Ios – Passing Data in Swift Between View Controllers in Same File

iossegueswiftuiviewcontroller

Why can't I pass data from one view controller class to another view controller class when they are in the same .swift file?

I've done both of the tutorials linked bellow in an effort to understand passing data, and both have you make another .swift file for you second view controller. When I followed them exactly it works. When I do everything the same but just put the class SecondViewController in the same .swift file as the class FirstViewController it doesn't work. Why?

I'm building an application with three view controllers and I'd rather just keep all the code in one file if I can. Is this why it's not working or is it just bad form?

Tutorials:

How to Pass Data from View Controller (Swift : Xcode) on YouTube

Segue Between Swift View Controllers on CodingExplorer

This works:

//  ViewController.swift
import UIKit
class ViewController: UIViewController {
    @IBOutlet var TextField: UITextField!    
    override func viewDidLoad() {
        super.viewDidLoad()
    }
    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
    }
    override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
        var DestViewController: ViewTwo = segue.destinationViewController as ViewTwo        
        DestViewController.LabelText = TextField.text        
    }
}

//  ViewTwo.swift
import UIKit
    class ViewTwo: UIViewController {
    @IBOutlet var Label: UILabel!    
    var LabelText = String()    
    override func viewDidLoad() {        
        Label.text = LabelText       
    }
}

This does not:

//  ViewController.swift
import UIKit

class ViewController: UIViewController {
    @IBOutlet var TextField: UITextField!    
    override func viewDidLoad() {
        super.viewDidLoad()
    }
    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
    }
    override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
        var DestViewController: ViewTwo = segue.destinationViewController as ViewTwo        
        DestViewController.LabelText = TextField.text        
    }
}

class ViewTwo: UIViewController {
    @IBOutlet var Label: UILabel!    
    var LabelText = String()    
    override func viewDidLoad() {        
        Label.text = LabelText       
    }
}

Best Answer

Working fine for me.

Have you set the classes for your views properly? The view with your textField (and probably a button to ViewTwo) should be set to ViewController and your second view with the label should be set to ViewTwo.
Check the connections between your label/textField. Are they properly connected to your class?
This is the code I used, which should be exactly the same:

import UIKit

class ViewController: UIViewController {

    @IBOutlet var TextField: UITextField!

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

    override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
        var DestViewController = segue.destinationViewController as! ViewTwo
        DestViewController.LabelText = TextField.text
    }
}

class ViewTwo: UIViewController {

    @IBOutlet var Label: UILabel!

    var LabelText = String()

    override func viewDidLoad() {
        Label.text = LabelText
    }
}

Related Solutions

Ios – 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.

I hope this answer is clear enough for people to understand and that I have not missed anything.

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

Ios – Expand and Collapse tableview cells

If you want the cell to get physically bigger, then where you have your store IndexPath, in heightForRow: use:

override func tableView(tableView: UITableView, heightForRowAtIndexPath indexPath: NSIndexPath) -> CGFloat {
    if selectedIndexPath == indexPath {
      return 230 + extraHeight
    }
    return 230.0
}

Then when you want to expand one in the didSelectRow:

selectedIndexPath = indexPath
tableView.beginUpdates
tableView.endUpdates

Edit

This will make the cells animate themselves getting bigger, you dont need the extra animation blocks in the cell.

Edit 2

 override func tableView(tableView: UITableView, didSelectRowAtIndexPath indexPath: NSIndexPath) {
        if(selectedIndexPath == indexPath) {
          selectedIndexPath = nil

          if let cell = tableView.cellForRowAtIndexPath(indexPath) as? MyTicketsTableViewCell {
            cell.collapse()
          }
          if let cell = tableView.cellForRowAtIndexPath(NSIndexPath(forRow:indexPath.row+1, section: indexPath.section) as? MyTicketsTableViewCell {
            cell.collapse()
          }
        } else {
          selectedIndexPath = indexPath

          if let cell = tableView.cellForRowAtIndexPath(indexPath) as? MyTicketsTableViewCell {
              cell.expand()
          }

          if let cell = tableView.cellForRowAtIndexPath(NSIndexPath(forRow:indexPath.row+1, section: indexPath.section) as? MyTicketsTableViewCell {
             cell.expand()
          }
        }

        tableView.beginUpdates()
        tableView.endUpdates()
    }

Best Answer

Related Solutions

Ios – Passing data between view controllers

References

Ios – Expand and Collapse tableview cells

Related Topic