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iOS Build a Self-Destructing Message iPhone App Designing and Starting the App A Storyboard with a Tab Bar Controller

Posted by Scott Taylor
Scott Taylor
7,089 Points

Designing and Starting the App - Challenge 2/3

I'm probably being very stupid but where am I going wrong with this code?

Question: The tabs are stored in an array named tabBarItems (line 9). Declare a UITabBarItem variable named tab and set it from tabBarItems using the selectedIndex property.

#import "MainViewController.h"
#import "UITabBarItem.h"

@implementation MainViewController

- (void)viewDidLoad {
    [super viewDidLoad];

    NSArray *tabBarItems = self.tabBarController.tabBar.items;

    // Add your code below! The property for MainViewController's 
    // tab bar controller is named 'tabBarController'.

    [self.tabBarController setSelectedIndex:2];
    UITabBarItem *tab = [tabBarItems objectAtIndex:selectedIndex];

}

@end

8 Answers

Dave Ko
Dave Ko
11,915 Points
Dave Ko
Dave Ko
11,915 Points 
UITabBarItem *tab = tabBarItems [self.tabBarController.selectedIndex];
Stone Preston
Stone Preston
42,016 Points
Stone Preston
Stone Preston
42,016 Points

you are very close. Here is a hint: selectedIndex is a property of the tabBarController, so just using 

[tabBarItems objectAtIndex:selectedIndex];

wont work. you have to chain dot notations together and access the tabBarController THEN the selectedIndex property of that tabBarController

Scott Taylor
Scott Taylor
7,089 Points
Scott Taylor
Scott Taylor
7,089 Points

Stone, thanks for helping me, I really appreciate it. I must be having a blonde moment, as I just can't get it. Any other advice or references you recommend I read? Thanks!

Stone Preston
Stone Preston
42,016 Points
Stone Preston
Stone Preston
42,016 Points

ok, you accessed the tabBarController in the first line you wrote:

[self.tabBarController setSelectedIndex:2];

now you have to access the selectedInexProperty of that same tabBarController using dot notation. Here is a hint: I can access that tabBar property of the tabBarController like so for example:

self.tabBarController.tabBar

you have to access the selectedIndex property of the tabBarController, not the tabBar property.

Scott Taylor
Scott Taylor
7,089 Points
Scott Taylor
Scott Taylor
7,089 Points

Thanks Stone, I got it (eventually!).

Sakina Burch
Sakina Burch
1,853 Points
Sakina Burch
Sakina Burch
1,853 Points

Keep getting this error message There is a compiler error. Please click on preview to view your syntax errors! This is my Code UITabBarItem *tab = [self.selectedIndex.tabBarItems];

Nkem Modu
Nkem Modu
4,511 Points
Nkem Modu
Nkem Modu
4,511 Points

I was having some trouble with this as well, but I finally got it. I'll try to break it down.

You are being asked to create a new UITabBarItem named "tab", and the value of "tab" will equal the value of an object in the "tabBarItems" array.

As we already know, we can access an object in an array if we know the index at which that object is stored:

array_name [index_number];

The array you have to access is "tabBarItems". The index number you want to access is stored within the variable "selectedIndex". However, you can't access "selectedIndex" directly; it is a property of "tabBarController" (and "tabBarController is a property of self).

You know the name of the array.

You know the dot notation that represents the index number.

wenwen liao
wenwen liao
5,736 Points
wenwen liao
wenwen liao
5,736 Points

I have a hard time too, but finally make it! here is my code:

UITabBarItem *tab = tabBarItems[self.tabBarController.selectedIndex];