I am creating a delegate view controller and presenting it to the user to perform an action but I would like to change a NSString on the delegate view controller based on the originating view controller. For example if the delegate view controller is a delegate of viewControllerA, then display Foo, but if its a delegate of viewControllerB then display Blah. ALthough I cant figure out how to pass some sort of information that indicates what the originating view controller is. I noticed that if i do an NSLog(#"I'm from %#",[self delegate]); it will tell me what the originating view controller is, as well as the memory address, but I cant seem to translate that into an NSString object to examine its value. If theres a way to make that work, or a better way to do this then that works too...
- (IBAction)editDate {
DatePickerViewController *datePickerView = [[DatePickerViewController alloc] init];
datePickerView.delegate = self;
datePickerView.modalTransitionStyle = UIModalTransitionStyleFlipHorizontal;
[self presentModalViewController:datePickerView animated:YES];
[datePickerView release];
}
It seems like you're using some terminology in ways that are different from what most Objective-C coders would mean.
Here you're instantiating a view controller to show as a modal view. That view controller has a property called delegate that allows it to call some methods to report changes to its state. That doesn't make it a "delegate view controller", that makes it "an object with a delegate".
You happen to be using another view controller class as the delegate, but any object that implements the methods that DatePickerViewController objects want to call to report changes could be assigned to that delegate property.
I think that the question you're asking is "how do I make the DatePickerViewController display different information depending on what kind of object it's reporting to?", and the answer is much the same as "how do I make a UILabel show different text depending on the view controller that created it?"—you set properties or call methods on in when you create it.
If you really just want to pass a string to DatePickerViewController, you could add an NSString* property to DatePickerViewController and set it with arbitrary text, with
datePickerView.myString = #"some information that you want";
You could use the class of the delegate.
if([[self delegate] isKindOfClass:[ViewControllerA class]]) {
[self doViewControllerAThings];
}
else {
...
}
Related
I have programmed in several other languages but this is basically my first ios app and I am struggling to correctly implement a UITableView.
After reading the documentation, the most common way to accomplish this is to create a class that is a subclass of UITableViewController. I have done this and I have implemented all data source protocol methods as well as the row selection method from the delegate protocol and gave it three properties.
The first one is the number of rows in the tableview,
the second is an array of the items to be displayed as labels in the table view,
and finally there is a property to hold the text of the label from the selected row.
Once the row is selected, I set the property of that holds this label and then I remove the table form the view with [self.view removeFromSuperView].
The above isn't the only view in my app. The app is a color picker assignment, from school, so the main view contains all of the controls to manipulate the displayed color.
What I did after subclassing UITableViewController was, create an instance of this subclass in my main view controller and made it a property. So, on the main view is a recall button that allows the user to choose from a list of previously saved colors. When this button is clicked the this IBAction method is called
-(IBAction)swithToSavedColorsView:(id)sender {
self.savedColorTable.numberOfRows = self.dictionaryOfSavedColors.count;
NSLog( #"Count in switch view is %d", self.dictionaryOfSavedColors.count );
[ self.view addSubview:self.savedColorTable.view ];
}
This presents a list of the available saved colors and I respond to the row selection with
- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:
(NSIndexPath *)indexPath {
self.textFromColorSelection = [ [ NSString alloc ] init ];
UITableViewCell *cell = [ tableView cellForRowAtIndexPath:indexPath ];
self.textFromColorSelection = cell.textLabel.text;
NSLog(#"The value of selection is %# ", self.textFromColorSelection );
[ self.view removeFromSuperview ]; // Go back to main screen.
}
As I was writing this code I was getting an erie feeling that I went about the creation of the UITableView in the completely wrong way from the beginning. Please let me know if I am doing something wrong as far as how I have communication between these objects set up.
The problem I am actually trying to solve is in the above method after i call
[ self.view removeFromSuperView ], how will my other view know when this has happened? What I want to do when the UITableView closes is have my other view get the label property from the instance I created and use that label to retrieve information out of a database.
Thanks for the help, it is greatly appreciated.
If you need several controllers to respond to the dismissal of the table, you will likely want to use NSNotificationCenter in viewWillDisappear or viewDidDisappear. More likely you are presenting from a viewController and only that viewController is waiting to learn what color was selected. I would suggest handling that with a delegate/protocol pattern.
Add something like this to your color pick table myColorPickTableController.h file above the #interface line:
#class myColorPickTableController;
#protocol myColorPickTableControllerDelegate
-(void)myColorPickTableControllerDidSelectColor:(UIColor *)selectedColor sender:(myColorPickTableController *)sender;
#end
Add a property in that header as well, to store reference to the delegate (the controller which is waiting to hear what color was picked).
#property(nonatomic, unsafe_unretained)id<myColorPickTableControllerDelegate> delegate;
Now, replace the line
[ self.view removeFromSuperview ]; // Go back to main screen.
with
[delegate myColorPickTableControllerDidSelectColor:[UIColor whateverColorWasPicked] sender:self]; // Tell main screen user picked a color
Now in the presenting controller, you need to conform to the protocol by adding to your interface line
#interface myPresentingController : UIWhateverControllerIAm <myColorPickTableDelegate> // Add that part between <>
Now, in myPresentingController.m you implement the method
-(void)myColorPickTableControllerDidSelectColor:(UIColor *)selectedColor sender:(myColorPickTableController *)sender
{
[self saveTheSelectedColor:selectedColor];
[sender.view removeFromSuperview]; // I am not so sure about that, should be presenting, maybe modally or use navigation controller. Should work thought, not my first choice.
sender = nil; // Just for good measure
}
Lastly, remember to make your presenting controller the delegate of the myColorPickTableController when you create it. Set delegate as self like so
myColorPickTableController *pickTable = [myColorPickTableController alloc] init];
pickTable.delegate = self.
In your subclassed UITableViewController, viewWillDisappear and viewDidDisappear should be called after your view is removed. Try sending a notification when your view disappears (look into NSNotificationCenter).
I have a UINavigationController in which I am loading different view controllers. I want to know how can i access the elements (like labels etc) of my previous view.
Here is an eg.
View A
myLabel.text = #"first view";
(User moves to view B)
View B
(user entered a message, that i need to display in View A)
something like ViewA.myLabel.text = #"user entered message"
I tried many things but was not able to find anything very useful. Please help..
I am using Xcode 4 without ARC and without storyboard.
Thanks
Sam
Edited:
I want to update the property declared in viewController of View A and not the labels directly. My labels get updated using that property. Like while pushing the viewController we can pass the values as below.
ViewA *myView = [[ViewA alloc] init];
myView.title = #"View B" ;
myView.tableView.tag = 3;
myView.myTextView.text = #"Some Text";
[self.navigationController pushViewController:myView animated:YES];
[myView release];
Is there any way to pass these values to properties of ViewController of ViewA while popping ViewB and returning back to ViewA ?
The actual scenario is as follows: the user gets and option to write a message in textView or he can use the predefined templates. If he clicks on the templates button he is taken to a list of predefined templates where he can select any of the predefined message. Now I want that when the user click on any of the predefined message the view containing the list of predefined message gets popped of and the message he selected gets automatically populated in the textView of main view. what is the best approach to achieve this ?
TIA
Sam
You should set your AViewController as the delegate of your BViewController so you can message it back after a particular event. Using a delegate will also allow better decoupling of your ViewControllers.
In your BViewController, define a protocol like this :
BViewController.h :
#protocol BViewControllerDelegate <NSObject>
- (void)viewB:(UIViewController *)didEnterMessage:(NSString *)message;
#end
and add a delegate property :
#property (nonatomic, weak) id <BViewControllerDelegate> delegate;
When the user enter the message in your BViewController and hit the button that pops the BViewController to show to AViewController do this :
- (IBAction)messageEntered {
if ([self.delegate respondsToSelector:#selector(viewB:didEnterMessage:)]) {
[self.delegate viewB:self didEnterMessage:self.yourTextField.text];
}
}
Your AViewController should implement the BViewControllerDelegate protocol like this :
AViewController.h :
#interface AViewController <BViewControllerDelegate>
When your AViewController creates the BViewController, it should set itself as its delegate before presenting it. Might look like this :
BViewController *bvc = [[BViewController alloc] init…];
bvc.delegate = self;
And finally, your AViewController should implement the viewB:didEnterMessage: method :
- (void)viewB:(UIViewController *)didEnterMessage:(NSString *)message {
self.myLabel.text = message;
}
That's the cleanest way to do that, IMHO.
You can get the navigation controller's viewControllers property and use it, perhaps like this:
UILabel *label = ((SomeViewController *)[self.navigationController.viewControllers objectAtIndex:1]).myLabel;
However, that is not reliable. Since the “previous” view is off the screen, the system can unload it to free up memory. Then label will be nil.
You could force that other view controller to reload its view (if it has been unloaded) by accessing the view controller's view property.
But really this smells like bad design. You should almost never try to access the views of a view controller when that view controller's view is not on screen. Remember how the system can unload a view controller's view if the view is off-screen? If some UILabel under that view contained the only copy of important data, that data is now gone!
Any important data needs to be stored somewhere other than a view - perhaps in a property of the view controller, or in a model object. You should ask the view controller for the data, or for the model object that contains the data. A view controller's view objects should almost always be considered a private implementation detail of the view controller, not exposed to other classes.
EDIT
Your question is puzzling because you talk about popping ViewB and returning to ViewA, but your code only creates and pushes a ViewA. ViewB is not mentioned in the code.
I will assume that your ViewA creates and pushes a ViewB. So you should give ViewB a property of type ViewA, like this:
#class ViewA; // forward declaration to avoid circular imports
#interface ViewB
#property (weak, nonatomic) ViewA *aView;
Then, when your ViewA creates a ViewB instance, you set the aView property:
#implementation ViewA
- (void)pushViewB {
ViewB *bView = [[ViewB alloc] init];
bView.aView = self;
[self.navigationController pushViewController:bView animated:YES];
}
Now your ViewB has access to the ViewA that created it, and can set the properties of that ViewA.
If you want to write a good code you should follow the Model-View-Controller pattern. Here's rather good tutrial http://www.cocoalab.com/?q=node/24 In a couple of words it means that you should not store data in View (and also a view should not act as controller). I suggest you to write a custom class that will do this management(store data and pass it from one view to another).
If it's just a test app then you can use viewControllers property of UINavigationController to access the controllers which are in navigation stack or just create a variable to store this data for example, in View B
- (void)textFieldDidEndEditing:(UITextField *)textField {
stringToDisplayInFirstController = textField.text;
NSArray * arrayOfControllers = self.navigationController.viewControllers;
UIViewController * viewControllerA = [arrayOfControllers objectAtIndex:[arrayOfControllers count]-1];
viewControllerA.label.text = stringToDisplayInFirstController;
}
I have this in one view:
-(void)viewWillDisappear:(BOOL)animated
{
RootViewController *rVC = [[RootViewController alloc] initWithNibName:#"RootViewController" bundle:nil];
[rVC setMessage:[label text]];
NSLog(#"ihere - %#",rVC.message);
}
The NSLog returns the correct string. How would I reload the data in the RootViewController to update the string message there?
doing this doesn't work in my RootViewController (which i go back to in navcontroller):
-(void)viewWillAppear
{ [[self message] reloadData]; }
because the message is just a string. Can somebody show me how to fix this please?
Hi can someone else try to help me please?
In the viewWillAppear event, i need to reloadData on a NSString. So i need to convert it somehow to an object before i can use reloadData on it.
That's because NSString doesn't have a reloadData method.
And as it is immutable it wouldn't make sense if it did.
What you probably want to do is display your string in viewWillAppear and change the model property in the controller where it gets this from.
Delegation is the usual way to do this and I've written a couple of examples that might help you see what is happening;
DelegationExample
TableViewDelegation
Presuming you're using a NavigationController: Consult your navigation controller's stack (property navigationController in your current controller) to access the element for your root view controller (this would generally be the zeroth element -- use viewControllers). Set your message property using that pointer. Then be sure that your root view controller, in viewWillAppear, uses the property you just set to reset the text of the label of interest (using a simple assignment statement -- self.myLabel.text = self.message;.
I have been trying to add/implement this example to my existing Split View app tests.
Apple Example
I what to use the concept of replacing the detail view or right view, otherwise my app will be different. It is this difference that is causing my problems.
I have a rootviewcontroller or left view and upon choosing something here a new view is pushed onto this view. Upon choosing something in this "pushed view" I want to change the detail view or right hand view. This is the difference to apples example where the rootview does not have a pushed view on it and thus references are not broken.
Below is my change code - the new View DVCases is being initialized but the didload is not happening.
The issues are learner issues to do with my classes.
This below code is in my RootViewController implementation code but my reference to splitviewcontroller is not working if there is a new view pushed.
Second self.navigationcontroller is not correct because I have pushed a second view to the rootviewcontroller.
To centralize and simplify the code what I have done is from the delegate of the pushed view in the didselect event i call a method found in the rootviewcontroller passing the index as a parameter. The code for my custom method contains what is below.
So my question is how do I do this in my situation where I have pushed other views onto the rootview or left side. It appears that after pushing a view the reference to splitviewcontroller is gone and self.navigationcontroller is also gone/or wrong.
UIViewController <SubstitutableDetailViewController> *detailViewController = nil;
if (value == 0) {
DVCases *newDetailViewController = [[DVCases alloc] initWithNibName:#"DVCases" bundle:nil];
detailViewController = newDetailViewController;
}
// Update the split view controller's view controllers array.
NSArray *viewControllers = [[NSArray alloc] initWithObjects:self.navigationController, detailViewController, nil];
splitViewController.viewControllers = viewControllers;
[viewControllers release];
// Dismiss the popover if it's present.
if (popoverController != nil) {
[popoverController dismissPopoverAnimated:YES];
}
// Configure the new view controller's popover button (after the view has been displayed and its toolbar/navigation bar has been created).
if (rootPopoverButtonItem != nil) {
[detailViewController showRootPopoverButtonItem:self.rootPopoverButtonItem];
}
[detailViewController release];
I would appreciate any tips or help you might have.
Initialization of any viewcontroller class does not mean that it will make call to viewDidLoad method.
viewDidLoad method will only be called when you load view of that viewController. Generally we do it either by following methods.
1. Pushing it on navigation stack.
2. Presenting it using modal transition.
3. Adding it on some other view using [someView addSubView:controller.view];
4. Selecting any tabBar item for the first time Or tapping tabBar Item twice.
there may be some other scenarios.
But right now in your code I don't see any of this element.
Initialization means you are calling the direct method for intialization(calling its constructor) like here in above code initWithNibName will call this method of DVClass not any other(until this method had call for other methods inside it).
Thanks
As I am learning to properly code - my problems centres around that.
The above code is perfect as long as you call it using the same instance. I was not. Thus it was not working.
In the end I made my RootViewController a delegate for a method that has the above code. Thus when in another view - this view can call this method and the proper or real instance of RootViewController will implement it.
I have a button inside the content of a UIPopoverController. This button runs a method called myAction.
MyAction has the form
- (void) myAction:(id)sender
so, myAction receives the id of the caller button.
Now, inside this method I would like to dismiss the UIPopoverController, but the only thing I have is the ID of the caller button. Remember that the button is inside the UIPopoverController.
Is there a way to discover the ID of the UIPopoverController, given the button ID I already have?
thanks.
Unfortunately no. At least, not within the standard practices. You might be able to travel up the responder stack to find it, but it's a hack, it's buggy, and it's really, really messy.
If you want to dismiss a popover by pushing a button, some place relevant should keep a reference to the popover. Usually that would be the owner of the popover (not the controller showed within the popover). When the button is pressed, it can send a message to the owner controller, which can then dismiss the popover.
You might be tempted to have the controller displayed inside of the popover be the owner of its own popover, but coding this way is brittle, can get messy (again), and may result in retain loops so that neither ever gets released.
You can access the presenting popoverController by accessing "popoverController" with KVC.
[[self valueForKey:#"popoverController"] dismissPopoverAnimated:YES]
I have this working, and I do not think it is a hack. I have a standard split view iPad app. I then added a method on my detail controller (the owner of the pop over) to handle the dismissal.
On the standard split view architechture, both the root and detail view controllers are available via the app delegate. So I bound a button click inside the pop over to call a method which gets the app delegate. From there I call the method on the detail controller to dismiss the pop over.
This is the code for the method on the View Controller that is displayed inside the popover:
- (void) exitView: (id)sender {
MyAppDelegate *appDelegate = (MyAppDelegate *)[[UIApplication sharedApplication] delegate];
[appDelegate.detailViewController exitDrill];
}
Then the simple method to dismiss on the Detail View Controller:
- (void) exitDrill {
if(dtController != nil){
[dtController dismissPopoverAnimated: YES];
[dtController release];
}
}
I like the ability to do this because it give me a way to show a user how they can exit a pop over. This may not be necessary in future versions of the app; for right now, while this paradigm is still new to the platform, I prefer to let the users gexit a display in a couple fo different ways to make sure I minimize frustration.
As Ed Marty already wrote
If you want to dismiss a popover by pushing a button, some place relevant should keep a reference to the popover
This is very true; however, when showing a UIPopoverController, the class opening the popovercontroller keeps this resource already. So, what you could do is to use this class as the delegate class for your Popover Controller.
To do so, you could do the following, which I use in my code.
In the class opening the popover, this is my code:
- (void)showInformationForView:(Booking*)booking frame:(CGRect)rect
{
BookingDetailsViewController *bookingView = [[BookingDetailsViewController alloc] initWithStyle:UITableViewStyleGrouped booking:booking];
[bookingView setDelegate:self];
UINavigationController *navController = [[UINavigationController alloc] initWithRootViewController:bookingView];
self.popController = [[UIPopoverController alloc] initWithContentViewController:navController];
[self.popController setDelegate:self];
[self.popController setPopoverContentSize:CGSizeMake(320, 320)];
rect.size.width = 0;
[self.popController presentPopoverFromRect:rect inView:self.view permittedArrowDirections:UIPopoverArrowDirectionLeft animated:YES];
}
- (void)dismissPopoverAnimated:(BOOL)animated
{
[self.popController dismissPopoverAnimated:animated];
}
So what I am doing here is creating a UINavigationController and setting a BookingDetailsViewController as its rootViewController. Then I am also adding the current class as delegate to this BookingDetailsViewController.
The second thing I added is a dismissal method called dismissPopoverAnimated:animated.
In my BookingDetailsViewController.h I added the following code:
[...]
#property (nonatomic, strong) id delegate;
[...]
And in my BookingDetailsViewController.m I added this code:
[...]
#synthesize delegate = _delegate;
- (void)viewDidLoad
{
UIBarButtonItem *closeButton = [[UIBarButtonItem alloc] initWithTitle:#"Close" style:UIBarButtonItemStylePlain target:self action:#selector(closeView)];
[self.navigationItem setRightBarButtonItem:closeButton];
[super viewDidLoad];
}
- (void)closeView
{
if ([self.delegate respondsToSelector:#selector(dismissPopoverAnimated:)]) {
[self.delegate dismissPopoverAnimated:YES];
}
else {
NSLog(#"Cannot close the view, nu such dismiss method");
}
}
[...]
What happens is that when the "Close" button in the UINavigationController is pressed, the method closeView is called. This method check if the delegate responds to dismissPopoverAnimated:animated and if so, it calls it. If it does not respond to this method it will show a log message and do nothing more (so it wont crash).
I have written my code using ARC, hence there is no memory management.
I hope this helped you.