is there a way to identify the segue identfier used to navigate, inside the destination viewcontroller.
Well in that case in the viewController you are coming from override prepareForSegue: and pass some data in to the destination viewController that will allow it to decide what specific code to run.
- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender
{
if ([segue.identifier isEqualToString:#"SegueIdentifier"]) {
YourViewController *vc = segue.destinationViewController;
vc.yourData = yourData;
}
}
the in viewDidLoad of the destination check the value of yourData and execute your custom code
Related
I'm completely new to objective c and ios development, I'm simply trying to navigate to a new scene on my storyboard, and upon navigating change the text of a UIlabel to something.
The way I have this set up is I have a View controller and a tableview controller, each with their own header and implementation files. I'm using a segue from a button on the view controller to navigate to the tableview.
I did read this stack overflow post (How do I pass information between storyboard segues?) which explains how to pass values on a segue and have implemented it as such:
-(void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender{
NSLog(#"prepareForSegue: %#", segue.identifier);
if([segue.identifier isEqualToString:#"navtotablebut"])
{
TableViewController *testcontroller = segue.destinationViewController;
testcontroller.testpass.text = #"Testing123";
NSLog(#"%#",[NSString stringWithFormat:#"testpass has been changed to %#", testcontroller.testpass.text]);
}
}
The logs verify that this segue method does get called, and it is able to correctly identify the id I gave it (navtotablebut). I then attempt to set the value of my UIlabel's text property on my tableview controller to a simple string "Testing123". However not only does this change not reflect on the new screen, but my print statement afterwards seems to think testcontroller.testpass.text is equal to (null).
Am I doing something horribly wrong here?
You are setting the value of label testcontroller in TableViewController before the view of `TableViewController ' is drawn.
Please note: update the view in viewdidLoad or viewDidLayoutSubviews if using Autolayout.
Best way is pass your value as a string to other view controller and then populate.
Simply grab a reference to the target view controller in prepareForSegue: method and pass any objects you need to there. Here's an example...
- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender
{
// Make sure your segue name in storyboard is the same as this line
if ([[segue identifier] isEqualToString:#"YOUR_SEGUE_NAME_HERE"])
{
// Get reference to the destination view controller
YourViewController *vc = [segue destinationViewController];
// Pass any objects to the view controller here, like...
[vc setMyObjectHere:object];
}
}
also with performSegueWithIdentifier:sender: method to activate the transition to a new view based on a selection or button press.
// When any of my buttons are pressed, push the next view
-(IBAction)buttonPressed:(id)sender
{
[self performSegueWithIdentifier:#"MySegue" sender:sender];
}
// This will get called too before the view appears
-(void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender
{
if ([[segue identifier] isEqualToString:#"MySegue"]) {
// Get destination view
SecondView *vc = [segue destinationViewController];
// Get button tag number (or do whatever you need to do here, based on your object
NSInteger tagIndex = [(UIButton *)sender tag];
// Pass the information to your destination view
[vc setSelectedButton:tagIndex];
}
}
In TableViewController, You need to create property,
TableViewController.h
#property (nonatomic, strong) NSString *subject;
you pass value like that,
In ViewController,
-(void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender
{
if([[segue identifier]isEqualToString:#"Detail"])
{
TableViewController *testcontroller = segue.destinationViewController;
testcontroller.testpass.text = #"Testing123";
detailView.subject = testcontroller.testpass.text;
}
}
I got two segue's which lead to the same viewController. There are 2 buttons which are connected to the same viewController using 2 segues. In that viewController I need to check which button was clicked. So actually I need to check which segue was used/preformed. How can I check this in the viewControllers class? I know there is the prepareForSegue method, but I cannot use this for my purpose because I need to put the prepareForSegue in the class where the 2 buttons are, and I don't want it there but I want it in the viewControllers class because I need to access and set some variables in that class.
You need to set a variable of the second viewcontroller in the prepareforsegue method of first one. This is how it is done:
- (void) prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender
{
if([segue.identifier isEqualToString:segueIdentifier1])
{
SecondViewController *secondVC = (SecondViewController *)segue.destinationViewController;
if(sender.tag == ...) // You can of course use something other than tag to identify the button
{
secondVC.identifyingProperty = ...
}
else if(sender.tag == ...)
{
secondVC.identifyingProperty = ...
}
}
}
Then you can check that property in the second vc to understand how you came there. If you have created 2 segues in the storyboard for 2 buttons, then only segue identifier is enough to set the corresponding property value. Then code turns into this:
- (void) prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender
{
if([segue.identifier isEqualToString:segueIdentifier1])
{
SecondViewController *secondVC = (SecondViewController *)segue.destinationViewController;
secondVC.identifyingProperty = ...
}
else if([segue.identifier isEqualToString:segueIdentifier2])
{
SecondViewController *secondVC = (SecondViewController *)segue.destinationViewController;
secondVC.identifyingProperty = ...
}
}
So firstly you need to set your segues identifier directly in storyborads or through your code using the performSegueWithIdentifier method.
Independently the way you choosed, your view controller will fire the following method, so you need to override it to know which segue was sending the message, you do like this:
-(void) prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender {
if ([segue.identifier isEqualToString:#"ButtonSegueIdentifierOne"]) {
// button 1
}
if ([segue.identifier isEqualToString:#"ButtonSegueIdentifierTwo"]) {
// button 2
}
}
I started using storyboards but am noticing one very significant difference: The storyboard appears to be instantiating a new ViewController each time I navigate back and forth.
Example: I create two new Xcode projects based on the Master-Detail template. In Case 1, I use the Storyboard and in Case 2 I use the .xib.
Normally I would expect these to behave identically, but they don't!
In both of the DetailViewController.m I add the following method:
-(void)viewDidAppear:(BOOL)animated{
if (xposition ==0) {
xposition=50;
}else{
xposition = xposition+50;
}
NSLog(#"xposition update %d", xposition);
}
(I have also declared the xposition as an "int" instance variable in the header):
When I run the Storyboard version and tap the "+" and navigate in and out of the DetailViewController then my NSLog statement keeps giving me "xposition update 50".
By contrast, for the .xib version I get my expected behavior where each time I navigate in and out of the DetailViewController that the "position" increments by 50: so 50, 100, 150 etc.
How do I fix Storyboard to make it behave in the same way as the .xib based version. Specifically, I want to only instantiate the DetailViewController once.
EDIT: Answering my own question. I got some help on this and wanted to post the answer that worked for me.
When you first perform the segue store the destination viewcontroller in a property (see method "PrepareForSegue". My VC is called MyViewController)
Then create the delegate method called "shouldPerformSegueWithIdentifier" and use this to intercept the segue and manually present the stored ViewController for all subsequent segues.
- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender{
UIViewController *destination = segue.destinationViewController;
NSLog(#"identifier = %#", [segue identifier]);
if([[segue identifier] isEqualToString:#"mySegue"]) {
self.myViewController = (MyViewController*)destination;
NSLog(#"Saving myViewController for later use.");
}}
- (BOOL)shouldPerformSegueWithIdentifier:(NSString *)identifier sender:(id)sender {
if([identifier isEqualToString:#"mySegue"]) {
if(self.myViewController != nil) {
NSLog(#"Using the saved myViewController.");
[self.navigationController pushViewController:self.myViewController animated:YES];
return NO;
}else {
return YES;
}
}
return YES;}
When you navigate back and forth your storyboard pops off your DetailViewController. Because it is not retained by anything else it will be released, this is normal behavior.
If you want to keep the instance you'll have to retain it in the ViewController you are calling it from and use it later on again. Check this question for an example
Edit:
I think you solved the problem but here is an example:
Create a property for you viewcontroller in your interface, say myViewController
Retain the viewcontroller in the prepareForSegue method:
- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender{
[self setMyViewController:[segue destinationViewController]];
}
This it not leaking memory, your example could leak in some cases. Check out this guide here.
The next time the seque will be performed check if the property is already set and if so use it:
- (BOOL)shouldPerformSegueWithIdentifier:(NSString *)identifier sender:(id)sender {
if([self myViewController] != nil){
[[self navigationController] pushViewController:[self myViewController] animated:YES];
return NO;
}else{
return YES;
}
}
I have created a simple unwind segue using the storyboard tools. I have created the following event handler in the view I want to unwind to:
-(IBAction)quitQuiz:(UIStoryboardSegue *)segue {
NSLog(#"SEGUE unwind");
}
This fires correctly and unwinds the segue (the message gets logged).
When the user quits the quiz I would like to pass some data back and have been struggling with how to achieve this. Can anyone advise?
Thanks Jeff. After watching WWDC video 407 I have a clear solution.
In the view controller that is the target of the unwind you should create a method that takes a single UIStoryboardSegue parameter and returns an IBAction. The UIStoryboardSegue has a method to return the source view controller! Here is the example taken from the video (credit to Apple).
- (IBAction)done:(UIStoryboardSegue *)segue {
ConfirmationViewController *cc = [segue sourceViewController];
[self setAccountInfo:[cc accountInfo]];
[self setShowingSuccessView:YES];
}
Getting data back from an unwind segue is explained very nicely in this apple talk, second half of the presentation (edit: starts from 37:20)
In particular, in an unwind segue the [segue sourceViewController] is the still active view controller from which the unwind event originated, so just access your properties as usual.
Add the function prepareForSeque in the controller being closed.
-(void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender
This function is called before the unwind segue is called (in your example you called it quitQuiz).
As you can see, it also has a sender parameter so that you can find out who called the unwind and collect the relevant data accordingly.
For example of the WWDC 407 video, if you clicked the reset button you would not set the accountInfo and if you clicked the done button you would.
Set up a delegate and inform your source view controller about quitting the quiz and send back the data. Don't forget to set the source view controller as the delegate of the destination view controller.
// DestinationViewController.h
#protocol DestingationDelegate;
#interface
...
#property (assign) id<DestinationDelegate> delegate;
...
#end
#protocol DestinationDelegate
-(void)didQuitQuiz:(NSDictionary*)infoDict;
#end
// DestinationViewController.m
-(IBAction)quitQuiz:(UIStoryboardSegue *)segue {
NSLog(#"SEGUE unwind");
if (self.delegate) [self.delegate didQuitQuiz:infoDict];
}
// SourceViewController.h
#import DestinationViewController.h
#interface SourceViewController : ViewController <DestinationDelegate>
....
// SourceViewController.m
-(void)didQuitQuiz:(NSDictionary *)infoDict {
if (infoDict) {
// do something with the data
}
}
-(void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender {
...
destinationViewController.delegate = self;
}
Yes,
For that, you will need to make properties, which holds your data to be sent from another view controller:
- (IBAction)unwindSelectFriendsVC:(UIStoryboardSegue *)segue
{
if ([segue.sourceViewController isKindOfClass:[ChildVC class]]) {
ChildVC *child = (ChildVC *) segue.sourceViewController;
//here we are passing array of selected friends by arrSelectedFriends property
self.arrFriendList = child.arrSelectedFriends;
[self.tableView reloadData];
}
}
Passing data between view controllers is frequently accomplished using protocols. Here's an example:
In your quiz view controller header, declare a similar protocol definition:
#protocol JBQuizViewControllerDelegate <NSObject>
#required
- (void)quizController:(id)controller didQuitWithState:(NSString *)state;
#end
In your presenting view controller's prepareForSeque: method, wire up the delegate:
JBQuizViewController *destination = (JBQuizViewController *)segue.destinationViewController;
destination.delegate = self;
Then, in your presenting view controller, handle the delegate protocol's quizController:didQuitWithState: method.
Finally, once the user quits your quiz, you should notify the delegate using the protocol, passing in the state or whatever data you want to expose.
I hope I'm not asking something that's been already answered (but I found no answer to this, so hopefully I'm not).
I have an app in the current xcode version, using segues and navigationController. I need to pass data from one view to the other - what's the easiest way to do this? I ran onto some sharedData thing that could be possibly hooked onto the performSegueWithIdentifier method but don't know how to use it (or whether it is the right choice to do it like this).
Thanks
A segue has two view controllers: sourceViewController and destinationViewController. When UIKit executes a segue, it sends a prepareForSegue:sender: message to the source VC. You can override that method in your view controller subclass to pass data to the destination VC.
For example, suppose you have a master view controller with a table view of movies, and when the user clicks a row in the table view, you want to segue to a detail view controller for the movie.
#implementation MasterViewController
...
- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender
{
DetailViewController *detailVC = segue.destinationViewController;
NSIndexPath *selectedPath = [self.tableView indexPathForSelectedRow];
detailVC.movie = [self movieForIndexPath:selectedPath];
}
This is explained in the Introducing Interface Builder Storyboarding video from WWDC 2011.
It's also worth noting that when the segue's origin is a table view cell, or the accessory button of a table view cell, the sender argument of prepareForSegue:sender: is the table view cell.
I think the best way is to import header for the view controller that will be shown in controller that is performing segue. And then use it's accessors or other methods to pass needed data inside prepareForSegue:
// In FirstViewController.h
#import "SecondViewController.h"
- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender {
if ([[segue identifier] isEqualToString:#"SegueToSecondViewController"]) {
// Get destination view controller and don't forget
// to cast it to the right class
SecondViewController *secondController = [segue destinationViewController];
// Pass data
secondController.dataArray = self.someDataArray;
secondController.name = #"Fancy name";
}
}
When you want data back from second to first, I suggest to use delegate:
// In FirstViewController.h
#import "SecondViewController.h"
#import "SecondViewControllerDelegate.h"
- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender {
if ([[segue identifier] isEqualToString:#"SegueToSecondViewController"]) {
SecondViewController *secondController = [segue destinationViewController];
// Declare first view controller as a delegate
secondController.delegate = self;
// Pass data
secondController.dataArray = self.someDataArray;
secondController.name = #"Fancy name";
}
}
// Second controller's delegate method,controller
// ie. used to return data after second view is dismissed
- (void)secondControllerFinishedSomeTask:(NSArray *)someReturnedData {
// Do something with returned data
}
When you want data back from second to first, better way is to use Unwind Segues.