Let's say I have a view controller called vc1, which a synthesized property called property1, and i wants to access it from another view controller (vc2) and change it from vc2.
Now the methods created by the #syntisize to change and get properties are instance methods, so how can I get to them fro another view controller (do view controllers have instances in the app, and if so, what are they?)
Just to be clear I am using storyboards, so I never really instantiate the view controllers...
VC1.m:
-(void) yourMethod {
...
}
VC2.m
YOURViewController * vc2 = [[YOURViewController alloc]init];
[vc yourMethod];
[vc release];
Make sure to import your YOURViewController in your other view .m file
Something like that should work.
Or if you're having problems, try this tutorial here:
Tutorial on How-To Pass Data Between Two View Controllers
Hope this helps :)
While you can do it the way you describe, I think the common technique (assuming VC1 has a segue to VC2) is a bit different, where VC2 will have a property that will be set by prepareForSegue. See Configuring the Destination Controller When a Segue is Triggered in the View Controller Programming Guide.
You will need to link the storyboard views with the viewcontrollers so the view for vc1 would use the class vc1 etc for the rest (I assume you have done this because this is important when coding for different views)
Then all you need to do is where ever you are calling the properties so lets say the viewDidLoad method, declare the view controller like this:
- (void) viewDidLoad {
vc1 *viewController;
// Now you change the variable I'll presume its a UILabel so I'll change its text [viewController.property1 setText:#"I changed a different views UILabel"];
}
Let me know whether this works... Its worked for me before so should work
Related
I am trying to push a view controller to the screen. The push is successful but when I later try to access any property of the pushed view controller including textboxes and labels, they are all nil.
How do I avoid this?
I am doing it this way because I need my code to decide which view controller to push. Any help is much appreciated.
myVC *vC = [self.storyboard instantiateViewControllerWithIdentifier:#"myVC"];
[self.navigationController pushViewController:vC animated:YES];
After the code you've wrote, you will need to either approach your properties like this:
vC.property = assignedValue;
Make sure you have synthesized your properties, or initialised them with a setter in the vC's viewDidLoad
If you are using Storyboard , You can actually use prepareForSegue for transferring data between ViewControllers.
And be sure your properties are declared in .h file. You can't access .m file properties.
Hope this helps.
I am looking to replace the back button in the UINavigationController throughout my application. My requirements is that this back button be defined in one XIB and if possible, the code to set it is in one place.
I have seen various methods that set the property self.navigationItem.backBarButtonItem to be a UIBarButtomItem with the custom button as it's view, e.g. [[UIBarButtonItem alloc] initWithCustomView:myButton];
My first thought was to create a global category (not sure if that's the term, I'm new to Objective-C as you might have guessed) that implements 'ViewDidLoad' for all my UINavigationControllers, and setting this property. My problem is loading the XIB to this button that I create at runtime.
Does anyone have a suggestion on a neat way of doing this (I guess it must be a common thing to do, and I can't imagine repeating code in all my screens). I have considered creating a UINavigationController subclass, however I wasn't sure how this would effect my custom implementations of ViewDidLoad.
Any advice much appreciated. Also I need to target >= iOS4 (the appearance API is iOS5 only).
I prefer to not force inheritance where possible so you could do this with two categories
#interface UIViewController (backButtonAdditions)
- (void)ps_addBackbutton;
#end
#implementation UIViewController (backButtonAdditions)
- (void)ps_addBackbutton;
{
// add back button
}
#end
#interface UINavigationController (backButtonAdditions)
- (void)ps_pushViewController:(UIViewController *)viewController animated:(BOOL)animated;
#end
#implementation UINavigationController (backButtonAdditions)
- (void)ps_pushViewController:(UIViewController *)viewController animated:(BOOL)animated;
{
[viewController ps_addBackbutton];
[self pushViewController:viewController animated:animated];
}
#end
Now #import these files as appropriate and instead of using
[self.navigationController pushViewController:aViewController YES];
use
[self.navigationController ps_pushViewController:aViewController YES];
Disclaimer
I free styled this in the browser so you may need to tweak it
I had the same issue in my current project, the solution I came up with was to create a MYBaseViewController base class without xib and there in viewDidLoad programmatically (if you want to init barButtonItem with custom view, you are not able to create in xib anyways) create a customBackButton (and of course release it and set to nil viewDidUnload.
This works good for me because this way I can create xibs for all my other viewControllers that are subclasses of MYBaseViewController(if you created a view for base class in nib you would not be able to create a nib for a subclass).
I have a view based app (not navigation or tab based...)
My main view controller is called from the app delegate and initiated from a xib.
Then I use presentModalViewController to bring another view on the screen with it's own xib and view controller.
I have no problems passing data to that view controller.
However, when I dismiss the second view controller, I want to send data back to the main view controller for my app, but I just can't figure out how to reference it. Actually, I'd like to call a method in the main view controller if possible.
I've been struggling with this a bit and have found suggestions online but I just can't seem to get it to work. I'm hoping someone can provide the sample code to do this.
P.s. is this "main view controller" still referred to as a "root view controller" or is that term only used when dealing with a view controller stack (i.e. navigation or tab view controller)
EDIT:
I'm sure Bryan's solution would work so I have accepted as answer. However I ended up using NSNotificationCenter to get this to work and I find it a bit simpler to understand as a beginner
You can use the delegation pattern. In your modal view controller's header file, create an interface for a new delegate protocol...
#protocol ModalViewControllerDelegate <NSObject>
- (void)sendData:(Data *)someData;
#end
...and give your ModalViewController a new instance variable that implements this protocol:
#property (nonatomic, assign) id<ModalViewControllerDelegate> delegate;
Your main view controller should implement this protocol...
#interface MainViewController : UIViewController <ModalViewControllerDelegate> {
...and set itself as the delegate before it presents the modal view controller:
ModalViewController *modalViewController = [[[ModalViewController alloc] init] autorelease];
[modalViewController setDelegate:self];
// Present modal view controller
The main view controller should implement the delegate protocol's method:
- (void)sendData:(Data *)someData {
NSLog("I have just received some data: %#", someData);
}
Then inside your modal view controller, you can simply call the following method whenever you want to send data back to the main view controller:
[delegate sendData:someData];
I might be confused here and asking the wrong question.
If I use a class like the UISplitViewController inside the appdelete.m, will the only message i will receive is the message the UISplitViewController calls and not any VIEW message? for example:
in my myappdelegate.m
....
UISplitViewController *mySplitViewController = [[UISplitViewController alloc] init];
mySplitViewController.viewControllers = [NSArray arrayWithObjects:leftside,rightside,nil];
...
mySplitViewController.delegate = self;
....
[windows addSubView:mySplitViewController.view];
....
-(void) viewWillAppear:(BOOL) animated {
}
in myappdelegate.h I included UISplitViewControllerDelegate
I expected viewWillAppear to fire but it is not. I assume if I had subclass UISplitViewControler it would have fire. right?
BTW: I am doing this without using IB. Do I need to set the target for the mySplitViewController?
What I want to do is setup the orientation of the splitviewcontroller when it rotates.
the viewWillAppear method and other view related methods will be called on the view or view controller themselves, not on the delegate.
That means that if you make a subclass of UISplitViewController called SplitViewControllerSubClass, the view... methods will be called on the instance of SplitViewControllerSubClass, not on the delegate object.
But considering you are creating the views and displaying them programmatically, you already know exactly when the view will appear (i.e., right before you add it to the window), so I believe you could do whatever setup you want at that point.
I found this code to display a modal view:
- (void)add:(id)sender {
// Create the root view controller for the navigation controller
// The new view controller configures a Cancel and Done button for the
// navigation bar.
RecipeAddViewController *addController = [[RecipeAddViewController alloc]
initWithNibName:#"RecipeAddView" bundle:nil];
addController.delegate = self;
// Create the navigation controller and present it modally.
UINavigationController *navigationController = [[UINavigationController alloc]
initWithRootViewController:addController];
[self presentModalViewController:navigationController animated:YES];
// The navigation controller is now owned by the current view controller
// and the root view controller is owned by the navigation controller,
// so both objects should be released to prevent over-retention.
[navigationController release];
[addController release];
}
My question is how do I implement this code (I'm going to place it in a buttonPress method)
Do I need to define anything in my header file? The bit that confuses me is that apple on provides this and no header file so i cant tell if anything should be there?
The code refers to RecipieAddViewController what do I repleace this with, "UIViewController" ?
What do I put as the delegate in the headerfile ? do I need to set this up anywhere else ? like with a property?
Is there anything else I need to do once I have copid this code in my buttonPress method to make it work?
Thanks and sorry for all the questions.
My question is how do I implement this code (I'm going to place it in a buttonPress method)
Define the method as an IBAction like -(IBAction)add:(id)sender and in interface builder bind a button's touch up inside event to the view controller object's add: action outlet.
Do I need to define anything in my header file? The bit that confuses me is that apple on provides this and no header file so i cant tell if anything should be there?
Nope. All this stuff needs is UIKit.h You usually need to change your header to add methods, add instance variables, or include custom classes. You may need a #import RecipeAddViewController.h somewhere (in your header or your implementation file) in order to use that class, however. This is true for any custom class you write that you want to use in another file.
The code refers to RecipieAddViewController what do I repleace this with, "UIViewController"?
Replace that with the view controller class you want to push. UIViewController itself is rarely useful naked. It's made to subclassed. So you create a new class that inherits from UIViewController, import it's header, create and instance of it, and push it on the navigation controller.