Delegate not responds to selector - ios

Question

Basically, I am now intend to use delegate to pass values between view controllers.
The flow of the view controllers is A -> B -> C using push segue.
When the user does some action in the "C" view controller, how to pass the value BACK to the first view controller, which is "A"?
In my code, "self.delegate" is always nil and the delegate method is never triggered.
Below is the code of the First VC and Third VC:
First VC .m:
#import "ViewController.h"
#import "ThirdViewController.h"
#interface ViewController ()<PassValueProtocal>
#property (weak, nonatomic) IBOutlet UILabel *myLabel;
#end
#implementation ViewController
{
ThirdViewController *thirdVC;
}
- (void)viewDidLoad {
[super viewDidLoad];
// Do any additional setup after loading the view, typically from a nib.
}
- (void) passValueBack:(NSString *)value
{
NSLog(#"HAHAH");
}
- (void)didReceiveMemoryWarning {
[super didReceiveMemoryWarning];
// Dispose of any resources that can be recreated.
}
- (IBAction)segueToSecondVC:(UIButton *)sender
{
thirdVC = [ThirdViewController sharedManager];
thirdVC.delegate = self;
}
#end
Third VC .h:
#import <UIKit/UIKit.h>
#protocol PassValueProtocal <NSObject>
- (void) passValueBack: (NSString *) value;
#end
#interface ThirdViewController : UIViewController
#property (weak, nonatomic) id<PassValueProtocal>delegate;
+ (id) sharedManager;
#end
Third VC .m:
#import "ThirdViewController.h"
#interface ThirdViewController ()
#property (weak, nonatomic) IBOutlet UITextField *myTextField;
#end
#implementation ThirdViewController
+ (id) sharedManager
{
NSLog(#"myDelegate sharedManager");
static ThirdViewController *sharedManager = nil;
static dispatch_once_t onceToken;
dispatch_once(&onceToken, ^{ sharedManager = [[self alloc] init]; });
return sharedManager;
}
- (void)viewDidLoad {
[super viewDidLoad];
// Do any additional setup after loading the view.
}
- (void)didReceiveMemoryWarning {
[super didReceiveMemoryWarning];
// Dispose of any resources that can be recreated.
}
- (IBAction)passValueAction:(UIButton *)sender
{
NSLog(#"%#", self.delegate);
if ([self.delegate respondsToSelector:#selector(passValueBack:)])
{
[self.delegate passValueBack:self.myTextField.text];
}
}
#end

Answer 1

Your code
- (IBAction)segueToSecondVC:(UIButton *)sender
{
thirdVC = [ThirdViewController sharedManager];
thirdVC.delegate = self;
}
Should not be here. You should implement function prepareForSegue and move this code there. Something like
-(void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender {
ThirdViewController *thirdVC = (ThirdViewController *)segue.destinationViewController;
thirdVC.delegate = self;
}