Pass data through view controller, tab bar control

问题:

This is probably something really simple to achieve, but I am new to programming for iOS and I seem to be stuck.

So, basically, I have a tabbed application. I decided that I wanted a navigation bar, in addition to the tab bar. To do this, I put the tab bar controller and then I added my view controllers and embedded in a navigation controller for each view controller, which is then connected to the tab bar.

My hierarchy in the storyboard looks somewhat like this:

1. View Controller
   2. Tab Bar Controller
      3. Navigation Controller
         4. View Controller
      4. Navigation Controller
         4. View Controller

The part where I am stuck here, is when attempting to pass data from the first View Controller and to any of the other View Controllers. Before adding in the navigation controllers, I was using the prepareForSegue method to pass the data, like so:

- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender
{
    if ([[segue identifier] isEqualToString:@"logged"])
    {
        UITabBarController *tabar=segue.destinationViewController;
        SecondViewController *svc=[tabar.viewControllers objectAtIndex:1];
        svc.groupArray = [(NSArray*)sender objectAtIndex:0];
        svc.userArray = [(NSArray*)sender objectAtIndex:1];
        svc.taskArray = [(NSMutableArray*)sender objectAtIndex:2];
        svc.selfArray = [(NSMutableArray*)sender objectAtIndex:3];
        [tabar setSelectedIndex:1];
    }
}

As you can see, I was passing the data to my second view controller and set the tab bar index to 1 using the performSegueWithIdentifier method, since I wanted the second page to open. All of this was working just fine, until I introduced the Navigation Controllers to my code, since I want navigation bars. That's when everything pretty much broke. If I try to run the code as is, the application crashes with the following output in the console:

[UINavigationController setGroupArray:]: unrecognized selector sent to instance 0x7ffa6acec620

*** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[UINavigationController setGroupArray:]: unrecognized selector sent to instance 0x7ffa6acec620'

I've tried messing around with the code a bit, but nothing seems to work really. I am just very confused, and maybe a hint in the right direction would help me out a bit.

回答1:

Since you embedded your view controllers inside navigation controllers they are no longer direct children of the tabbar; however, you are casting the children of the tabbar controller as something other than Navigation controllers. You want to first get the navigation controller, which is a child of the tabbar controller, and then get the child of that navigation controller. This will be your view controller. Then you can set the data for that.

- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender
{
    if ([[segue identifier] isEqualToString:@"logged"])
   {
       UITabBarController *tabar=segue.destinationViewController;
       UINavigationController *navController = [tabbar.viewControllers objectAtIndex:1];
       SecondViewController *svc=[navController.viewControllers objectAtIndex:0];
       svc.groupArray = [(NSArray*)sender objectAtIndex:0];
       svc.userArray = [(NSArray*)sender objectAtIndex:1];
       svc.taskArray = [(NSMutableArray*)sender objectAtIndex:2];
       svc.selfArray = [(NSMutableArray*)sender objectAtIndex:3];
       [tabar setSelectedIndex:1];
   }
}

回答2:

- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender
{
    if ([[segue identifier] isEqualToString:@"logged"])
    {
        UITabBarController *tabar=segue.destinationViewController;
        UINavigationController *navc =[tabar.viewControllers objectAtIndex:1]; 
        SecondViewController *svc=[nvc.viewControllers objectAtIndex:0];
        svc.groupArray = [(NSArray*)sender objectAtIndex:0];
        svc.userArray = [(NSArray*)sender objectAtIndex:1];
        svc.taskArray = [(NSMutableArray*)sender objectAtIndex:2];
        svc.selfArray = [(NSMutableArray*)sender objectAtIndex:3];
        [tabar setSelectedIndex:1];
    }
}

As you have changed UITabbarController root with UINavigationController, hence while fetching viewcontrollers from UITabbarController it will be of navigation controller type.

Then you have to fetch SecondViewController from navigation controller.