I have SendingController which push to nav stack SendingDeatilsController (which one has a TableView). User should should pick in TableView one row (it checked by Checkmark) and I would like to pass the value of this row (let it will NSString object) to the SendingController.
How can I realize this behaviour in my application? And is SendingController parent for SendingDetailController (attribute parentController of SDC refers to SC) ??
If you want to implement this behaviour, pass the SendingDetailController a reference to the previous view controller. This way the detail view controller can send a message to the previous one on the stack.
In your SendingDetailController define a weak reference :
// in .h
SendingController *sendingController;
#property(assign) SendingController *sendingController;
// in .m
#synthesize sendingController;
-(void)tableView:(UITableView *)tableView
didSelectRowAtIndexPath:(NSIndexPath *)indexPath {
// retrieve the string and send the message
[sendingController didSelectString:theString];
}
Now before pushing the SendingDetailController on the stack don't forget to set its sendingController property.
// .m
// where you push the vc
if(!sendingDetailController) {
sendingDetailController = [[SendingDetailController alloc]
initWithNibName:#"TheNIBName"
bundle:nil];
sendingDetailController.sendingController = self;
}
[self.navigationController pushViewController:sendingDetailController
animated:YES];
and write the method that will recieve the string.
-(void)didSelectString:(NSString *)aString {
// do anything with string
[self.navigationController popViewControllerAnimated:YES];
}
This should do the job.
For easy asynchronous communication between different UIViewControllers, you may want to look at NSNotification and NSNotificationCenter.
There are plenty tutorials on the web and some good answers here at SO that can show you how to do that exactly.
Related
To start I am building an app to learn the basics of Objective-C. If there is anything unclear please let me know and I will edit my question.
The app is supposed to have the next functionality.
Open the camera preview when the app is executed. On the top there is a button to go to a TemplateController where the user can select an array of frames to select from a UICollectionView. User selects the Template and returns to the Camera Preview. User takes a picture and the picture with the frame selected is shown in the PreviewController. If the user doesn't like the frame and wants to switch it for another one. PreviewController has button on top to go to the TemplateController, select the frame and go back again to the PreviewController with the new frame.
I do not want to create an object for the frame everytime. I want the AppDelegate to hold that object. To keep it alive per say?(sorry, English is not my mother tongue).
I was thinking to use NSUserDefaults BUT I really want to do it using the AppDelegate. So at this point NSUserDefaults is not an option.
Now, I am using storyboards with a navigation controller. A screenshot is available here
Right now when I pass from the TemplateController to my PreviewController my code looks like this:
Reaching TemplateController from MainController or PreviewController
- (IBAction)showFrameSelector:(id)sender
{
UIStoryboard *storyboard;
storyboard = [UIStoryboard storyboardWithName:#"MainStoryboard_iPhone" bundle:nil];
TemplateController *templateController = [storyboard instantiateViewControllerWithIdentifier:#"TemplateController"];
templateController.frameDelegate = self;
[self presentViewController:templateController animated:YES completion:nil];
}
Passing the data from TemplateController to its controller's destiny (Either MainController or PreviewController)
- (void)collectionView:(UICollectionView *)collectionView didSelectItemAtIndexPath:(NSIndexPath *)indexPath
{
_selectedLabelStr = [self.frameImages[indexPath.section] objectAtIndex:indexPath.row];
[self.collectionView deselectItemAtIndexPath:indexPath animated:NO];
[self dismissViewControllerAnimated:YES completion:^{
if ([self.frameDelegate respondsToSelector:#selector(templateControllerLoadFrame:)])
{
[self.frameDelegate performSelector:#selector(templateControllerLoadFrame:) withObject:self];
}
}];
}
This loads the selected frame in PreviewController
- (void)templateControllerLoadFrame:(TemplateController *)sender
{
UIImage *tmp = [UIImage imageNamed:sender.selectedLabelStr];
_frameImageView.image = tmp;
}
My problem is, I don't have very clear what changes I have to do on the AppDelegate(it is untouched right now). What would be the best approach to accomplish this?
Main issue is when Tamplate is chosen before taking the still image. If I select the frame after taking the picture then it displays.
I am not certain that I understand your question. Stuffing an object into the app delegate solution may not be the best way forward. In fact I believe you ought to look at the delegation pattern that is used by Apple to communicate between view controllers. Please note that you appear to be doing half of the delegate pattern already. For example you make your PreviewController a frameDelegate of the TemplateController.
So I would think you'd have something like the following to transfer information from TemplateController back to the PreviewController. Note that I've included prepare for segue as that is a common pattern to push a data object forward (it will be called if you connect a segue from the PreviewController to the TemplateController and in your action method call performSegueWithIdentifier:#"SegueTitle"). Use of the "templateControllerDidFinish" delegation method is a common pattern used to push information back from TemplateController when it closes.
TemplateController.h
#class TemplateController;
#protocol TemplateControllerDelegate <NSObject>
-(void) templateControllerDidFinish :(TemplateController*)controller;
#end
#interface TemplateController : UIViewController
#property (nonatomic, weak) id <TemplateControllerDelegate>delegate;
...
#end
TemplateController.m
//! The internals for this method can also be called from wherever in your code you need to dismiss the TemplateController by copying the internal
-(IBAction)doneButtonAction:(id)sender
{
__weak TemplateController*weakSelf = self;
[self dismissViewControllerAnimated:YES completion:^{
[self.delegate templateControllerDidFinish:weakSelf];
}];
}
PreviewController.h
#import "TemplateController.h"
#interface PreviewController<TemplateControllerDelegate>
...
#end
PreviewController.m
#implementation
...
-(void) templateControllerDidFinish :(TemplateController*)controller
{
self.dataProperty = controller.someImportantData;
...
}
...
-(void)prepareForSegue:(UIStoryboardSegue*)segue sender:(id)sender
{
if ( [[segue identifier]isEqualToString:#""] )
{
TemplateController *tc = [segue destinationViewController];
tc.delegate = self;
tc.data = [someDataObjectFromPreviewController];
}
}
To fix this situation a bit more:
Add a segue from the PreviewController to the TemplateController
(Ctrl-drag from Preview view controller to the Template Controller
in the document outline mode)
Name the segue identifier in the identity inspector
Change your code that presents the view controller from:
(IBAction)showFrameSelector:(id)sender
{
UIStoryboard *storyboard;
storyboard = [UIStoryboard storyboardWithName:#"MainStoryboard_iPhone" bundle:nil];
TemplateController *templateController = [storyboard instantiateViewControllerWithIdentifier:#"TemplateController"];
templateController.frameDelegate = self;
[self presentViewController:templateController animated:YES completion:nil];
}
to
- (IBAction)showFrameSelector:(id)sender
{
[self performSegueWithIdentifier:#"SegueTitle"];
}
Add your data object to the target view controller as noted in prepareForSegue and you will be in good shape. Then use the delegate method to catch any data returned from your template (just add the data as properties to the controller and you should be golden)
You can see a better example of this delegation in a utility project template from Xcode (I just keyed this in..) I hope this information helps. You can get more information at these resources and also by searching Google and SO for iOS delegation :
Concepts in Objective C (Delegates and Data Sources)
Cocoa Core Competencies
How can I examine a list of all active objects that inherit UIViewController?
I'd like to know if an instance of MyViewController exists. Ideally I can get this information in a callback in UIApplicationDelegate (for example application:didReceiveRemoteNotification:).
I've tried logging something like navigationController.viewControllers w/ no luck. I've also tried topViewController and modalViewController properties on navigationController.
If you know for a fact that your rootViewController is a UINavigationController, you can iterate through the array of viewcontrollers and test it for a class type
BOOL success = NO;
NSArray *viewControllersArray = self.navigationController.viewControllers;
for (id vc in viewControllersArray)
{
if ([vc isKindOfClass:[MyViewController class]])
success = YES; // Found it!
}
I use the method performSegueWithIdentifier:sender: to open a new ViewController from a storyboard-file programmatically. This works like a charm.
But on every time when this method is being called, a new ViewController would be created. Is it possible to use the existing ViewController, if it exista? I don't find anything about this issue (apple-doc, Stack Overflow, ...).
The Problem is:
On the created ViewController the user set some form-Elements and if the ViewController would be called again, the form-elements has the initial settings :(
Any help would be appreciated.
Edit:
I appreciate the many responses. Meanwhile, I'm not familiar with the project and can not check your answers.
Use shouldPerforSegueWithIdentifier to either allow the segue to perform or to cancel the segue and manually add your ViewController. Retain a pointer in the prepareForSegue.
... header
#property (strong, nonatomic) MyViewController *myVC;
... implementation
-(BOOL) shouldPerformSegueWithIdentifier:(NSString *)identifier sender:(id)sender{
if([identifier isEqualToString:#"MySegueIdentifier"]){
if(self.myVC){
// push on the viewController
[self.navigationController pushViewController:self.myVC animated:YES];
// cancel segue
return NO;
}
}
// allow the segue to perform
return YES;
}
-(void) prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender
{
if([segue.identifier isEqualToString:#"MySegueIdentifier"]){
// this will only be called the first time the segue fires for this identifier
// retian a pointer to the view controller
self.myVC = segue.destinationViewController;
}
}
To reuse an existing UIViewController instance with a segue create the segue from scratch and provide your own (existing) destination (UIViewController). Do not forget to call prepareForSegue: if needed.
For example:
UIStoryboardSegue* aSegue = [[UIStoryboardSegue alloc] initWithIdentifier:#"yourSegueIdentifier" source:self destination:self.existingViewController]
[self prepareForSegue:aSegue sender:self];
[aSegue perform];
Following code makes singleton view controller.
Add them to your destination view controller implementation, then segue will reuse the same vc.
static id s_singleton = nil;
+ (id) alloc {
if(s_singleton != nil)
return s_singleton;
return [super alloc];
}
- (id) initWithCoder:(NSCoder *)aDecoder {
if(s_singleton != nil)
return s_singleton;
self = [super initWithCoder:aDecoder];
if(self) {
s_singleton = self;
}
return self;
}
I faced this problem today and what I have done is to create the view controller manually and store it's reference.
Then every time I need the controller, check first if exists.
Something like this:
MyController *controller = [storedControllers valueForKey:#"controllerName"];
if (!controller)
{
controller = [[UIStoryboard storyboardWithName:#"MainStoryboard_iPhone" bundle:NULL] instantiateViewControllerWithIdentifier:#"MyControllerIdentifierOnTheStoryboard"];
[storedControllers setValue:controller forKey:#"controllerName"];
}
[self.navigationController pushViewController:controller animated:YES];
Hope it helps.
Create a property for the controller.
#property (nonatomic, weak) MyController controller;
And use some kind of lazy initialization in performSegueWithIdentifier:sender
if (self.controller == nil)
{
self.controller = [MyController alloc] init]
...
}
In this case, if controller was already created, it will be reused.
Firstly you would be going against Apple's design in Using Segues: "A segue always presents a new view controller".
To understand why it might help to know that what a segue does is create a new view controller and then the perform calls either showViewController or showDetailViewController depending on what kind of segue it is. So if you have an existing view controller just call those methods! e.g.
- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath{
Event *object = [self.fetchedResultsController objectAtIndexPath:indexPath];
self.detailViewController.detailItem = object;
[self showDetailViewController:self.detailViewController.navigationController sender:self];
}
You would need to make the Viewcontroller into a singleton class.
I'm new to using the split view for creating iPad applications. When I first create the project just using the standard MasterDetail Application template (Xcode 4.2), it creates a MasterViewController and a DetailViewController. The template has the following method that is called when a row is selected from the popover table (master detail view controller):
- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath
if (!self.detailViewController)
{
self.detailViewController = [[DetailViewController alloc] initWithNibName:#"DetailViewController" bundle:nil];
}
[self.navigationController pushViewController:self.detailViewController animated:YES];
Now I understand when you are using a regular navigation controller if you are programing for an iPhone you just do this type of thing to push on another view controller on to the stack. However, with this template, it just pushes the detail view onto the popover rather than updating what is already present. I'm confused as what I need to update to select something from the pop over (master detail view), and then have the detailView update.
Update:
To try and test out the "detailItem" that is already setup for you in the DetailViewController, I commented out the pushViewController and added the following:
//[self.navigationController pushViewController:self.detailViewController animated:YES];
self.detailViewController.detailItem = #"Test";
// setter in detailViewController
- (void)setDetailItem:(id)newDetailItem
{
if (_detailItem != newDetailItem) {
_detailItem = newDetailItem;
// Update the view.
[self configureView];
}
if (self.masterPopoverController != nil) {
[self.masterPopoverController dismissPopoverAnimated:YES];
}
}
- (void)configureView
{
// Update the user interface for the detail item.
// detailDescriptionLabel.text is a IBOutlet to the label on the detailView
if (self.detailItem) {
self.detailDescriptionLabel.text = [self.detailItem description];
}
}
According to this code, the text of the label on the detailViewController should be updated. However, when I do click on the item in the master view controller table, nothing happens.
There are a couple different ways you could do it. First off, like you said, remove the pushViewController call (I don't know why Apple's template does this... maybe just to show you you can?).
Next, let your MasterViewController know about the DetailViewController that is already displayed. I usually set master.detailViewController = detailViewController in the appDelegate.
Remember, the DetailViewController is already being displayed, so you won't always need to realloc it (unless you are replacing it with some other view)
First Option
Use delegate calls to set the information. Declare a protocol to pass information to the detailView and have it display it appropriately. Here is a tutorial describing this in more detail.
Second Option
Pass DetailViewController some data & override the setter to refresh the detailView. Here is a tutorial describing this in more detail.
// in DetailViewController
- (void)setDetailItem:(id)newDetailItem {
if (detailItem != newDetailItem) {
[detailItem release];
detailItem = [newDetailItem retain];
// Update the view.
navigationBar.topItem.title = detailItem;
NSString * imageName = [NSString stringWithFormat:#"%#.png",detailItem];
[self.fruitImageView setImage:[UIImage imageNamed:imageName]];
}
}
Edit: Just looked at the template again, and setDetailItem type code is already in there, but the code is creating a completely new detailView so the detailView that is viewable on the splitViewController is not changed at all.
I am loading new views for a small iphone app, and was wondering how to pass details from one to another?
I am loading a tableview full of data from and xml file, then once clicked a new view is brought in via:
- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath {
SubInfoViewController *subcontroller = [[SubInfoViewController alloc] initWithNibName:#"SubInfoView" bundle:nil];
[self presentModalViewController:subcontroller animated:YES];
[subcontroller release];
}
Next step would be to tell the newly loaded view which row had just been loaded?
Any idea, thoughts more than welcome, and please be gentle big newbie...
I typically create my own init method to do things like this. I think it would likely be better to pass in the corresponding "model" object represented by the tableView row, rather than the row number itself, like this:
In SubInfoViewController.h
#interface SubInfoViewController : UIViewController {
YourObject *yourObject;
}
#property (nonatomic, retain) YourObject *yourObject;
Then in SubInfoViewController.m:
- (SubInfoViewController*)initWithYourObject:(YourObject*)anObject {
if((self = [super initWithNibName#"SubInfoView" bundle:nil])) {
self.yourObject = anObject;
}
return self;
}
You'd create and present it this way:
// assuming you've got an array storing objects represented
// in the tableView called objectArray
SubInfoViewController *vc = [[SubInfoViewController alloc] initWithYourObject:[objectArray objectAtIndex:indexPath.row]];
[self presentModalViewController:vc animated:YES];
[vc release];
This could be adapted pretty easily to allow you to pass in any type of object or value (such as a row number if you still want to do that).
Add an instance variable to your view controller and declare a property corresponding to it, so after you alloc, init it, set it like subcontroller.foo = Blah Blah.