I am inside a class on a view-based app, one that was creating with one view controller.
WHen I am inside the view controller I can access its view using self.view, but how do I access the same view if I am inside a class?
[[UIApplication sharedApplication] delegate]... //??? what do I put here?
thanks
Assuming that the view controller is a member of your application delegate. you can access it like this: ("YourAppDelegate" should be replaced with the actual type name of your application delegate)
( ( YourAppDelegate *) [ [ UIApplication sharedApplication ] delegate ] ).viewController.view;
If you're trying to give a singleton a reference to your main viewController, a better solution might be to get your MyAppDelegate to set a viewController property on your singleton at launch:
- (void)applicationDidFinishLaunching:(UIApplication *)application
{
[MySingletonClass sharedSingleton].viewController = self.viewController;
}
If you plan on re-using a Singleton like this in multiple projects, it often makes more sense to set these sort of properties from your AppDelegate.
A subview really shouldn't be manipulating a parent view, each class should manage it's own view.
Anyway, if your class is a subclass of UIView and is a subview of the viewController, you can get the viewController's view by accessing the superview property to get your parent view.
Related
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.
I have a RootViewController class and a UserSettingsController class. I have defined the UITableView methods (numberOfRowsInSection, cellForRowAtIndexPath) in the RootViewController class.
I want to reload the table view defined in the RootViewController class from the UserSettingsController class. How can I get control of the tableView Object in the RootViewController class from the UserSettingsController class?
I tried the following, but it tries to load a new tableview object.
RootViewController *rootViewController = [[RootViewController alloc]init];
[rootViewController.mytableView reloadData];
[rootViewController autorelease];
You can reload rootViewController.mytableView in viewWillAppear method of RootViewController itself. This will make rootViewController.mytableView reload when you are about to go to the rootViewController view. If the data you want to load is not much (as in takes more time to load like fetching data from the web) you will be fine with this solution.
Otherwise, to load rootViewController.mytableView from you settings view, you can use NSNotification like this:
In RootViewController.m :
//This goes in viewDidLoad
[[NSNotificationCenter defaultCenter] addObserver:self selector:#selector(reloadTableViewData) name:#"ReloadRootViewControllerTable" object:nil];
Then make a method like this:
-(void) reloadTableViewData{
[mytableView reloadData];
}
In Settings view, where you want to reload the RootViewController tableView, write this:
[[NSNotificationCenter defaultCenter] postNotificationName:#"ReloadRootViewControllerTable" object:nil];
This will automatically call the reloadTableViewData method of RootViewController without your need to do subclassing or anything. :)
Make use of notifications with custom name to call static methods in other classes. They are very handy.
I am presuming if what you want to do is to show the same exact table in two different view controllers.
Make myTableView a global or singleton and share it as a property between rootViewController and userSettingsController. Better yet, do a little more work and create a class for your myTableView so you can more easily set it up and manipulate it without having to spread duplicate code in the view controllers' implementation.
In each view controller, test to see if (myTableVIew == nil), and if so, go ahead and initialize and set it up (preferably by going through the tableview class you made). Once set up, you need to make sure you add myTableView to the properties (retained) of both view controllers. Then to display this tableView in each of the controllers, you will just have to do a [self.view addSubview:myTableView]; where self is the view controller that is active at the time.
Yes mahboudz you are absolutely correctly saying that tableview valuw ould be nil
Because if reinitialize the class from another class using init , the objects are reset to nil which are previously set.
And than when you want to reload it it doesn't works because the value of tableview is nil
I didnot get better answer for resolving this please let me know if any buddy knows the solution
Edited for brevity:
How does a subview access properties in its superview and its superview's view controller? Easy enough to go down the chain. How do we go back up?
Original (verbose) post:
The immediate problem I'm trying to solve is simplifying the "birth" of a somewhat complex view. The large picture has to do with Nibs and how subclasses (of UIView in particular) that have beyond trivial initializers are reconstituted when the view loads.
I have some custom UIViews - subviews of a subview of my viewcontroller's view. When I instantiate these views in particular they need a reference to some properties (NSNumberFormatter, & NSDictionary) of the View Controller.
Currenty I use a method to instantiate them:
- (id)initWithFrame:(CGRect)frame items:(NSDictionary *)dictionary forEditingMode:(EditingMode)mode
I'm experimenting with moving them into a Nib to let them reconstitute themselves and running into basic design issues. One being I think I'm limited to initWithFrame as the default initializer?!? If so how can these objects look into the parent view controller and get a reference to the dictionary and some other properties?
Are there methods I could call within initWithFrame (similar to the ones that retrieve the UIApplication delegate) but would instead allow the child view to send methods to it's parent views and/or controllers?
Send in the MVC police, I'm sure I'm breaking something...
It should work the other way round.
The views only contain controls (text fields, etc.). The data lives in a model, and the view/window controllers mediate, accessing and setting the view controls values, synchronizing with the model.
OK, sometimes you may need to have a dictionary shared between the controller and the view. Then create a dictionary property in the view and set it in the awakeFromNib method of the nib owner.
You can set up outlets that get connected to the view's superview or view controller and pull out the info in awakeFromNib. You need to use awakeFromNib instead of init* because the connections won't be created until then.
FYI, if you instantiate via a Nib, your designated initializer is initWithCoder:, not initWithFrame: (but don't use either for this).
You should probably be doing this through the view controller manually just after the nib is loaded. This means that you will have to set the shared dictionary AFTER the view has been initialized. You might do it like so:
#interface MyViewController : UIViewController {
IBOutlet MyView* view1;
IBOutlet MyView* view2;
IBOutlet MyView* view3;
}
#end
#implementation MyViewController
-(void) viewDidLoad;
{
NSDictionary* sharedDict = //make the shared dictionary here;
view1.sharedDict = sharedDict;
view2.sharedDict = sharedDict;
view3.sharedDict = sharedDict;
}
#end
I have an view controller class. I want to do some things in my view when the accelerometer detects movement and calls the accelerometer:didAccelerate: method in the delegate object.
That delegate object is the problem here in my brain. Currently, my brain is freezed and I don't get it what would be better. Let me know what you think!
Solution 1)
In my view controller class I conform to the UIAccelerometerDelegate protocol, and implement that accelerometer:didAccelerate: method.
In the -applicationDidFinishLaunching: method of my AppDelegate class I set that view controller object up as the delegate for receiving method calls upon accelerations. I think that's not really good.
Solution 2)
I create a blank new object called AccelerationDelegate, conform to that UIAccelerometerDelegate protocol, implement that accelerometer:didAccelerate: method and in the -applicationDidFinishLaunching: method of my AppDelegate class I set that view controller object up as the delegate for receiving method calls upon accelerations.
But for solution 2 my brain got stuck a little bit! How would I access the view objects from my view controller inside that object?
The problem here is, that I have more than one view controller around. I use a tab bar controller to switch between them.
Any suggestions how I could get that right?
I agree that the second method is better. Are you looking to access just the currently selected tab view, or just a specific view in your app.
In any case, what I would do is to set up properties for your UITabViewController in your UIApplicationDelegate so that you can access it from the delegate (you can get the app delegate by calling [[UIApplication sharedApplication] delegate]). For example:
YourApplicationDelegate *appDelegate = (YourApplicationDelegate *)[[UIApplication sharedApplication] delegate];
FirstUIViewController *firstViewController = appDelegate.firstViewController;
[firstViewController doStuff];
where firstViewController is a property on your delegate.
If your acceleration is specific to one view controller, then it makes sense to have the view controller receive the information necessary to alter its own subviews. However, it might be better to set your view controller to be the delegate when the view appears, and set the delegate to null when it disappears. (Specifically, - (void) viewWillAppear: and - (void) viewWillDisappear:)