Basically the problem I am having is I am unable to call a method in my Main view controller(called Recorder) from another view called Table.
The table view is loaded as a Modalview controller(presentmodalViewController) from Recorder when the user clicks on a button. The table view lets my users change from setting 1 to setting 2 and has a done button (which calls dismissmodalviewcontroller) and returns the user to the main view(Recorder).
What I want is to call a method in Recorder when the done button is clicked on Table View. This method is called Changeview and changes the setting. I am currently unable to call this method properly.
The current code I have is:
changeView method
- (void)changeView
{
[levelsView changeView];
}
TableViewController interface file
RecorderViewController*recorderViewController;
#property (nonatomic, retain) RecorderViewController *recorderViewController;
TableViewController implementation file
#synthesize recorderViewController;
- (void)viewWillDisappear:(BOOL)animated
{
[super viewWillDisappear:animated];
[recorderViewController changeView];
}
Method called when Done button is pressed
- (IBAction) Switch: (id) sender {
[self dismissModalViewControllerAnimated:YES];
}
The current code does not give me any errors but it also does not change the setting. I have also tried to setup notifications with no luck. Any insight into this?
Are you setting the value of recorderViewController when you initialize the tableViewController (i.e., are you setting tableViewController.recorderViewController = self in your Recorder class)? If not, then your call to [recorderViewController changeView] is sending a message to nil – which doesn't crash, but it doesn't do anything either.
As an aside, passing your TableViewController a reference to your RecorderViewController is probably not the best way for two controllers to communicate: You may want to consider using NSNotificationCenter, or passing a model object and using Key-Value Observing.
Related
I have 2 viewcontrollers, with a segue between them. My main viewcontroller is called ViewController. in my second viewcontroller called PreferencesViewController I have a button that has to change some values in my main ViewController. But it doesn't...
I have set up a delegate protocol in my PreferencesViewController.h like I saw on a few examples on Stack Overflow (yes I did google it ;) ).
I also have imported the PreferencesViewController.h file to my main ViewController, aswell I told the viewcontroller to be the delegate: <PreferencesViewControllerDelegate>
I also implemented the method in my implementation of the main ViewController. But this method doesn't get called when I press the button. I implemented [self.delegate methodExample]; in to my IBAction
I've read a lot about setting the delegate. Where do I need to do this? do I need to create and alloc/init a instance of my PreferenceViewController? I tried this and then told the instance instance.delegate = self but that didn't work also...
Hope someone can help me out!
You're correct that you need to set the delegate. The easiest place to do this when using segues is in the source view controller (ViewController, in this case) using he prepareForSegue:sender: method. The segue object passed to this method has a reference to the destination view controller; you probably want to do something like:
- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender {
if ([segue.identifier isEqualToString:#"Your preferences segue identifier"]) {
PreferencesViewController *preferencesViewController =
segue.destinationViewController;
preferencesViewController.delegate = self;
}
}
Since you're using segues, the system is doing the alloc/init of the new view controller for you; this method is called by the system to let you do any hooking up of the new view controller before it's displayed.
Hello everyone — I am a beginner in iPhone programming and Core Data. I am currently trying to learn some of the theory behind Core Data, and have been using this tutorial to help me implement it in my app.
The tutorial teaches by making the main view a UITableViewController that lists the saved objects and another UITableViewController that saves objects (where you enter in the attributes).
The app that I am creating has 3 views. The main view is a plain UIViewController (it handles calculations), you are able to save your calculations by tapping a UIBarButtonItem that brings you to the second view where you enter in more specific attributes. Once you tap save, you are taken BACK to the main view, where you are able to tap a Show Saved button to access the UITableViewController containing saved objects.
I have included #imported the UITableViewController files into my main view's interface file, but when I run the program, I get an error on this line in my prepareForSegue method:
addShoeSizeTVC.managedObjectContext = self.managedObjectContext;
The error is "Property managedObjectContext not found on object of type 'SSFViewController*'" I understand the meaning of this error — I don't have any object called managedObjectContext in my SSFViewController class, but I figured that if I included my file that DOES contain managedObjectContext that it would still be recognized. I should add, that in the tutorial, the prepareForSegue method was contained in the list view for the segue to the add new object UITableViewController. I moved this method to my mainViewController.
I also get an error in my App Delegate in my ApplicationDidFinishLaunchingWithOptions method:
controller.managedObjectContext = self.managedObjectContext;
I understand that this stems from the same problem with the other error (it gives the same error message).
I do not understand how to pass data going from my viewA (mainView), to viewB (add object), back to viewA, then to viewC (view saved objects). I have heard about delegation and am using it in my prepareForSegue method in my SSFViewController main view:
- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender {
if ([segue.identifier isEqualToString:#"Add Object Segue"]) {
NSLog(#"Setting ObjectsTVC as a delegate of AddObjectTVC");
AddObjectTVC *addObjectTVC = segue.destinationViewController;
addObjectTVC.delegate = addObjectTVC.self;
addObjectTVC.managedObjectContext = addObjectTVC.self.managedObjectContext;
}
}
Also on the addObjectTVC.delegate = addObjectTVC.self; line I get a warning that says "Passing 'AddObjectTVC*' to parameter of incompatible type 'id'"
Do I have to set up an NSManagedContext or another delegation method in my main view? Or is it something that I must add to any of my Table views???
Thank you very much. I feel like this is a simple problem to solve, if provided with the right information. I am happy to post any other methods that I used if needed to solve the problem. I am a beginner, so it would be great if you could explain in a beginner-friendly way.
Thanks!
First of all, if you want data from ViewA to ViewB, insert a property in the ViewB and you can pass data from ViewA to this #property
Example
ViewB:
#property (nonatomic, strong) NSString *yourName;
(don't forget to call #synthesize yourName )
ViewA: (in prepareForSegue method)
"ViewB-Controller" *controller = segue.destinationViewController;
controller.yourName = self.name
--> name will be passed to ViewB
Second:
I prefer a delegate which send from ViewB to ViewA "Hey please save your data". It keeps your controller easy and smart, and you don't have to manage the save method from all view controllers. Delegate is an important chapter in iOS and it can be very frustrated for a beginner. (I was in the same situation 9 months before ;))
Search for a delegate example and try to understand how it works (learning by doing), if you have further question about delegate, I will friendly respond to your question.
It isn't the view controller that has the managedObjectContext property, but your UIManagedDocument.
The context is typically described as the 'scratch pad' in which your app will work with the data store.
I have two view controllers (BuildingsViewController and RoomsViewController) that both use a function within the App Delegate called upload. The upload function basically does an HTTP request, and if its successful or unsuccessful, triggers a uialertview. This is working fine.
The part I'm struggling with is from within the app delegate's connectionDidFinishLoading method. I need to be able to basically refresh the current view controller via perhaps viewWillAppear method of that view controller. Inside the viewWillAppear function of each view controller I have code which determines the buttons on the bottom toolbar.
I want the "upload" button in the toolbar of each view controller to automatically be removed when the uploading is done via the app delegate.
I've tried doing [viewController viewWillAppear:YES] from within the connectionDidFinishLoading method of the app delegate, but it never gets called.
I hope I'm clear enough. Any help is greatly appreciated.
Thanks.
To do the refresh of the view do not call viewWillAppear if the view is already displayed. What you want to do is the following:
When ConnectionDidFinishLoading method is triggered post a notification
[[NSNotificationCenter defaultCenter] postNotificationName:#"refreshView" object:nil];
In your viewController observe for this notification. You do it by adding this code to your init or viewDidLoad method
[[NSNotificationCenter defaultCenter] addObserver:self selector:#selector(refreshView:) name:#"refreshView" object:nil];
Now implement -(void)refreshView:(NSNotification *) notification method in your viewController to manage your view to your liking.
If you are targeting iOS 4.0 and later, you can use the window's rootViewController property to get the current view controller.
[window.rootViewController viewWillAppear];
If you want your application to run on versions prior to iOS 4.0, then you could add an instance variable to the application delegate to remember which view controller called the upload method, having the controller send itself as a parameter.
- (void)upload:(UIViewController *)viewController {
self.uploadingViewController = viewController; // This is the property you add
...
}
- (void)connectionDidFinishLoading:(NSURLConnection *)connection {
[self.uploadingViewController viewWillAppear];
self.uploadingViewController = nil;
}
You should also consider using a different method to reload the buttons, something like reloadButtons, since it is not related to the view appearing in this case. You would then call that method from within viewWillAppear.
Step 1:
In your App Delegate .h file you need to declare a protocol like so:
#protocol AppConnectionDelegate <NSObject>
#required
-(void)connectionFinished:(NSObject*)outObject;
#end
In the same file, add an ivar like so:
id *delegate;
Declare the ivar as a property:
#property (nonatomic, assign) id<AppConnectionDelegate> delegate;
In the App Delegate .m file, synthesize the ivar:
#synthesize delegate;
In the App Delegate .m file, on connectionDidFinishLoading do:
if([self.delegate respondsToSelector:#selector(connectionFinished:)])
{
[self.delegate connectionFinished:objectYouWantToSend];
}
In your viewcontroller's .h file, implement the AppConnectionDelegate by importing a reference to the app delegate file:
#import "AppDelegate_iPhone.h" //if using iPhone
#import "AppDelegate_iPad.h" //if using iPad
In the same file, at the end of the first line of the interface declaration do:
#interface AppDelegate_iPhone : AppDelegate_Shared <AppConnectionDelegate>
Declare ivars accordingly:
AppDelegate_iPhone *appDelegate; //if using iPhone
AppDelegate_iPad *appDelegate; // if using iPad
In your viewcontroller's .m file in the viewDidLoad(), get a reference to your app delegate using:
If iPhone;
appDelegate = (AppDelegate_iPhone*)[[UIApplication sharedApplication] delegate];
If iPad:
appDelegate = (AppDelegate_iPad*)[[UIApplication sharedApplication] delegate];
Then set the viewcontroller to be the delegate in viewDidLoad() by doing:
appDelegate.delegate = self;
Now you need to simply implement the connectionFinished method in the .m file:
- (void)connectionFinished:(NSObject*)incomingObject
{
//Do whatever you want here when the connection is finished. IncomingObject is the object that the app delegate sent.
}
Now whenever your app delegate's connectionDidFinishLoading is called, the view controller will be notified.
[It's a best practice to set appDelegate.delegate = nil if you're done using the connectionFinished callback]
This is tried and tested. If you have questions, leave a comment......
--EDIT--This is a robust alternative to NSNotification. I use both depending on the requirements. The process I use to decide between using NSNotification or a delegate callback using a protocol is simply:
For notifications:
One sender, multiple listeners.
No reference possible between sender and listener.
Complex/multiple objects need not be sent
For delegate callbacks using protocols:
One sender, limited (usually 1) listeners.
A reference between sender and listener is possible.
Complex/multiple objects are to be sent (for example, response objects that need to be sent)
I know sending objects is possible through notifications but I prefer protocols for that.
--EDIT--
Worse comes to worst, you can have both view controllers adhere to a simple one method protocol that will remove that button and refresh the view. Then in your connectionDidFinishLoading method, since you know your view controller must adhere to that protocol, by your design, you simply do something like
ViewController<MyProtocol> curView = (Get the current view controller somehow);
[curview refreshView];
I don't really know if what I'm doing is the right way to do it. Right now it seems to be working until it hits a certain point with a EXC_BAD_ACCESS message.
I'll describe what I'm doing as best and with the most relevant details I can tell:
I have a CalendarViewController that inherits UIViewController which is loading from a .xib file (CalendarViewController.xib). The class contains a UIView called contentView which I created and which I initialize with another nib file based on a class which is also inherited from UIViewController:
- (void)viewDidLoad {
[super viewDidLoad];
calendarView = [[CalendarView alloc] initWithNibName:#"CalendarView" bundle:nil];
[contentView addSubview:calendarView.view];
}
(calendarView is the class inheriting UIViewController and viewDidLoad is from CalendarViewController.
CalendarView.xib has a UITableViewController with it's respective UITableView. This Table View Controller is linked to a CalendarTableController to which I also generated a .xib file for it.
Everything is being created just right (apparently) but it is crashing somewhere very unexpected. CalendarTableController also implements a DateLoaderDelegate which loads information from an xml on an external url.
- (void)connectionDidFinishLoading:(NSURLConnection *)connection {
// When the data has all finished loading, we set a copy of the
// loaded data for us to access. This will allow us to not worry about
// whether a load is already in progress when accessing the data.
self.lastLoadedMatchXMLData = [self.matchXMLData copy];
// Make sure the _delegate object actually has the xmlDidFinishLoading
// method, and if it does, call it to notify the delegate that the
// data has finished loading.
if ([_delegate respondsToSelector:#selector(xmlDidFinishLoading)])
{
[_delegate xmlDidFinishLoading];
}
}
The application is getting to this point without any problem. _delegate is containing the correct object (a CalendarTableController which implements the DateLoaderDelegate). But when it arrives to the line:
if ([_delegate respondsToSelector:#selector(xmlDidFinishLoading)])
it crashes with the EXC_BAD_ACCESS, I don't really know the reason, if I look at the debugger, the crash is not occurring in any of my classes as any of them are appearing in the execution stack. URLConnectionClient seems to be generating it, but I don't really know why. The loading of the xml had worked earlier before I rearranged the ViewControllers to work as I have described now.
Any ideas?
It's weird. I fixed the problem but I had to dedicate the whole UIViewController to contain the UITableView. What I did was this:
Create an IBOutlet with the custom UITableViewController (CalendarTableViewController) in the custom UIViewController.
In the loaded .xib file I linked the IBOutlet to a created UITableViewController declared as a CalendarTableViewController.
This way I solved the problem of the UITableViewController being deallocated without reason. But now the image views I had placed in the intermediate UIViewController wouldn't appear. I had to set that UIViewController to contain solely the CalendarTableView and place the image views in the initial UIViewController. Weird, isn't it? I don't like much the hierarchy I created... but for now that will do =S
Check that you have defined properties for all of your subviews and that you are retaining everything that you need to be. Bad Access May mean that you're attempting to call respondsToSelector on an object that has been released.
Have you tried calling loadView before adding the nested controller's view to the parent's view?
Maybe viewDidLoad is not executing before you add the view and some variables were never initialized.
I'm working on a pretty simple multiview app for the iOS and I've been following a great tutorial in an Apress book. I've basically got my rootViewController instantiated and displayed with the app delegate, and I've got a number of content viewControllers (6) which I'd like to swap in and out based on user input. However, in the book they perform their switches with a button on a toolbar placed in the rootView using Interface Builder. It fires a method in rootView that loads up the new content ViewController and displays it.
My problem is that I'd like to perform the content view switch (that lies in my rootViewController instance), but I'd like to trigger the switch action with a button that's in my content view (and is therefore unavailable as my File Owner is my contentViewController, whose reference is held inside my rootViewController).
Hopefully I've explained it well enough, please let me know if I should elaborate more. I appreciate any help!
You need to pass down a reference to your root view controller (RootViewController *rootViewController) when you create your content view either in a custom init method or by just assigning it after you created it: self.contentView.rootViewController = self;.
Now inside your content view you can then call the appropriate method in the root view controller to do the switch: [self.rootViewController switchView]. This call then can be triggered inside the method that is called when you press the button (IBAction method).
So this is what you need to do:
1) Create a property inside the your content view controller of type RootViewController
#class RootViewController;
#interface MyContentViewController : NSObject {
#private
RootViewController *rootViewController;
}
#property (retain) RootViewController *rootViewController;
and make sure it retains the reference.
2) Synthesis the property and add the callback to the root view controller that switches the view:
#implementation MyContentViewController
#synthesize rootViewController;
- (IBAction) switchView:(id) sender {
[rootViewController switchToNextView];
}
-(void) dealloc {
[rootViewController release];
[super dealloc];
}
Also release your retain reference at the end.
3) Assign the root view controller to the content view inside your RootViewController:
self.contentViewController = [[[MyContentViewController alloc]
initWithNibName:#"ContentView"
bundle:nil] autorelease];
self.contentViewController.rootViewController = self;
That should be all. I hope that helps you.
Well, you could simply create an IBAction in each of your child controllers that calls:
[self.parentViewController switchToDifferentController:(int) viewNumber]
and then implement the switchToDifferentController method in your root. Other than ignore the compiler warning that parentView might not implement that method, it might work.
However, that is a bit brittle, as you'd have to assume that it was the parent calling you and that nobody will forget to implement that method.
In general, you use the "delegate" concept for a child controller to ask its parent to do something. The general idea is that you declare a group of methods as a "protocol". Think of it as a contract between objects. One object can say "I promise to implement these methods," and another can then choose to send those messages to it. The contract allows the compiler/system to check for conformance. You'll see this in UITableView, where the OS provides a standard table, but it calls back to your code to provide the individual cells as needed.
To implement a protocol, you mustdo the following: (See code segments below
Declares a protocol for the conversation
Specify that the parent will follows that protocol
Create a delegate property in your child
When the parent is about to launch the child, it assigns itself as the delegate for that child.
When the child wants to switch, it calls the parent using that protocol
#protocol myVCDelegate
- (void)switchToDifferentController:(int) viewNumber ;
#end
#interface ParentViewController : UIViewController <VCDelegate>
#property(nonatomic, assign) id <VCDelegate> delegate
childController.delegate = self;
[self.delegate switchToDifferentController:kController5];