How do you access a uitableview inside a uinavigationcontroller inside a uitabbarcontroller from app delegate? - objective-c

Question

Im trying to access a refresh control method in a uitableview which is inside a navigationcontroller from a tabbarcontroller which is my root, but im having trouble getting an exact handle.
This is my code so far in the AppDelegate but it doesn't work...
UITableViewController *tableView = (UITableViewController *)[[self.tabbarController viewControllers][0] tableView];
[tableView.refreshControl beginRefreshing];
I have 5 tab bar items which I believe I can access via [0],[1],[2],[3]
And my code in the UITableView (though probably doesnt matter)...
// Add Refresh Control
UIRefreshControl *refreshControl = [[UIRefreshControl alloc] init];
[refreshControl addTarget:appDelegate action:#selector(forceDownload) forControlEvents:UIControlEventValueChanged];
self.refreshControl = refreshControl;
[refreshControl release];
Any help would be greatly appreciated as i cant find any online that access as deep as this.

Answer 1

If you need communication between objects that are unrelated, i think that the best option is to use NSNotifications. This allows you to use the singleton object[NSNotificationCenter defaultCenter], to pass notifications from one object to another (or many others).
So you can put the AppDelegate object (or other object) to observe a specific notification and then post the notification with the tableviewController when you need to refresh the control.
In app delegate class you can add the observer like:
[[NSNotificationCenter defaultCenter] addObserver:self
selector:#selector(forceDownload)
name:#"ForceDownloadNotification"
object:nil];
And, in the tableviewController you can post de notification like:
[[NSNotificationCenter defaultCenter] postNotificationName:#"ForceDownloadNotification"
object:self];
Here, I used the name "ForceDownloadNotification" as the name for the notification. You can use the name that you want, but in order this solution work properly, you must use the same name when you start the observation and when you post the notification.
Here you have a tutorial about this subject.

Answer 2

I like Luis Espinoza's approach but that doesn't answer the question per se.
If you want to call a method inside your UITableViewController nested inside a UINavigationController which is the rootViewController for your App Delegate. First we create a navigationController with the UITableViewController (or a subclass):
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
self.window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]];
// Override point for customization after application launch.
CustomTableViewController *nuTableVC = [[CustomTableViewController alloc] initWithStyle:UITableViewStylePlain];
UINavigationController *nuNavController = [[UINavigationController alloc] initWithRootViewController:nuTableVC];
self.window.rootViewController = nuNavController;
[self.window makeKeyAndVisible];
return YES;
}
Then in your UITableViewController (or subclass) you setup the refreshcontrol just like you asked:
- (void)viewDidLoad {
[super viewDidLoad];
// Add Refresh Control
UIRefreshControl *refreshControl = [[UIRefreshControl alloc] init];
[refreshControl addTarget:[[UIApplication sharedApplication] delegate]
action:#selector(forceDownload)
forControlEvents:UIControlEventValueChanged];
self.refreshControl = refreshControl;
}
Finally to access the UItableViewController you must check if the instances are really the classes that you want, here is my implementation for the method you created (forceDownload) in your App Delegate:
- (void)forceDownload {
NSLog(#"force download method in App Delegate");
UINavigationController *someNavController = (UINavigationController*)[_window rootViewController];
UIViewController *vcInNavController = [[someNavController viewControllers] objectAtIndex:0];
if ([vcInNavController isKindOfClass:[CustomTableViewController class]]) {
NSLog(#"it is my custom Table VC");
NSLog(#"here we can stop the refresh control, or whatever we want");
CustomTableViewController *customTableVC = (CustomTableViewController *)vcInNavController;
[customTableVC.refreshControl performSelector:#selector(endRefreshing)
withObject:nil
afterDelay:1.0f];
}
}
I personally prefer using NSNotificationCenter because is simpler, but that doesn't mean we can't access the objects the way you originally planed.
(if you want the example code just ask for it).
Regards.

Answer 3

If your goal is truely to just keep your refresh control synch'd with the networkActivityIndicator then one option is KVO.
In the viewController's viewDidAppear: add something like this
- (void)viewDidAppear:(BOOL)animated
{
[super viewDidAppear:animated];
UIApplication *application = [UIApplication sharedApplication];
[application addObserver:self
forKeyPath:#"networkActivityIndicatorVisible"
options:NSKeyValueObservingOptionNew
context:myContext];
self.refreshControl.refreshing = [application isNetworkActivityIndicatorVisible];
}
Then make sure to remove this observer when the viewController doesn't need it - perhaps in viewDidDisappear:
- (void)viewWillDisappear:(BOOL)animated
{
[super viewDidDisappear:animated];
[[UIApplication sharedApplication] removeObserver:self
forKeyPath:#"networkActivityIndicatorVisible"
context:myContext];
}
Now for the actual work
- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context;
{
if (myContext == context) {
self.refreshControl.refreshing = [change[NSKeyValueChangeNewKey] boolValue];
} else {
[super observeValueForKeyPath:keyPath ofObject:object change:change context:context];
}
}