I have a problem where I am able to pass all data to a push view controller using
[self performSegueWithIdentifier:#"Expense" sender: self];
and
-(void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender
However I do not know how to get back data when the view controller is popped out. I have a couple of arrays that need to be passed from a popped view controller to parent view controller.
Create a class to serve as the data model for your application and have it include the arrays you need to pass around. Create an object of that class in your first controller, share it with the second controller during prepareForSegue:, let the second controller update it, and read the new values when the parent's view appears again.
You should use segues to pass data forward and Delegate Methods to send data back in your navigation stack. That is the recommended approach. I answered a similar question earlier. Although the question may sound different, the underlying solution should work in your case as well.
Related
In UINavigationViewController, if I wanna pass values from one controller to next, just call - (void) prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender , but what should I do if I wanna pass values from one viewController to previous viewController
I remember running across this same issue a few projects back. I can't find the my code to answer this question, but I did find a few tutorials.
http://prateekvjoshi.com/2014/02/16/ios-app-passing-data-between-view-controllers/
http://www.infragistics.com/community/blogs/torrey-betts/archive/2014/05/29/passing-data-between-view-controllers-ios-obj-c.aspx
and hence the concept of delegate came forth from segues.
Basically Segues are transition from one view to another but the child view is over the parent view, (inside a stack) so the parent view is still loaded.
So if u put segues everywhere and pass values between them then objects will keep on be creating and stored inside a stack and thus the cycle carries on.
So delegates was introduced.
Delegate is a method by which a child view controller(the later one) sends information using the inbuild delegate methods or self created protocol methods to the Previous view controller(the first one).
Here the one sending the information(later view) declares a delegate object, and a delegate method.
Which is then implemented by the recieving class(first view). So even after the later view is popped from the stack, the information is sent back to the root view by the delegate method.
Go through the documentation, its given in a more appropriate way
Hope this helps
Set previous view controller as delegate of current view controller and pass any values you want. This is standard approach.
When using a UINavigationController, when the user is "diving in deeper" (pushing yet another controller on the stack), I have an opportunity to handle that in
-(void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender
But how do I handle the opposite? When the user presses the back button, and a controller becomes the top controller again, I'd like it to potentially update some state because the controllers on the stack may have changed some things I want to reflect in the now visible controller.
Or, by analog, when I use modal segues to present new controllers, I get to pick a method that is called as an unwind segue when the presented controller exits. How can I do the same with navigation stack managed controllers?
(feel free to put a better title on this)
It turns out that you can disambiguate based on the response to isMovingToParentViewController. If it is YES your controller has just been placed topmost on the stack. If it is NO, your controller is returning to topmost, another push on top of it being popped. Example:
-(void)viewWillAppear:(BOOL)animated{
if (self.isMovingToParentViewController == NO) { // returning from even higher controller
[self updateForChangesThatMayHaveHappenedInSubController];
}
[super viewWillAppear:animated];
}
You can use the viewWillAppear: method to update the ui before the view becomes visible. If you want to pass data back up the chain, you should assign yourself as the delegate to your child and call an update function on the delegate before popping.
To have many clients (viewControllers in this case) update their views in response to a change of some shared data, you should use NSNotifications, or you should have the viewControllers observe certain values on the shared data-object (KVO).
ViewController should be as autistic as possible, meaning that they know all about the interface of downstream viewControllers, but have absolutely no idea about what viewController is upstream (talking back to an upstream viewController is usually done through delegation, and only to signal events that might indicate some change in viewController hierarchy, not in shared data state).
Checkout out the stanford lectures by Paul Hegarty, he explains this much better then I can.
I have a form and it gives users an advance mode. I've already googled and looked around at different SO questions (sharing data between controllers, protocols, and passing data between segues) but I'm wondering if there's a better way.
Is there a way for me to have some sort of "master controller" that holds all the data while going back and forth between 3 different controllers?
If I can just hold the data for the second controller and allow my user to make that quick advance edit in the third while keeping it's data intact, that'll do for now.
Thanks in advance
Here's a quick walkthrough of my app:
FirstViewController: User selects an option
SecondViewController: User does some editing while storing that option
(*Optional)ThirdViewControl: User one more quick edit using a web view
*xcode5/iOS7
If you are passing data from one view controller to the next and you are using segues, then call a method on the next view controller in line from prepareForSegue. For example, when segueing between ViewController1 and ViewController2, add this code to ViewController1 and repeat as necessary in other view controllers:
- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender
{
ViewController2 *viewController = segue.destinationViewController;
[viewController configureWithSomeState:self.someState];
}
This code assumes that someState is a property defined on ViewController1.
EDIT: One thing you could do--although I do not like this approach because it forces your VCs to have special knowledge about their parent controller--is to derive UINavigationController, then in your storyboard, use the new class for your navigation controller. Store the state in the derived navigation controller and access it from each VC like this:
DerivedNavigationController *navigationController = (DerivedNavigationController *)self.navigationController;
navigationController.someState...;
Typically I'd put information that is used throughout the application in the application delegate where everybody has access to it.
Another possibility is to implement a singleton data management class to hold it for you.
In this case it seems like the application is really a pretty linear flow, so I'd just pass the selection from vc1 to vc2 and then again to vc3 in the respective prepareForSegue calls.
I'm creating an app in Xcode that currently consist of a Navigation Controller a Table View Controller and a regular View Controller.
I'm using StoryBoard and have created a segue between the table view and the regular view controller. In the navigation bar I have a button that I've dragged to the view controller in the StoryBoard. When I click at the button, the new View Controller is viewed like it suppose to. I then tried to pass data from the table view controller, see below:
- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender
{
if ([[segue identifier] isEqualToString:#"läggTill"])
{
// Get reference to the destination view controller
AddPlayerViewController *apv = [segue destinationViewController];
[apv.myTextField setText:#"hello"];
}
}
The segue identifier is "läggTill", but the code inside the if-statement is not executing.
Two questions:
What is wrong with this approach?
Is this the best approach when using StoryBoards? Can I pass data via viewWillDisappear?
Can I use segues to pass data back to the table view controller from the view controller?
It makes all the sense in the world to pass your data in the prepareForSegue:sender:. I would not recommend passing data in viewWillDisappear because it just makes it messy and it reduces readability + it becomes harder to keep track.
I think your string comparison is not working! Put an NSLog for your identifier string see on the console. I have a feeling it might not like the "ä" character in comparison.
About your last question, as Gabriel.Massana pointed out, for passing data back, using delegate is the way to go.
Note 1: Another problem I noticed is a possible typo you might have "apv" and "avc".
Note 2: Another reason for it failing is that you are setting the TextField before viewDidLoad gets called on your destination controller. I suggest that pass it as string and in the viewDidLoad of your destination, set the text to your TextField.
I just have a quick question about recommended ways to implement a master-detail view hierarchy in iOS--the kind where selecting a row in a table on one screen pushes a details view for that item onto the navigation stack.
Specifically, should I reuse the same instance of the details view controller and just change its target and reload it each time, or should I instantiate a new instance of the view controller each time?
I'd prefer the first method, as it just seems generally more efficient, but I'm having trouble figuring out how to set the target and do the reload (especially the first time, when the view controller has not yet even been initialized--I'm using storyboards and that pretty much handles all of the initialization itself).
Or perhaps instead of setting the target on the child view controller, I could set it on the parent, such that each time the child view controller is shown, it reloads itself based on the parent selection? That actually sounds like the best bet so far, just looking for tips/warnings from anyone who's run into this before.
First, there's nothing wrong with creating a new view controller each time. If you use segues, that's what you'll get, since segues always instantiate new controllers. The detail controller will be deallocated when you pop or dismiss it anyway, so it won't persist.
If you want to use the same controller, you have to do your push or presentViewController in code. You can still setup the controller in the storyboard. Give it an identifier, but don't connect it up with a segue. In code, you check for the existence of your controller (you'll need a property for it), and if it doesn't exist, create it.
if (! self.detailController) {
DetailController *dvc = [self.storyboard instantiateViewControllerWithIdentifier:#"MyIdentifier"];
}
self.dvc.whateverProperty = self.somePropertyIWantToPass; // pass some date to it
[self.navigationController pushViewController:dvc animated:YES completion:nil];