Passing Values Between Viewcontrollers Based on List Selection in Swift

Passing values between ViewControllers based on list selection in Swift

If you have an outlet to your tableView in your ViewController, you can just call indexPathForSelectedRow in prepareForSegue.

If your ViewController is a subclass of UITableViewController, then you can do:

    let row = self.tableView.indexPathForSelectedRow().row
    println("row \(row) was selected")

If your ViewController is not a subclass of UITableViewController, set up an IBOutlet to the UITableView in your view controller:

@IBOutlet var tableView: UITableView!

and wire that up in Interface Builder and call it from prepareForSegue as show above.

Passing Data between View Controllers in Swift

Let's assumed we stand at the firstView go to the DetailView and want passing data from firstView to Detailview. To do that with storyboard, at the firstView we will have a method:

override func prepareForSegue(segue: UIStoryboardSegue!, sender: AnyObject!) {
    if (segue.identifier == "segueTest") {
      //Checking identifier is crucial as there might be multiple
      // segues attached to same view
      var detailVC = segue!.destinationViewController as DetailViewController;
      detailVC.toPass = textField.text
    }
}

and then into the class of DetailView we declared a variable:

var toPass: String!

then you can use the variable toPass (of course you can change the type of the variable as you want, in this EX I just demo for string type).

Passing data between view controllers

This question seems to be very popular here on Stack Overflow so I thought I would try and give a better answer to help out people starting in the world of iOS like me.

Passing Data Forward

Passing data forward to a view controller from another view controller. You would use this method if you wanted to pass an object/value from one view controller to another view controller that you may be pushing on to a navigation stack.

For this example, we will have ViewControllerA and ViewControllerB

To pass a BOOL value from ViewControllerA to ViewControllerB we would do the following.

in ViewControllerB.h create a property for the BOOL

 @property (nonatomic, assign) BOOL isSomethingEnabled;

in ViewControllerA you need to tell it about ViewControllerB so use an
```
 #import "ViewControllerB.h"
```

Then where you want to load the view, for example, didSelectRowAtIndex or some IBAction, you need to set the property in ViewControllerB before you push it onto the navigation stack.

    ViewControllerB *viewControllerB = [[ViewControllerB alloc] initWithNib:@"ViewControllerB" bundle:nil];
    viewControllerB.isSomethingEnabled = YES;
    [self pushViewController:viewControllerB animated:YES];

This will set isSomethingEnabled in ViewControllerB to BOOL value YES.

Passing Data Forward using Segues

If you are using Storyboards you are most likely using segues and will need this procedure to pass data forward. This is similar to the above but instead of passing the data before you push the view controller, you use a method called

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

So to pass a BOOL from ViewControllerA to ViewControllerB we would do the following:

in ViewControllerB.h create a property for the BOOL

 @property (nonatomic, assign) BOOL isSomethingEnabled;

in ViewControllerA you need to tell it about ViewControllerB, so use an
```
 #import "ViewControllerB.h"
```
Create the segue from ViewControllerA to ViewControllerB on the storyboard and give it an identifier. In this example we'll call it "showDetailSegue"

Next, we need to add the method to ViewControllerA that is called when any segue is performed. Because of this we need to detect which segue was called and then do something. In our example, we will check for "showDetailSegue" and if that's performed, we will pass our BOOL value to ViewControllerB

 -(void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender{
     if([segue.identifier isEqualToString:@"showDetailSegue"]){
         ViewControllerB *controller = (ViewControllerB *)segue.destinationViewController;
         controller.isSomethingEnabled = YES;
     }
 }

If you have your views embedded in a navigation controller, you need to change the method above slightly to the following

    -(void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender{
        if([segue.identifier isEqualToString:@"showDetailSegue"]){
            UINavigationController *navController = (UINavigationController *)segue.destinationViewController;
            ViewControllerB *controller = (ViewControllerB *)navController.topViewController;
            controller.isSomethingEnabled = YES;
        }
    }

This will set isSomethingEnabled in ViewControllerB to BOOL value YES.

Passing Data Back

To pass data back from ViewControllerB to ViewControllerA you need to use Protocols and Delegates or Blocks, the latter can be used as a loosely coupled mechanism for callbacks.

To do this we will make ViewControllerA a delegate of ViewControllerB. This allows ViewControllerB to send a message back to ViewControllerA enabling us to send data back.

For ViewControllerA to be a delegate of ViewControllerB it must conform to ViewControllerB's protocol which we have to specify. This tells ViewControllerA which methods it must implement.

In ViewControllerB.h, below the #import, but above @interface you specify the protocol.

 @class ViewControllerB;

 @protocol ViewControllerBDelegate <NSObject>
 - (void)addItemViewController:(ViewControllerB *)controller didFinishEnteringItem:(NSString *)item;
 @end

Next still in the ViewControllerB.h, you need to set up a delegate property and synthesize in ViewControllerB.m
```
 @property (nonatomic, weak) id <ViewControllerBDelegate> delegate;
```

In ViewControllerB we call a message on the delegate when we pop the view controller.

 NSString *itemToPassBack = @"Pass this value back to ViewControllerA";
 [self.delegate addItemViewController:self didFinishEnteringItem:itemToPassBack];

That's it for ViewControllerB. Now in ViewControllerA.h, tell ViewControllerA to import ViewControllerB and conform to its protocol.
```
 #import "ViewControllerB.h"

 @interface ViewControllerA : UIViewController <ViewControllerBDelegate>
```

In ViewControllerA.m implement the following method from our protocol

 - (void)addItemViewController:(ViewControllerB *)controller didFinishEnteringItem:(NSString *)item
 {
     NSLog(@"This was returned from ViewControllerB %@", item);
 }

Before pushing viewControllerB to navigation stack we need to tell ViewControllerB that ViewControllerA is its delegate, otherwise we will get an error.

 ViewControllerB *viewControllerB = [[ViewControllerB alloc] initWithNib:@"ViewControllerB" bundle:nil];
 viewControllerB.delegate = self
 [[self navigationController] pushViewController:viewControllerB animated:YES];

References

Using Delegation to Communicate With Other View Controllers in the View Controller Programming Guide
Delegate Pattern

NSNotification center

It's another way to pass data.

// Add an observer in controller(s) where you want to receive data
[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(handleDeepLinking:) name:@"handleDeepLinking" object:nil];

-(void) handleDeepLinking:(NSNotification *) notification {
    id someObject = notification.object // Some custom object that was passed with notification fire.
}

// Post notification
id someObject;
[NSNotificationCenter.defaultCenter postNotificationName:@"handleDeepLinking" object:someObject];

Passing Data back from one class to another (A class can be any controller, Network/session manager, UIView subclass or any other class)

Blocks are anonymous functions.

This example passes data from Controller B to Controller A

Define a block

@property void(^selectedVoucherBlock)(NSString *); // in ContollerA.h

Add block handler (listener)

Where you need a value (for example, you need your API response in ControllerA or you need ContorllerB data on A)

// In ContollerA.m

- (void)viewDidLoad {
    [super viewDidLoad];
    __unsafe_unretained typeof(self) weakSelf = self;
    self.selectedVoucherBlock = ^(NSString *voucher) {
        weakSelf->someLabel.text = voucher;
    };
}

Go to Controller B

UIStoryboard *storyboard = [UIStoryboard storyboardWithName:@"Main" bundle:nil];
ControllerB *vc = [storyboard instantiateViewControllerWithIdentifier:@"ControllerB"];
vc.sourceVC = self;
    [self.navigationController pushViewController:vc animated:NO];

Fire block

-(void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:
(NSIndexPath *)indexPath {
    NSString *voucher = vouchersArray[indexPath.row];
    if (sourceVC.selectVoucherBlock) {
        sourceVC.selectVoucherBlock(voucher);
    }
    [self.navigationController popToViewController:sourceVC animated:YES];
}

Another Working Example for Blocks

passing data between viewControllers under a tabController in swift, event sequence

You are using:

// this is called when the tab's ViewController is selected (*after* the tab item is selected (tapped))
func tabBarController(_ tabBarController: UITabBarController, didSelect viewController: UIViewController) { ... }

when you want to use:

// this is called *when* the tab item is selected (tapped)
override func tabBar(_ tabBar: UITabBar, didSelect item: UITabBarItem) { ... }

Here is a modification to your example:

import UIKit

class MainViewController: UITabBarController, UITabBarControllerDelegate {

    override func viewDidLoad() {
        super.viewDidLoad()
        delegate = self;
    }

    override func tabBar(_ tabBar: UITabBar, didSelect item: UITabBarItem) {

        let n = self.selectedIndex

        if let tabControllers = viewControllers {

            if let _ = tabControllers[n] as? AViewController {
                // *current* VC is AViewController
                if let vcB = tabControllers[n + 1] as? BViewController {
                    vcB.Y = "some valuable data from A"
                }
            }

            else if let _ = tabControllers[n] as? BViewController {
                // *current* VC is BViewController
                if let vcA = tabControllers[n - 1] as? AViewController {
                    vcA.Y = "some valuable data from B"
                }
            }

        }

    }

}

class AViewController: UIViewController {

    @IBOutlet weak var YTextField: UITextField!

    var Y:String = ""

    override func viewDidLoad() {
        super.viewDidLoad()
    }

    override func viewWillAppear(_ animated: Bool) {
        super.viewWillAppear(animated)
        YTextField.text = Y
    }

}

class BViewController: UIViewController {

    @IBOutlet weak var YTextField: UITextField!

    var Y:String = ""

    override func viewDidLoad() {
        super.viewDidLoad()
    }

    override func viewWillAppear(_ animated: Bool) {
        super.viewWillAppear(animated)
        YTextField.text = Y
    }

}

You'll want to do some additional handling / checking to make sure you're getting to the desired tab. You may want to set a variable inside MainViewController on didSelect item and then set the variable inside the "target" view controller on didSelect viewController.

Passing values from one view controller to another in Swift

Here's a general solution with two assumptions. First, UserId is not a UILabel. Second, you meant to use view which was instantiated in the second line, instead of using secondViewController

override func tableView(tableView: UITableView, didSelectRowAtIndexPath indexPath: NSIndexPath) {
    var view: Dashboard = self.storyboard?.instantiateViewControllerWithIdentifier("Dashboard") as Dashboard
    view.userId = employeesId[indexPath.row]
    self.navigationController?.pushViewController(view, animated: true)
    
}

Here's what Dashboard looks like:

class Dashboard: UIViewController {
    var userId: String!
    @IBOutlet var userIDLabel: UILabel!

    override func viewDidLoad() {
        super.viewDidLoad()

        // Do any additional setup after loading the view.
        userIDLabel.text = UserId
    }

    ...
}

Passing data between view controllers

This question seems to be very popular here on Stack Overflow so I thought I would try and give a better answer to help out people starting in the world of iOS like me.

Passing Data Forward

For this example, we will have ViewControllerA and ViewControllerB

To pass a BOOL value from ViewControllerA to ViewControllerB we would do the following.

in ViewControllerB.h create a property for the BOOL

 @property (nonatomic, assign) BOOL isSomethingEnabled;

in ViewControllerA you need to tell it about ViewControllerB so use an
```
 #import "ViewControllerB.h"
```

Then where you want to load the view, for example, didSelectRowAtIndex or some IBAction, you need to set the property in ViewControllerB before you push it onto the navigation stack.

    ViewControllerB *viewControllerB = [[ViewControllerB alloc] initWithNib:@"ViewControllerB" bundle:nil];
    viewControllerB.isSomethingEnabled = YES;
    [self pushViewController:viewControllerB animated:YES];

This will set isSomethingEnabled in ViewControllerB to BOOL value YES.

Passing Data Forward using Segues

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

So to pass a BOOL from ViewControllerA to ViewControllerB we would do the following:

in ViewControllerB.h create a property for the BOOL

 @property (nonatomic, assign) BOOL isSomethingEnabled;

in ViewControllerA you need to tell it about ViewControllerB, so use an
```
 #import "ViewControllerB.h"
```
Create the segue from ViewControllerA to ViewControllerB on the storyboard and give it an identifier. In this example we'll call it "showDetailSegue"

 -(void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender{
     if([segue.identifier isEqualToString:@"showDetailSegue"]){
         ViewControllerB *controller = (ViewControllerB *)segue.destinationViewController;
         controller.isSomethingEnabled = YES;
     }
 }

If you have your views embedded in a navigation controller, you need to change the method above slightly to the following

    -(void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender{
        if([segue.identifier isEqualToString:@"showDetailSegue"]){
            UINavigationController *navController = (UINavigationController *)segue.destinationViewController;
            ViewControllerB *controller = (ViewControllerB *)navController.topViewController;
            controller.isSomethingEnabled = YES;
        }
    }

This will set isSomethingEnabled in ViewControllerB to BOOL value YES.

Passing Data Back

To pass data back from ViewControllerB to ViewControllerA you need to use Protocols and Delegates or Blocks, the latter can be used as a loosely coupled mechanism for callbacks.

To do this we will make ViewControllerA a delegate of ViewControllerB. This allows ViewControllerB to send a message back to ViewControllerA enabling us to send data back.

For ViewControllerA to be a delegate of ViewControllerB it must conform to ViewControllerB's protocol which we have to specify. This tells ViewControllerA which methods it must implement.

In ViewControllerB.h, below the #import, but above @interface you specify the protocol.

 @class ViewControllerB;

 @protocol ViewControllerBDelegate <NSObject>
 - (void)addItemViewController:(ViewControllerB *)controller didFinishEnteringItem:(NSString *)item;
 @end

Next still in the ViewControllerB.h, you need to set up a delegate property and synthesize in ViewControllerB.m
```
 @property (nonatomic, weak) id <ViewControllerBDelegate> delegate;
```

In ViewControllerB we call a message on the delegate when we pop the view controller.

 NSString *itemToPassBack = @"Pass this value back to ViewControllerA";
 [self.delegate addItemViewController:self didFinishEnteringItem:itemToPassBack];

That's it for ViewControllerB. Now in ViewControllerA.h, tell ViewControllerA to import ViewControllerB and conform to its protocol.
```
 #import "ViewControllerB.h"

 @interface ViewControllerA : UIViewController <ViewControllerBDelegate>
```

In ViewControllerA.m implement the following method from our protocol

 - (void)addItemViewController:(ViewControllerB *)controller didFinishEnteringItem:(NSString *)item
 {
     NSLog(@"This was returned from ViewControllerB %@", item);
 }

Before pushing viewControllerB to navigation stack we need to tell ViewControllerB that ViewControllerA is its delegate, otherwise we will get an error.

 ViewControllerB *viewControllerB = [[ViewControllerB alloc] initWithNib:@"ViewControllerB" bundle:nil];
 viewControllerB.delegate = self
 [[self navigationController] pushViewController:viewControllerB animated:YES];

References

Using Delegation to Communicate With Other View Controllers in the View Controller Programming Guide
Delegate Pattern

NSNotification center

It's another way to pass data.

// Add an observer in controller(s) where you want to receive data
[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(handleDeepLinking:) name:@"handleDeepLinking" object:nil];

-(void) handleDeepLinking:(NSNotification *) notification {
    id someObject = notification.object // Some custom object that was passed with notification fire.
}

// Post notification
id someObject;
[NSNotificationCenter.defaultCenter postNotificationName:@"handleDeepLinking" object:someObject];

Passing Data back from one class to another (A class can be any controller, Network/session manager, UIView subclass or any other class)

Blocks are anonymous functions.

This example passes data from Controller B to Controller A

Define a block

@property void(^selectedVoucherBlock)(NSString *); // in ContollerA.h

Add block handler (listener)

Where you need a value (for example, you need your API response in ControllerA or you need ContorllerB data on A)

// In ContollerA.m

- (void)viewDidLoad {
    [super viewDidLoad];
    __unsafe_unretained typeof(self) weakSelf = self;
    self.selectedVoucherBlock = ^(NSString *voucher) {
        weakSelf->someLabel.text = voucher;
    };
}

Go to Controller B

UIStoryboard *storyboard = [UIStoryboard storyboardWithName:@"Main" bundle:nil];
ControllerB *vc = [storyboard instantiateViewControllerWithIdentifier:@"ControllerB"];
vc.sourceVC = self;
    [self.navigationController pushViewController:vc animated:NO];

Fire block

-(void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:
(NSIndexPath *)indexPath {
    NSString *voucher = vouchersArray[indexPath.row];
    if (sourceVC.selectVoucherBlock) {
        sourceVC.selectVoucherBlock(voucher);
    }
    [self.navigationController popToViewController:sourceVC animated:YES];
}

Another Working Example for Blocks

How pass the value of a selected cell to another ViewController?

add a portfolio variable to your next ViewController

   class scheduledDeleivery: UIViewController{
     var customer:String? //suposing this is customer type

then in
override func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {

    let portfolio = structure[indexPath.row]
    let controller = UIStoryboard(name: "Main", bundle: nil).instantiateViewController(withIdentifier: "scheduledDelivery") as! shcheduledDeleivery
    controller.customer = porfolio.customer //here is the customer you need to pass to next viewcontroller
    print(portfolio.customer)
    controller.navigationItem.title = navTitle
    navigationController?.pushViewController(controller, animated: true)
}

Swift 2.2 : Pass value between view controllers iOS

Add a protocol to your SecurityQuestionViewController with a function that accepts the data you want to pass to the previous viewController as a parameter. In your ForgotPasswordViewController implement that function. Before dismissing the SecurityQuestionViewController call that function on delegate.

How to pass variable reference between viewcontrollers?

Classes are reference types:

Unlike value types, reference types are not copied when they are assigned to a variable or constant, or when they are passed to a function. Rather than a copy, a reference to the same existing instance is used instead.

In the case above I think you would be best setting detailVC.setting to setting and then accessing/modifying the object properties on the object directly instead of passing the value of a class property, Does this help?

See Classes are Reference Types in the documentation

EDIT:

I believe you are using the colorsVC to set a color on the themeVC, so you segue to the colorsVC, select a color and this is returned to the themeVC table cell, correct?

If so there are a couple of ways to achieve this, I think the best way would be to pass the cell's row to the colorsVC so that it can update it as needed.

Passing Values Between Viewcontrollers Based on List Selection in Swift