loadHTMLString:item.summary baseURL:nil];
NSLog(#"conternutio:");
NSLog(singleViewController.ciao);
[singleViewController setOpz:#"sample"];
}

Answer 1

I don't see any instantiation of SingleViewController. You have a pointer to it, but I don't see anywhere in your code example where you actually create it.
Somewhere you need something like:
if (!singleViewController) {
singleViewController = [[SingleViewController alloc] init];
}
or
SingleViewController *singleViewController = [[SingleViewController alloc] initWithNibName:#"SingleView" bundle:nil];
or from somewhere else you need to send a message or set an instance variable in NewsViewController that points to an existing instance of SingleViewController.