iPhone application accessing data values from different classes

Question

I have 4 classes i.e views in my application. Class A, having variable a and b.

After clicking on button which is on view A of class A it leads to class B, which is table view controller. Then class B leads to class C. then class C leads to class D.

Now i want to access values of a and b of class A into class D. I tried it with NSNotification but not succeeded.

Please suggest.

I tried with NSNotification:

i tried with NSNotification like Class A---

-(IBAction) selectButton:(id) sender{



NSString * a = [NSString stringWithFormat:@"Manjinder singh"];
NSDictionary * dict = [NSDictionary dictionaryWithObject:a forKey:@"1"];
[[NSNotificationCenter defaultCenter] postNotificationName:@"sendMessage" object:self userInfo:dict];

}  

Then Class D----

- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil

{
self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
if (self) {
    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(sendMessage:) name:@"sendMessage" object:nil];
}
return self;
}




-(void)sendMessage:(NSNotification *)notification{


A *dil=[[A alloc] init];
nslog(@"dil.a");




NSLog(@"USERINFO:MyUserInfo (its a dictionary):%@",[[notification userInfo] valueForKey:@"1"]);

}

This is the rendom try but basically i want to show variable a and b of class A into class D.

Update:------------ MyCoolViewController.h// a class where data send from

@protocol MyCoolViewDelegate;

@interface MyCoolViewController : UIViewController  {


id <MyCoolViewDelegate> delegate;//
}
@property (nonatomic, assign) id delegate;//


@end
@protocol MyCoolViewDelegate <NSObject>//

-(void)sendAStringToAnotherView:(NSString*)string;
@end

MyCoolViewController.m

-(void)viewDidLoad{

[delegate sendAStringToAnotherView:@"this is a string"];
}




firstViewController.m  //a class where data sent
-(void)viewDidLoad{

MyCoolViewController *myViewControllerPointer=[[MyCoolViewController alloc] init];
myViewControllerPointer.delegate = self;//
}

-(void)sendAStringToAnotherView:(NSString*)string
{
//displays the string as console output
NSLog(@"plzzzzzz show data",string);
}

value of string is not passed to this class because it is not showing in NSLog output. UPDATED 2---

MyCoolViewController.m

#import “MyCoolViewController.h”
#import "firstViewController.h"


@implementation MyCoolViewController
@synthesize label1,sttr; 



@synthesize delegate;//







-(IBAction) selectButton:(id) sender{



if (curri==nil) {

     curri=[[CurrancyViewController alloc] initWithNibName:nil bundle:nil];



    [self.navigationController pushViewController:curri animated:YES];
}

      curri=nil;

  //CHECK ThIS  [curri release];
}






- (void)viewDidLoad
{
[delegate sendAStringToAnotherView:@"this is a string"];






self.view.backgroundColor = [UIColor colorWithPatternImage:[UIImage imageNamed:@"background1.png"]];




[super viewDidLoad];

}

- (BOOL)shouldAutorotateToInterfaceOrientation:  (UIInterfaceOrientation)interfaceOrientation
{
// Return YES for supported orientations
return (interfaceOrientation == UIInterfaceOrientationPortrait);
 }

@end

Answer 1

Can you give more context about what specifically you are trying to achieve? It sounds like you want to pass data between several UIViewControllers. Here is how to set up a delegate for one of your view controllers:

#import <UIKit/UIKit.h>

@protocol MyCoolViewControllerDelegate;
@interface MyCoolViewController : UIViewController {
    id <MyCoolViewControllerDelegate> delegate;
}

@property (nonatomic, assign) id delegate;

@end

@protocol MyCoolViewControllerDelegate <NSObject>

-(void)sendAStringToAnotherView:(NSString*)string;

@end

Then you will should synthesize the delegate

@synthesize delegate;

and then when you want to pass data to, lets say a parent view, call this function:

[delegate sendAStringToAnotherView:@"this is a string"];

In the other view controller, wherever you instantiated the instance of this UIViewController, you need to set that self as the delegate;

myViewControllerPointer.delegate = self;

and then implement the delegate function in the parent view controller.

 -(void)sendAStringToAnotherView:(NSString*)string
{
   //displays the string as console output
   NSLog(string);
}

The fact that you need communicate between views like this could possibly mean that there is a more efficient means of structuring your app. Can't say for sure without more info.

Try and use this template to add a delegate to your own app.

Answer 2

You could use delegation here

D would become the delegate of A, and when you click the button, A sends a message to D with the variables as arguments and D responds by performing a method.