passing data value between two view controller using custom protocol - ios

Question

1) I Am passing the value between two view controller using custom
protocol..But the value always showing NULL.
I need to pass the value from second view controller to first view controller
2) In Secondview controller.h
#protocol PopoverTableViewControllerDelegate <NSObject>
#property (nonatomic, strong) id<PopoverTableViewControllerDelegate>myDelegate;
3) secondview controller.m
(void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath
{
NSDictionary*dict=[sercharray objectAtIndex:index];
str=[dict objectForKey:#"id"];
NSLog(#"test value %#",str);
[self.myDelegate didSelectRow:str];
NSLog(#"delegate value %#",self.myDelegate);
//THIS VALUE ALWAYS SHOWING NULL AND ALSO I SHOULD PASS THIS VALUE TO FIRST VIEW
CONTROLLER.I SHOULD USE DISMISS VIEW CONTROLLER.
[self dismissViewControllerAnimated:YES completion:nil];
}
4) First View controller.h
#interface Firstviewcontroller :
UIViewController<PopoverTableViewControllerDelegate>
5) First view controller.m
secondviewcontroller *next=[[seconviewcontroller alloc]init];
next.myDelegate=self;
(void)didSelectRow:(NSString *)cellDataString {
passstring = cellDataString;
NSLog(#"pass string %#",pass string);
//first view controller str variable value i need to pass this string[passstring].
}

Answer 1

I think you might be a little confused about what Delegation is used for and why. For example you might want to make a protocol in a UIViewController subclass if you were doing some kind of action in that ViewController and needed to inform another subclass that that action is being taken, or of the result of that action. Now in order for the subclass that wants to know about the action(the receiver), it has to conform to that protocol in it's header file. You also must "set" the delegate to the receiving class/controller. There are many ways to get a reference to the receiving controller/class to set it as the delegate but a common mistake is allocating and initializing a new instance of that class to set it as the delegate, when that class has already been created.What that does is set your newly created class as the delegate instead of the class that's already been created and waiting for a message. What your trying to do is just pass a value to a Newly created class. Since your just creating this UIViewController class all thats needed for that is a Property in the receiver(ViewControllerTwo). In your case a NSString:
#Property (nonatiomic, retain) NSString *string; //goes in ViewControllerTwo.h
and of course don't forget in the main:
#synthesize string; //Goes in ViewControllerTwo.m
Now there is no need for a setter in your ViewControllerTwo.
- (void)setString:(NSString *)str //This Method can be erased
{ //The setter is created for free
self.myString = str; // when you synthesized the property
}
The setter and Getters are free when you use the #synthesize. Just Pass the value over to the ViewController. The implementation is identical to your code except for the delegate:
ViewControllerTwo *two = [[ViewControllerTwo alloc] initWithNibName:#"ViewControllerTwo" bundle:nil];
[two setString:theString];
[self.navigationController pushViewController:two animated:YES];
[two release];