Need assistance regarding passing data from child to parent in UINavigationcontroller - ios

Question

In UINavigationController this is child controller
.h
#protocol childProtocol <NSObject>
-(void)childMethod:(NSArray*)params;
#end
#property (strong, nonatomic) id<childProtocol>childDelegate;
#property (weak, nonatomic) parentVC *pVC;
.m
if([self.childDelegate respondsToSelector:#selector(childMethod:)]) {
[self.childDelegate performSelector:#selector(childMethod:) withObject:self.arry];
}
This is my parent controller
.m
-(void)childMethod:(NSArray *)params {
// some work
}
...
childVC *cVC = [[childVC alloc]init];
cVC.pVC = self;
But childMethod: is not getting called so I searched on internet and got this post
UINavigationControllers: How to pass value to higher (parent?) controller in stack?
I tried to create a weak reference but dont know how to use to make delegate pass data from child to parent?

Answer 1

Try this. Check the sample project attached
ParentViewController.h
#import <UIKit/UIKit.h>
#interface ParentViewController : UIViewController
- (void)passData:(NSString *)strText;
#end
ParentViewController.m
- (IBAction)btnGoToSecondView:(id)sender {
ChildViewController *secondVC = [[ChildViewController alloc] initWithNibName:#"ChildViewController" bundle:nil];
secondVC.delegate = self;
[self presentViewController:secondVC animated:YES completion:nil];
}
- (void)passData:(NSString *)strText {
NSLog(#"Data Passed = %#",strText);
}
ChildViewController.h
#import <UIKit/UIKit.h>
#import "ParentViewController.h"
#class ParentViewController;
#interface ChildViewController : UIViewController
#property(nonatomic, assign) ParentViewController *delegate;
#end
ChildViewController.m
- (IBAction)btnPassDataBack:(id)sender {
if([self.delegate respondsToSelector:#selector(passData:)]) {
[self.delegate passData:#"Hello"];
}
[self dismissViewControllerAnimated:YES completion:nil];
}
Sample Project

Answer 2

This is child controller.h
#protocol childProtocol <NSObject>
-(void)childMethod:(NSArray*)params;
#end
#property (strong, nonatomic) id<childProtocol>childDelegate;
#property (weak, nonatomic) parentVC *pVC;
.m
if([self.childDelegate respondsToSelector:#selector(childMethod:)]) {
[self.childDelegate performSelector:#selector(childMethod:) withObject:self.arry];
}
This is my parent controller.h
#import <UIKit/UIKit.h>
#import "ChildController.h"
#interface perentController : UIViewController < childProtocol >
.m
- (void)childMethod:(NSArray *)params {
// some work
}
EDITED :
And Dont Forget to add childViewOBJ.childDelegate = self; at the time of create ChildViewController's object. such like,
childVC *cVC = [[childVC alloc]init];
cVC.childDelegate = self;
cVC.pVC = self;
[self presentModalViewController:cVC animated:YES];
For More information about How to create/use of Protocol.

Answer 3

First of all, you are not checking for the same selector as you declared in your protocol declaration so it won't respond to that. You declared the method childMethod: whereas you are checking if your childDelegate responds to myMethod: selector which does not so it won't go into the if condition.
Also the parent view controller is missing the implementation the method childMethod: in its .m. Implement that in your parent view controller or it will crash because of not finding the exact selector definition.
Since you are using a UINavigationController, the parent view controller won't be lost till the child view controller exist so the childDelegate property must not be strong unless you intend to hold onto your delegate in child view controller for some reason.