I know this has been asked, but I can't figure out how to make this work with my app -- I'm sure I'm doing it wrong.
I have two view controllers embedded inside a UITabBarViewContoller, FirstViewController and SecondViewController. SecondViewController is nothing more then a few UITextFields for managing a hostname and port that the app connects to.
FirstViewController contains most of the code (which I know isn't very MVC oriented). I'm trying to implement Delegation from SecondViewController back to FirstViewController (Passing Data between View Controllers) but it seems like my delegate methods aren't being called. Since this is based on storyboards, I'm not creating the instance of SecondViewController and I'm not sure how to set the Delegate. Is there a way to access the instance of SecondViewController so I can set the Delegate?
milesper thank you!
My solution (in swift)
let secondView = self.tabBarController.viewControllers[1] as SecondViewController
secondView.delegate = self
Related
I have a tab bar controller and a few other viewcontrollers outside the tab bar controller. I have this viewcontroller called "X" which is a part of the tab bar controller. I have another viewcontroller called "Y" which is not a part of the tab bar controller. Now i want to initiate X when im inside Y upon tapping a button without actually presenting it. I want X to become active and fire its viewdidload so that i can access X whenever i chose to do so. Is this possible. Im sorry if im not clear in explaining my quiestion. let me know if you need any other additional information.
Old question at this point, but I was looking for an answer myself just yesterday and managed to get it figured out.
Instantiate the ViewController, then call loadViewIfNeeded().
Example:
let storyboard = UIStoryboard(name: "Main", bundle: nil)
let exampleVC = storyboard.instantiateViewController(withIdentifier: "ExampleViewController") as! ExampleViewController
exampleVC.loadViewIfNeeded()
If you want, you can then check if the view is loaded with:
exampleVC.isViewLoaded
The ViewController is now all set up and ready for display when you decide to present it.
I want X to become active and fire its viewdidload so that i can access X whenever i chose to do so.
UIViewController uses lazy loading for the view property. You can just call:
[myViewController view];
This will trigger the loadView and/or viewDidLoad methods, if implemented.
However, you may wish to consider moving the relevant logic from viewDidLoad to init (or initWithCoder: if using a storyboard/xib). This way you won't have to call -view.
If I understand right, you want X to be initialised. So you can perform all you initialisation actions on your init constructor. viewDidLoad will only be called by the framework when you perform some presentation, either by pushViewController or addSubview. The reason for that is that because the framework wants to avoid getting instances of views on the memory without being used. So you can initialise all you want from your controllers but the views won't be loaded.
I have problem with calling methods from one UIViewController by another UIViewController.
Currently I have UIScroll view with two UIViewControllers.
I want to change something in second one and see results in first one.
I try to do this in this way:
Inside function of second UIViewController:
-(void)doSomething:(){
FirsOneViewController *firstVC = [FirsOneViewController alloc] init];
[firstVC changeUnits:0];
}
Function is called but I don't se any changes in first controller.
BR,
Paul
From your code I see you create a new instance of FirstViewController and so there is no reason why the current instance inside the scrollview would receive this message.
You need to send the changeUnits: message to the current FirstViewController, so you need a reference to it. To do this you may want to think about creating a protocol, so that you parent container (the scrollview) is notified by the SecondViewController and then notifies the FirstViewController. A simpler(and lazier) solution is make the SecondViewController have a strong reference to the FirstViewController (though this solution may bite you in the future).
As said in other answers you are creating a new instance of FirsOneViewController instead of referencing to the one you already have.
Here are three ways of doing what you are asking:
Delegation:
The FirstViewController should be the delegate of the SecondViewController (as the secondViewController is calling methods on the FirstViewController). You should tell the SecondViewController that the FirstViewController is its delegate in what ever class initialises the two viewControllers.
From what you have said so far this seems like your best option.
NSNotification:
This could be good option if you think more than one object will want to listen to the change in the SecondViewController. Just post an NSNotification in the SecondViewController and add an NSNotification listener in the FirstViewController
Singleton:
if there should only ever be one instance of the FirstViewController in existence then make it a singleton. By making a class initialiser method. so that you can create/get the current instance of the object from anywhere in your appellation.
Hope this helped.
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 accidentally assigned the same custom class to two UIViewControllers in Storyboard:
#interface SecondViewController : UIViewController
With this the app ran properly. But when I change the custom class for the second View Controller from FirstViewController to SecondViewController the app crashes when the second View Controller loads. How do I rectify this situation?
More information is definitely needed here. However, one of the things to look for is that if you are using the FirstViewController class in code somewhere (in -prepareForSegue for the presenting UIViewController for instance), you'll need to make sure to change that code so that it's using the proper pointer for the class when referencing the SecondViewController class.
For instance, if you do the following and the destinationViewController is of class SecondViewController, then you will get a crash:
FirstViewController *firstView = (FirstViewController *)[segue destinationViewController];
If you could post the presenting class and the FirstViewController and SecondViewController classes, then we can provide more information.
This is embarrassingly obvious now, but I found the problem arose from a button being linked to an IBAction in the the FirstViewController class. When the app was run it crashed because of the improper link.
I may go mad very soon.
This is the reason:
- I started up with Single View Application project with storyboards. Then I set the view controller class name in the storyboard for my viewController.
- Next step I created one pointer for this viewController in AppDelegate method ...didFinishLaunchingWithOpt... and filled it up by calling [myStoryboards instantiate...]. It works pretty good because I can call method like [vc1 setMyName] which does smthng like self.myName = #"Johnny";
- But here it comes. When I create IBAction method joined with button, this method doesn't know anything about "Johhny". And this is because I'm in another instance. When I check the address of "self" it is another one...
WhyWhyWhy??? Please help, how can I use still the same object - the one instantiated in AppDelegate by storyboards and the one from storyboards in "interface builder".
Thank you.
Oh my. I think I really underestamated it...
When we were talking about getting pointer of other viewControllers from storyboard...
I have initialViewController got by calling rootViewContr... And another one connected with segue (modal) where is UITableView. A get data on rootViewController and I want to show them on the other one in the list (UITableView). So I call segue (performSegueWithIdentifier), the other controller is shown but the list is clear. Because the method I call is working with tableView variable which is null :/ Because, again, I'm in another object. That is because I call that method storyboard instantiate... How can I get exactly the same viewController which I'm working in storyboard with. It is quite confusing for me :/
I read something about prepareForSegue and getting the pointer by destinationViewController but that is not what exactly I want. I need the pointer before I call segue method and the viewController is shown...
Thank you.
If you've set up your initial view controller properly in the storyboard, you don't need to assign it to the windows rootViewController property in -applicationDidFinishLaunchingWithOptions: as this is done for you automatically. It sounds like you're creating a second instance. To access the original instance setup by the storyboard simply do this in -applicationDidFinishLaunchingWithOptions:
InitialViewController *viewController = (InitialViewController *)self.window.rootViewController;
viewController.myName = #"Johnny";