How to Pass Values between Multiple View Controllers using Delegate / Protocol

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

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"?

Below is the code of the First VC and Third VC:

#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

#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];
    }
}

Answer 1 · 2015-07-28T21:39:59Z

July 28, 2015 9:39pm

Hi, you need to create a manual seque in the storyboard and create an instance of your view controller via segue.destinationViewController

#import "FirstViewController.h"
//In the third controller user prepareForSegue:sender: method

- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender
{
    FirstViewController *firstVC = (FirstViewController *)segue.destinationViewController;
    firstVC.propertyName = dataYouWantToPass;
}

Answer 2 · 2016-07-20T17:52:35Z

July 20, 2016 5:52pm

(Old question but...) You're using a Singleton and delegation which are two different ways of communicating between VCs (and I stay away from shared instances because they're bad for testing). I think all you need to do is pass the delegate from A, in the prepareForSegue method to B, and then pass it from B to C in B's prepare for segue method. It looks like you're trying to set the third delegate(C) from the first VC(A) by using the shared instance which is wonky. So do this in A and B

- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender
{
    NextViewController *nextVC = (NextViewController *)segue.destinationViewController;
    nextVC.delegate = self; // self for First vc, self.delegate for second VC.
}

Keep passing the delegate that way and use the delegation pattern, where NextViewController will be replaced by which ever type is next, i.e., ThirdVC or SecondVC. Keep away from the singleton.

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Mike Zhu

Mike Zhu

How to Pass Values between Multiple View Controllers using Delegate / Protocol

Mike Zhu

Mike Zhu

2 Answers

Stepan Ulyanin

Stepan Ulyanin

David Rynn

David Rynn