I have this simple project where, when a button on a second ViewController (SecondViewController) is pressed a Delegate function send a string to the first ViewController and Unhide a new button which is not visible.
I have no problem now doing this however, if I add a third view between these to windows the function stops working.
Here what I mean:
In order to do this I use
In ViewController.h:
#interface ViewController : UIViewController <SecondViewControllerDelegate>
In ViewController.m I implemented a Segue function which detected an Identifier and send the value to second view :
-(void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender{
if ([segue.identifier isEqualToString:#"to2"]) {
SecondViewController *SecondView = segue.destinationViewController ;
SecondView.delegate = self;
}
}
-(void)done:(UIButton*)name{
[self dismissViewControllerAnimated:YES completion:nil];
NSLog(#"back to first view, name=%# ", name);
level2But.hidden = NO;
}
To return to the first window i have created a returnButton in SecondViewController.h:
#protocol SecondViewControllerDelegate <NSObject>
-(void) done:(UIButton*)returnButton; //variable passed to ViewController
#end
#interface SecondViewController : UIViewController{
IBOutlet UIButton *returnButton;
id delegate; //declare delegate as an object
}
#property (nonatomic, strong) id <SecondViewControllerDelegate> delegate;
-(IBAction)returnButtonPressed:(id)sender;
In SeconViewController.m I have:
-(IBAction)returnButtonPressed:(id)sender{
[self.delegate done:returnButton];
}
This code is working just fine However if I had a third View It stops Working.
This is not working anymore.
AnySuggestion? Any Help?
This is the project file:
http://goo.gl/3rJOje
I did checked your code and I could see the self.delegate is nil and hence you are not able to move in SecondViewController.m.
-(IBAction)returnButtonPressed:(id)sender{
[self.delegate done:returnButton];
}
so make sure you pass the delegate.
Also if you want to know how to pass the data(delegate) then go through the below tutorial :
http://www.appcoda.com/storyboards-ios-tutorial-pass-data-between-view-controller-with-segue/
Related
I've a TableViewController in which I'm saving the selected cells in an NSMUtableArray. After selecting these cells user clicks on a confirm button and in this button action I'm trying to pass that NSMUtableArray so that I can display it in another viewController tableView
#import <UIKit/UIKit.h>
#protocol SelectedDXDelegate;
#interface AddDXTableViewController : UITableViewController
#property (nonatomic, strong) NSMutableArray *favDXArray;
#property (strong, nonatomic) UISearchController *searchController;
#property (nonatomic, strong) DX *AddEditDX;
#property (weak) id<SelectedDXDelegate> delegate;
- (IBAction)confirmPressed:(id)sender;
#end
#protocol SelectedDXDelegate <NSObject>
#required
-(void)getSelectedDX:(NSMutableArray *)DXselected;
#end
So when confirm button is pressed
- (IBAction)confirmPressed:(id)sender {
[self.delegate getSelectedDX:selectedDX];
[self.navigationController popViewControllerAnimated:YES];
}
it gets me to the
-(void)getSelectedDX:(NSMutableArray *)DXselected
{
myDXSelected = DXselected;
}
But it crashes the app here at reloadData in
- (void)viewWillAppear:(BOOL)animated {
[super viewWillAppear:animated];
[self.DXTableView reloadData];
}
You seem to have mixed up which view controller should be the delegate and which is the delegator. Also, you are just allocating a new instance of the AddDXTableViewController and assigning this as the delegate. This won't work; you need to have the existing instance of your view controller set as the delegate.
From what I can tell from your question, it is actually an instance of DXViewController that is to be the delegate of AddDXTableViewController
Presumably in DXViewController you have some code something like:
AddDXViewController *newViewController = [self.storyboard instantiateViewControllerWithIdentifier:#"AddDXViewController"];
[self.navigationController pushViewController:newViewController animated:YES];
What you need to do is set your delegate at this point:
AddDXViewController *newViewController = [self.storyboard instantiateViewControllerWithIdentifier:#"AddDXViewController"];
newViewController.delegate = self;
[self.navigationController pushViewController:newViewController animated:YES];
Having said all of that, since you are using a storyboard, a delegate is probably an unnecessarily complicated way of achieving your requirement; You can use a segue to move between the first and second view controller and an unwind segue to return back to the first. You can then implement prepareForSegue in the second view controller and use that to provide the array back to the first view controller
You have to make the UIViewController added in storyboard to AddDXTableViewController type in the identity inspector tab in story board.
See here the image
Here you can see the class type is ViewController, click on the dropdown and select the type to AddDXTableViewController
then type cast the viewController to AddDXTableViewController. As per my guess the instantiateViewControllerWithIdentifier: returns UIViewController which does not have delegate may cause the crash
AddDXTableViewController *addDXTVC = (AddDXTableViewController *)[self.storyboard instantiateViewControllerWithIdentifier:#"DXViewController"];
addDXTVC.delegate = self;
Let me know If it works
I am trying to reload my table view controller after inserting an item using core data. I am using storyboards to present my modal view controller and am setting the delegate of the destination view controller in prepare to segue but i believe that is the issue, as my didAddCollection method is not being triggered. I am not sure what i am missing here. i used iOS TableView Reload after dismissing modal as the base for the current code i have.
In my CCNewCollectionViewController.h
#protocol NewCollectionDelegate <NSObject>
-(void) didAddCollection;
#end
#interface CCNewCollectionViewController : UIViewController {
id delegate;
}
#property (nonatomic, retain) id <NewCollectionDelegate> delegate;
In my CCNewCollectionViewController.m
#implementation CCNewCollectionViewController
#synthesize delegate;
// save data
[self.delegate didAddCollection];
// dismiss view controller
In my CollectionTableViewController.m
#interface CollectionTableViewController () <NSFetchedResultsControllerDelegate, NewCollectionDelegate>
-(void) didAddCollection {
[self.tableView reloadData];
}
- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender {
[[segue destinationViewController] setDelegate:self];
}
A very silly mistake. When setting the delegate of the destination view controller, i was actually setting the delegate of the UINavigationController instead of the CCNewCollectionViewController.
UINavigationController *nc = [segue destinationViewController];
CCNewCollectionViewController *vc = nc.viewControllers[0];
[vc setDelegate:self];
I changed my prepareForSegue code to this and it solved my problems!
Not sure if this will solve your problem, but I think it is more typical to just create a weak delegate property. No need to synthesize.
#interface CCNewCollectionViewController : UIViewController
#property (nonatomic,weak) id <NewCollectionDelegate> delegate;
...
#end
See here for more information about working with protocols.
I'm having some trouble getting a viewcontroller to respond to a action inside a modal viewcontroller.
I have a sidebar with a settings button. This button presents a settings viewcontroller modally, and I want my sidebar to respond when a user taps the log out button on my settings viewcontroller.
In my settingsTableViewController.h I set up the delegate like this:
#class SettingsTableViewController;
#protocol SettingsTableViewControllerDelegate <NSObject>
- (void)loggedOutUser:(SettingsTableViewController *)viewController;
#end
#interface SettingsTableViewController : UITableViewController
#property (nonatomic, weak) id <SettingsTableViewControllerDelegate> delegate;
....
And then in the settingsTableViewController.m I synthesize the delegate and call the delegate method like so:
#synthesize delegate;
....
- (IBAction)logOut:(id)sender {
[self.delegate loggedOutUser:self];
....
}
Furthermore, in my responding menuTableViewController.h I set it up like so:
#interface MenuTableViewController : UITableViewController <SettingsTableViewControllerDelegate>
And then finally I set the delegate in the prepareForSegue method in my menuTableViewController.m:
- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender {
....
if ([[segue identifier] isEqualToString:#"settingsSegue"]) {
SettingsTableViewController *stvc = [segue destinationViewController];
stvc.delegate = self;
}
....
}
I simply cannot figure out what's causing this.
My guess is that the stvc.delegate = self doesn't do what it's supposed to, because the menuTableViewController responds to the delegate of another viewcontroller as well (not modal), and here I had to set the delegate = self in the viewDidLoad method, but before the [self viewDidLoad] call, as placing it after did not work.
Any help that could resolve this issue would be greatly appreciated! I've been struggling with this for too long now... Thanks!
Turns out my destinationViewController is actually a navigationController, so the delegate is not set correctly. Thanks to remus for telling me to set a breakpoint to check if the delegate was set correctly.
I fixed it by writing
SettingsTableViewController *stvc = ((UINavigationController *)[segue destinationViewController]).viewControllers[0];
instead.
I'm currently trying to have a better understanding on how the mechanisms of passing data between controllers work and I'm a little confused especially when passing data back from a second view controller to the main view controller.
This is what I have that works but don't fully understand. I have two view controllers, in the first one I have a button that when clicked it basically goes to the second view controller and a label which shows a message sent from the second view controller. In the second view controller I have a button and a textField, the button basically sends whatever is in the textfield to the label in main view controller.
Here is the code...
// FirstVC.h
#import <UIKit/UIKit.h>
#import "SecondVC.h"
#interface FirstVC : UIViewController <passNames>
#property (nonatomic, strong) NSString* firstNameString;
#property (weak, nonatomic) IBOutlet UILabel *firstNameLabel;
#end
//FirstVC.m
#import "FirstVC.h"
#implementation FirstVC
-(void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender
{
if ([[segue identifier]isEqualToString:#"secondController"])
{
UINavigationController *navController = segue.destinationViewController;
SecondVC *vc2 = (SecondVC*)navController.topViewController;
[vc2 setDelegate:self];
}
}
-(void)viewWillAppear:(BOOL)animated
{
self.firstNameLabel.text = _firstNameString;
}
-(void)setFirstName:(NSString *)firstName
{
_firstNameString = firstName;
}
#end
//SecondVC.h
#import <UIKit/UIKit.h>
#protocol passNames <NSObject>
-(void)setFirstName:(NSString*)firstName;
#end
#interface SecondVC : UIViewController
#property (retain)id <passNames> delegate;
- (IBAction)send:(UIBarButtonItem *)sender;
#property (nonatomic, strong) NSString *firstNameString;
#property (weak, nonatomic) IBOutlet UITextField *firstNameText;
#end
//SecondVC.m
#import "SecondVC.h"
#import "FirstVC.h"
#interface SecondVC ()
#end
#implementation SecondVC
- (IBAction)send:(UIBarButtonItem *)sender
{
_firstNameString = _firstNameText.text;
[[self delegate]setFirstName:_firstNameString];
[self dismissViewControllerAnimated:YES completion:nil];
}
#end
Can someone explain how the prepareForSegue method works in the above code? The reason for this question is because I added an NSLog and it looks like this method is only called in the transition from main view controller to the second controller. Why is this method needed if it is not called when transitioning from second view controller to main view controller which in my case is what I'm doing? It makes sense to use it when passing data from main view controller to a second controller not on the case shown above.
Can some explain the whole mechanism when passing data back to the main view controller?
FYI, I do understand about protocols and delegation.
Thanks a lot.
In your case, you are setting your delegate method of the second view controller to self in mainViewController in you prepareForSegue. This means that apart from navigating to the SecondViewController, you are implementing the callback mechanism in your main view controller, so that your delegate method gets called when the value is passed from the second view controller and this delegate method collects the value as a parameter to handle it in the main View Controller. You might have set the delegate of VC2 as self inn your prepareForSegue because you are creating the instance of VC2 in this method to navigate to the second controller.
Your goal is to hand back the data, like this:
[[self delegate] setFirstName:_firstNameString];
But you can't do that unless you know who to send setFirstName: to, and the compiler won't let you do it unless you guarantee that whoever you are sending setFirstName: to can accept that message.
That is what prepareForSegue prepares. FirstVC has declared that it adopts the passNames protocol, which means that it implements setFirstName:. And now you are saying:
[vc2 setDelegate:self];
...where self is the FirstVC instance. This solves both problems at once. The SecondVC instance (vc2) now has a delegate (the FirstVC instance), it is the right object to send the info back to, and because its delegate is declared as adopting passNames, we know that SecondVC can actually send setFirstName: to that delegate.
Now to the heart of your actual question: The reason for doing this in prepareForSegue is merely that this is the only moment when the FirstVC instance and the SecondVC instance "meet" one another! There is no other moment when the FirstVC instance has a reference to the SecondVC instance so as to be able to call setDelegate on it in the first place. If you weren't using segues and storyboards, the FirstVC would simply create the SecondVC instance directly - and would set itself as its delegate, just as you do:
SecondVC *vc2 = [SecondVC new];
UINavigationController *nav = [
[UINavigationController alloc] initWithRootViewController: vc2];
[vc2 setDelegate:self];
[self presentViewController: nav animated: YES completion: nil];
This is one reason I don't like storyboards: they muddy the story. It's all so simple and obvious when you don't use them and just do everything directly like this.
In FirstViewController I have a tableview. A button is clicked to push SecondViewController where an item is typed in and a button is pressed to add the item.
In SecondViewController.h file there is:
#protocol SecondViewControllerDelegate <NSObject>
-(void)itemAdded:(NSString *)item;
#property (nonatomic, weak)id <SecondViewControllerDelegate> delegate;
In `SecondViewController.m
- (IBAction)myButton:(id)sender {
[self.delegate itemAdded:#"someText"];
}
In FirstViewController.h
#interface SecondViewController: UITableViewController <UIAlertViewDelegate, SecondViewControllerDelegate>
In FirstViewController.m
-(void)itemAdded: (NSString *) item{
[self.items addObject: item];
}
Everything is working fine except that the [self.delegate itemAdded:#"someText"]; doesn't call the itemAdded function in the FirstViewController can anyone help?
The problem is likely that the delegate of the second view controller is nil. Where ever you create the second view controller, presumably somewhere in the first view controller, you need to set secondViewController.delegate = self so that when the second view controller needs to call back to the delegate, it's pointing to the first controller instead of nil.
Also, you have declared the SecondViewController class as a SecondViewControllerDelegate, but this is incorrect. A second view controller wouldn't be the delegate of itself, rather a FirstViewController will be. You need to move to the interface of FirstViewController, then the compiler won't complain when you try to set a FirstViewController as the delegate to the SecondViewController.