Passing data from view controller to tab bar controller in iOS

Question

I'm developing an iOS app and now I'm at a loss. I'm trying to pass data from the first View Controller to the first tab of a TabBarViewController (with using the storyboard). I found a lot of tutorials that explain how to pass data between view controllers, but nothing worked with my tab bar. I know that the tab bar controller contains a kind of array of views. The relation between the View Controller and the Tab Bar Controller is realized using a segue (push). So, I thought it is easy to use the prepareForSegue() - method. Like that:

 - (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender{
 if ([[segue identifier] isEqualToString:@"tab"]) {

 // ...

    } 
 }  

Unfortunately, the relation between the Tab Bar Controller and each tab bar view is no real segue. It's only a "relationship". That means, there is no segue identifier I am able to use for the the method above-mentioned. Is there a possibility to use the prepareForSegue in this case? If not, any ideas how to solve this problem? I know that there is a similar question, but the answer wasn't that helpful. Do I have to create a new file for every tab (view) within the tab bar controller? Or is it possible to have one class (m. & h.) for the whole tab bar controller, accessing the several view with objectAtIndex()?

Thanks in advance!

Answer 1

Here's my setup that worked:

1. Setup Segue:
   1. Setup View Controller with segue to Tab Bar Controller with 2 child View Controllers in Storyboard
   2. Specify segue identifier (tab)
2. Setup Classes in Storyboard:
   1. View Controller class = ViewController
   2. Tab Bar Controller class = TabBarController
   3. Tab Bar Controller Child View Controller class = TabsViewController (shared between both)

3. Setup labelString property in Tab Bar Controller:

   1. In TabBarController.h:

      @property (nonatomic, strong) NSString *labelString;
      

   2. In TabBarController.m:

      @synthesize labelString;
      

4. Setup prepareForSegue method in ViewController.m:

   #import "TabBarController.h"
   
   ...
   
   -(void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender{
       if ([[segue identifier] isEqualToString:@"tab"]){
           TabBarController *tabBar = [segue destinationViewController];
           [tabBar setLabelString:[NSString stringWithFormat:@"This has been set"]];
       }
   }
   

5. Setup UILabels for Child Tab Bar View Controllers.

   1. Drag default UILabel controls into both child View Controllers

   2. Create property in TabsViewController.h:

      @property (nonatomic, strong) IBOutlet UILabel *label;
      

   3. Hook 5.1 and 5.2 up in Storyboard

6. Setup ViewDidLoad method in TabsViewController.m:

   #import "TabBarController.h"
   
   ...
   
   @synthesize label;
   
   ...
   
   - (void)viewDidLoad
   {
       [super viewDidLoad];
   
       TabBarController *tabBar = (TabBarController *)self.tabBarController;
       label.text = [NSString stringWithFormat:@"Tab %i: %@",[tabBar.viewControllers indexOfObject:self],tabBar.labelString];
   }
   

Now clicking on the 1st and 2nd tabs will have the labels display Tab 0: This has been set and Tab 1: This has been set, respectively.