I want to use appdelegate for applicationDidBecomeActive and I want this function to use method which is placed in viewcontroller. How I am gonna do that?
The only thing that I find is to access from anywhere the appdelegate.
You need to give your applicationDelegate class a reference to the viewController that you want to call the method on. You could do this by creating an instance variable or a property of the applicationDelegate that points to your viewController that you want to be able to call the method on. If you create your viewController in the init method of your appDelegate, or in your applicationDidLoad: method, then you can simply assign this viewController to the instance variable/property that you've created.
You can access the root view controller of your app from within the app delegate through the window property, that is self.window.rootViewController. The view controller that you want to access must be a child of the root view controller or at least accessible through it.
I had the same issue of needing to call a method on my view controller from the app delegate. After some digging and reading this answer I tried to call a method (saveData was the method in question) in my view controller directly from the app delegate and it worked as required.
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {[self.window addSubview:rootViewController_iPad.view];
[self.window makeKeyAndVisible];
return YES;
}
-(void)applicationWillResignActive:(UIApplication *)application {
[rootViewController_iPad saveData];
}
Hope this helps.
Related
In the iPhone SDK, can anyone explain the difference between application DidFinishLaunching in delegate and ViewDidLoad method in ViewControler?
applicationDidFinishLaunching is called by the App Delgate when your application has finished launching. This method is useful for doing setup as soon as possible. Examples of this could include setting up GameCenter, and doing some first launch checking.
viewDidLoad is called by a UIViewController after the view is loaded, usually from the nib. However, in some cases, you may want to do setup before the view is loaded. In that case, use
viewWillLoad is called just before the view is loaded, usually from the nib. For the most part, it will not make much of a difference wether you use viewDidLoad or viewWillLoad. However, some setup may have to be done after the view is loaded and other setup you may want to do before the screen displays anything.
applicationDidFinishLaunching is for initial appwide setup, viewWillLoad is for setup before the view is displayed, and viewDidLoad is for setup right after the view is loaded.
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions gets called when your app is finished launching; and viewDidLoad: gets called when an UIView controlled by UIViewController is loaded.
viewDidLoad is the method that is called once the view has been loaded. It is a place where you can insert code that does initial setup of the view once it has been loaded.
The applicationDidFinishLaunching: method of the NSApplication delegate will be called when the app has finished loading.
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
Method available only in application AppDelegate it calles only ones at the time of app is loaded you can do all the stuff related to your application prelaunch here.
-(void)viewDidLoad: called whenever a view is loaded.
it also call ones when the view is loaded
but it's has own copy for every viewController you can do any stuf related to that controller inside it.
I have a simple iOS application with one UIViewController beneath a UINavigationController. The UIViewController has an IBOutlet for an NSManagedObjectContext.
The AppDelegate has an IBOutlet for the nav controller - but not the view controller. The view controller is automatically instantiated ala the XIB process (as a child of the nav controller).
With this setup, how does one cleanly assign or pass the app delegate's NSManagedObjectContext to the view controller's IBOutlet property. There is a nav controller in the way :) and the app delegate doesn't have a direct property for the UIViewController.
It is a weird problem in that, I want to link a property from one XIB component to another component's property. Most of the XIB work I've done takes a property and points it to an object in the XIB which in turn - gets instantiated ala the normal process but in this case, the context is being created correctly in the app delegate, I just want to pass it on to the view controller when it instantiates it.
You don't need to pass it, just grab it from the app delegate as required:
#import "MyAppDleegate.h"
NSManagedObjectContext* moc = [(MyAppDelegate*)[UIApplication sharedApplication].delegate managedObjectContext];
Apple's docs recommend that you pass references to your managed object context to the classes the require them instead of referencing it from your app delegate.
Here's what the application:didFinishLaunchingWithOptions: looks like in one of my Core Data projects.
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
LocationsViewController *lvc = (LocationsViewController *)self.navigationController.topViewController;
lvc.managedObjectContext = self.managedObjectContext;
assert(lvc.managedObjectContext != nil);
[self.window addSubview:self.navigationController.view];
[self.window makeKeyAndVisible];
return YES;
}
You'll see that I also start with a UINavigationController with a single root view controller.
You've got the right idea, but the problem you're wrestling with seems to be entirely of your own creation. You say that your app delegate has an outlet for the navigation controller, but not for the nav controller's root view controller, because you've set up your nib such that the view controller is created when the nib is loaded. There's nothing wrong with that, but there's also no reason that the app delegate shouldn't have an outlet for that controller. Indeed, the entire reason for outlets is to get references to things that are loaded from a nib.
Add an outlet to your app delegate for your root view controller, and connect it. The app delegate can then give the controller a reference to the managed object context.
With respect to your question about multiple view controllers, I wonder what sort of real-world app might have view controller (A), which needs data, load another view controller (B) which doesn't need any data, followed by a third (C) which again needs data? A realistic example might help, if you have one.
Remember that you don't have to pass the entire managed object context to each successive view controller. You can instead pass just the part of the model that the controller will need to do its work by passing a managed object.
I have one single MainViewController which has of course it's one main UIView. I have this main view comprised of many different subviews.
Some of these subviews have their very own ViewController.
Lets say the MAIN view (whose delegate is primarily MainViewController) has a container which loads another UIView that uses a separate UIViewController- SecondaryViewController as the delegate for most it's actions.
This container view is of course loaded in MainViewController via
MyContainerViewController *myContainerController =
[[MyContainerViewController alloc] ...];
[self addSubView: myContainerController.view];
the controller for myContainerController.view though is MyContainerViewController. How inside this controller do I access MainViewController properties? Specifically I need to access MainViewController's - self.navigationController property to push a new ViewController? :)
Does this make any sense? I assume there's going to be casting of some sort involved since it seems I need to somehow retain a reference to MainViewController inside SecondaryViewController?
It doesn't make sense to push a new ViewController from the SecondaryViewController in the MainViewController.
This screws up the design of the code. A child object will access its parents method to call a method. By other words: bad code.
Make a delegate call from the SecondaryViewController to the MainViewController that it state has changed. Then the MainViewController can decide to do with the call and the SecondaryViewController will not know anything about the implementation of the MainViewController.
So:
Make a protocol in SecondaryViewController.
Let the MainViewController be SecondaryViewController's delegate.
Implement the delegate method in MainViewController which pushes the new ViewController.
Expose the desired sub-view controllers as properties of the view controller that contains them.
Expose your root view controller(s) as properties of your app delegate, and synthesize them also.
When you want to access a different UIViewController, first obtain a reference to your appDelegate:
MyAppDelegate* myAppDelegate = [[UIApplication sharedApplication] delegate];
Then just use your chain of properties to get access to your desired view controller.
SubSubViewController* ssvc = myAppDelegate.rootViewController.subViewController.subSubViewController;
Some folks frown upon the use of the sharedApplication class method to obtain the reference to a delegate, but I've used it in multiple apps and not suffered for it (yet). The alternative is to pipe your appDelegate through your hierarchy of viewControllers.
Can I call the following instance of first view from another second view
(void)applicationDidFinishLaunching:(UIApplication *)application
applicationDidFinishLaunching is called by the application framework when your application launches. You should never be calling it.
It is part of your application's delegate, not of the view.
I am working on a view based application. In this i have two viewcontrollers. They are: Rootviewcontroller and Detailviewcontroller.
Now i am passing a values to Detailviewcontroller using pushViewController method.It works fine. But now when i pop out from this Detailviewcontroller i should access myfunction in Rootviewcontroller. Is it possible please suggest?
Any help would be apprecited !
-Sathiya
call myfunction in the root view controller's viewWillAppear:(BOOL)animated method or the viewDidAppear:(BOOL)animated method, depending on when you want it to be called. that way whenever that controller appears the code you need will be run.
I don't really understand your question 100%, but I think you want to access the methods of the Root ViewController from another View Controller further up the stack?
You can do something like this in DetailViewController:
RootViewController *rootViewController = (RootViewController*)self.navigationController.topViewController;
Now that you have a reference to the Root, you can call methods on it as you wish.
Store instance of rootViewController in AppDelegate.
// AppDelegate.h
RootViewController* rootViewController;
Add an access method to the implementation.
// AppDelegate.m
- (UIViewController*) GetRootViewController {
return rootViewController;
}
Call this method to get the rootViewController from anywhere in your app.
UIViewController* controller =
[(AppDelegate*)[[UIApplication sharedApplication] delegate] GetRootViewController];