How do I pass data from a tab bar controller to one of its tabs?

Question

I have a UITabBarController set up in storyboard. I want to pass a dictionary of data from the tab bar controller for use in the appropriate child tab, which is a standard UIViewController.

This seems like a long questions to answer, but I really don't know where to start. I'm looking for the easiest way through this. Must I make the tabs function programmatically? Pointing me towards any useful developer documentation would also be much appreciated.

-Austin
p.s. i'm new and have so far depended on storyboard for viewcontroller transitions

Solution 1

It took a couple of days, but I discovered a simple solution. In my TabBarController's viewDidLoad method, I can access and set attributes of my the tabbed subviews using

    [[self viewControllers] objectAtIndex:0]

or whatever index you wish to access.

Saving that as an instance of my tab1_viewController gives me a pointer to the object, from which I can get and set my property values. This was initially unclear because storyboard created the tab_viewController objects for me. I never had a chance to initialize them the way I wanted to!

Solution 2

Your best bet is to use notifications.

In your tab bar, you would do this:

NSDictionary *myDictionary; // Populate this with your data.

// Fire the notification along with your NSDictionary object.
[[NSNotificationCenter defaultCenter] postNotificationName:@"Some_Notification_Name" 
                                                    object:myDictionary];        

Then in your child tab ViewController, you would "listen" for that notification.

[[NSNotificationCenter defaultCenter] addObserver:self 
                                         selector:@selector(handleNotification:) 
                                             name:@"Some_Notification_Name" 
                                           object:nil];

- (void)handleNotification:(id)object {
  // Use your NSDictionary object here.
}

Solution 3

If you got an UINavigationController as one of your UITabBarController view controllers, you can do the following:

NSArray *viewControllers = [self.tabBarController viewControllers];
UINavigationController *myNavController = (UINavigationController *)viewControllers[2];
MyViewController *myController = [[myNavController childViewControllers] firstObject];
// Remember to alloc/init objects first if the objects haven't been initialized already.
[myController.whateverArray = [[NSArray alloc] initWithArray:@[@"Example1", @"Example2"]];
[self.tabBarController setSelectedIndex:2];

Solution 4

With Swift:

if let navController = self.tabBarController?.viewControllers?[1] as? UINavigationController{
        if let testController = navController.childViewControllers.first as? MyViewController{
            testController.data = data
            self.tabBarController?.selectedIndex = 1
        }
}

Solution 5

Using Swift

If you have UINavigationController as one of the tabs in UITabBarController, you want to get the instance of the child view controller instead of creating a new instance and push it to the navigation view controller before changing the tab view index. You can do this...

This sample code assumes the Navigation Controller is at the first tab (index 0) and "childViewController" is embedded in the Navigation Controller.

let viewControllers = self.tabBarController?.viewControllers

let navController = viewControllers![0] as! UINavigationController

let profileViewController = self.storyboard?.instantiateViewControllerWithIdentifier("childViewController") as? ProfileViewController

profileViewController!.parameter1 = "Value1"

profileViewController!.parameter2 = "Value2"

navController.pushViewController(profileViewController!, animated: true)

self.tabBarController?.selectedIndex = 0

View more solutions

Comments

[Jeffery Thomas]

I am having trouble parsing this. How are you storing data in a UITabBarController? Are you subclassing UITabBarController? The tab bar controller is really only a meta controller used to control view controllers. In Apple's MVC framework, view controllers should be used to bind model data to views. If you need to share data between view controllers in a complex way, then you can use notifications, create a singleton, store the data in an app delegate, or use a shared external store like CoreData.

[austin]

Jeff, so be specific, I pass the data to the UITabBarController, however I don't understand how to distribute the data to the separate tabbed view controllers

[austin]

i'm having trouble getting this to work. i've tried putting the tabBarController code in its viewDidLoad and in its tabBarController:didSelectViewController, no success in either. I put the child code in its viewDidLoad

[Blazej SLEBODA]

[self.viewVontrollers firstObject] is more secure.

[DogCoffee]

Couldn't have dreamed of an easier solution. Gold!! This covers the solution about and discusses possible issues with more than 5 tabs. makeapppie.com/2015/02/04/…