Unable to call delegate method

Question

In my app I've a view controller in which there are a table view, when I tap on one of table view row it should dismiss the actual view controller an pass back an url to load it in a web view. I thought the right way to do that it's to implement a delegate, so I did it but when I try to run the app when I tap on the row of table view it doesn't call the delegate method. I add here some code to understand what's wrong:

HistoryNotificationViewController.h

#import <UIKit/UIKit.h>

@protocol HistoryNotificationDelegate;

@interface HistoryNotificationViewController : UIViewController

@property(nonatomic,weak) id <HistoryNotificationDelegate> delegate;

@end

@protocol HistoryNotificationDelegate <NSObject>

- (void) updateWebViewWithURL:(NSString*)url;

@end

HistoryNotificationViewController.m (I post only the method in which I call the delegate method)

- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath {
    [self.delegate updateWebViewWithURL:[sortedArray[indexPath.row] objectForKey:@"url"]];
    [self dismissViewControllerAnimated:YES completion:nil];
}

HomeViewController.m (view controller that should implement the delegate method of HistoryNotificationViewController.m)

#import "HomeViewController.h"
#import "SSKeychain.h"
#import "SSKeychainQuery.h"
#import "MBProgressHUD.h"
#import "HistoryNotificationViewController.h"

#define SYSTEM_VERSION_LESS_THAN_OR_EQUAL_TO(v)     ([[[UIDevice currentDevice] systemVersion] compare:v options:NSNumericSearch] != NSOrderedDescending)

@interface HomeViewController () <UIWebViewDelegate, HistoryNotificationDelegate>
@property (weak, nonatomic) IBOutlet UIWebView *webView;
- (IBAction)buttonForward:(UIButton *)sender;
- (IBAction)buttonBack:(UIButton *)sender;
@property(nonatomic,strong)MBProgressHUD *hud;

@end

@implementation HomeViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view.
    self.hud = [[MBProgressHUD alloc]init];
    self.hud.labelText = @"Loading";
    self.hud.mode = MBProgressHUDModeIndeterminate;
    [self.view addSubview:self.hud];

    NSURL *url = [[NSURL alloc]init];
    NSURLRequest *request = [[NSURLRequest alloc]init];

    if (!self.website) {
        url = [NSURL URLWithString:[[NSUserDefaults standardUserDefaults] objectForKey:@"website" ]];
        request = [NSURLRequest requestWithURL:url];
    } else {
        [[NSUserDefaults standardUserDefaults] setObject:self.website forKey:@"website"];
        [[NSUserDefaults standardUserDefaults] synchronize];
        url = [NSURL URLWithString:[[NSUserDefaults standardUserDefaults] objectForKey:@"website"]];
        request = [NSURLRequest requestWithURL:url];
    }
    [self.webView loadRequest:request];
}

- (void)didReceiveMemoryWarning {
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}

- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender {
    HistoryNotificationViewController *historyNotificationViewController = [[HistoryNotificationViewController alloc]init];
    [historyNotificationViewController setDelegate:self];   
}

#pragma mark HistoryNotificationDelegate
- (void)updateWebViewWithURL:(NSString *)url {
    NSURLRequest *request = [NSURLRequest requestWithURL:[NSURL URLWithString:url]];
    [self.webView loadRequest:request];
}

#pragma mark UIWebViewDelegate
- (void)webViewDidStartLoad:(UIWebView *)webView {
    [self.hud show:YES];
}

- (void)webViewDidFinishLoad:(UIWebView *)webView {
    [self.hud hide:YES];
}


- (IBAction)buttonForward:(UIButton *)sender {
    [self.webView goForward];
}

- (IBAction)buttonBack:(UIButton *)sender {
    [self.webView goBack];
}
@end

What's wrong in my classes? Why it doesn't execute the delegate method?

Answer 1

Try this,

Make a property for HistoryNotificationViewController by

@property (nonatomic, strong) HistoryNotificationViewController *historyNotificationViewController;

and in prepareForSegue :

- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender {

    UIViewController *destinationVC = [segue destinationViewController];
    if ([destinationVC isKindOfClass:[HistoryNotificationViewController class]]) {

        self.historyNotificationViewController = destinationVC;
        [self.historyNotificationViewController setDelegate:self]; 
    }
}

Answer 2

You need to get HistoryNotificationViewControllers in prepareForSegue from destinationViewController instead of allocating a new object...

#import "HomeViewController.h"
#import "SSKeychain.h"
#import "SSKeychainQuery.h"
#import "MBProgressHUD.h"
#import "HistoryNotificationViewController.h"

#define SYSTEM_VERSION_LESS_THAN_OR_EQUAL_TO(v)     ([[[UIDevice currentDevice] systemVersion] compare:v options:NSNumericSearch] != NSOrderedDescending)

@interface HomeViewController () <UIWebViewDelegate, HistoryNotificationDelegate>{

}
@property (weak, nonatomic) IBOutlet UIWebView *webView;
- (IBAction)buttonForward:(UIButton *)sender;
- (IBAction)buttonBack:(UIButton *)sender;
@property(nonatomic,strong)MBProgressHUD *hud;

@end

@implementation HomeViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view.
    self.hud = [[MBProgressHUD alloc]init];
    self.hud.labelText = @"Loading";
    self.hud.mode = MBProgressHUDModeIndeterminate;
    [self.view addSubview:self.hud];

    NSURL *url = [[NSURL alloc]init];
    NSURLRequest *request = [[NSURLRequest alloc]init];

    if (!self.website) {
        url = [NSURL URLWithString:[[NSUserDefaults standardUserDefaults] objectForKey:@"website" ]];
        request = [NSURLRequest requestWithURL:url];
    } else {
        [[NSUserDefaults standardUserDefaults] setObject:self.website forKey:@"website"];
        [[NSUserDefaults standardUserDefaults] synchronize];
        url = [NSURL URLWithString:[[NSUserDefaults standardUserDefaults] objectForKey:@"website"]];
        request = [NSURLRequest requestWithURL:url];
    }
    [self.webView loadRequest:request];
}

- (void)didReceiveMemoryWarning {
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}

- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender
{
    // Make sure your segue name in storyboard is the same as this line
    if ([[segue identifier] isEqualToString:@"YOUR_SEGUE_NAME_HERE_FOR_HISTORY_NOTIFICATION_VIEWCONTROLLER"])
    {
        // Get reference to the destination view controller
        HistoryNotificationViewController *vc = [segue destinationViewController];

        // Pass any objects to the view controller here, like...
        [vc setDelegate:self];
    }
}


#pragma mark HistoryNotificationDelegate
- (void)updateWebViewWithURL:(NSString *)url {
    NSURLRequest *request = [NSURLRequest requestWithURL:[NSURL URLWithString:url]];
    [self.webView loadRequest:request];
}

#pragma mark UIWebViewDelegate
- (void)webViewDidStartLoad:(UIWebView *)webView {
    [self.hud show:YES];
}

- (void)webViewDidFinishLoad:(UIWebView *)webView {
    [self.hud hide:YES];
}


- (IBAction)buttonForward:(UIButton *)sender {
    [self.webView goForward];
}

- (IBAction)buttonBack:(UIButton *)sender {
    [self.webView goBack];
}

Answer 3

You do not need and should not use delegate at all in this case. Otherwise you're making thing complicated.

Just define a public method in your HomeViewController,

- (void)updateWebViewWithURL:(NSString *)url 
{

}

Same method name as the one you've defined should be ok, but not as a delegate method!

Then, in your HistoryNotificationViewController.m, you'll be able to get a reference of HomeViewController easily. Something like this will do,

NSArray *viewControllers = self.navigationController.viewControllers;
    HomeViewController *homeViewController = [viewControllers objectAtIndex:0];
    [homeViewController updateWebViewWithURL:url];