I have two view Controllers in my project ViewController, SettingsView. Here I am trying to update the ViewController's label, when i click on the SettingsView's back button. NSLog is working fine, but the label is not updating...
Please help me....
SettingsView.m
-(IBAction)backToMain:(id) sender {
//calling update function from ViewController
ViewController * vc = [[ViewController alloc]init];
[vc updateLabel];
[vc release];
//close the SettingsView
[self dismissModalViewControllerAnimated:YES];
}
ViewController.m
- (void)updateLabel
{
NSLog(#"Iam inside updateLabel");
self.myLabel.text = #"test";
}
Could you please tell me whats wrong with my code? Thank you!
You have to implement protocols for that. Follow this:
1) In SettingView.h define protocol like this
#protocol ViewControllerDelegate
-(void) updateLabel;
#end
2) Define property in .h class and synthesis in .m class..
#property (nonatomic, retain) id <ViewControllerDelegate> viewControllerDelegate;
3) In SettingsView.m IBAction
-(IBAction)backToMain:(id) sender
{
[viewControllerDelegate updateLabel];
}
4) In ViewController.h adopt protocol like this
#interface ViewController<ViewControllerDelegate>
5) In viewController.m include this line in viewDidLoad
settingView.viewControllerDelegate=self
Your label is not updating because , you are trying to call updateLabel method with a new instance.
You should call updateLabel of the original instance of viewcontroller from which you have presented your modal view.
you can use a delegate mechansim or NSNotification to do the same.
Delegate mechnaism would be clean. NSNotification is quick and dirty.
You are not exactly calling the correct vc. This is because you are creating a new instance of that class and calling the updateLabel of that instance.
You have a few options.
Either implement it as a delegate callBack (delegate messagePassing, or delegate notification - however you want to call it) to notify that class instance to call the updateLabel method.
Use the original instance VC as a dependency injection into the class that you are on right now, and use that instance to call the updateLabel
Use NSNotifications / NSUserDefaults to communicate between viewControllers and setup a notification system for your actions. This is quite easy, but not really great in the long run.
I would RECOMMEND option 1 (or) option 2.
Simply declare like this in SettingsView class:
UILabel *lblInSettings;// and synthesize it
Now assign like below when you presenting Settings viewController:
settingsVC.lblInSettings=self.myLabel;
Then whatever you update in lblInSettings it will be present in MainView obviously....
no need for any delegate methods or updating methods.
Means if you assign at the time of dismissing like
lblInSettings.text=#"My new value";
then self.myLabel also will be updated.
Let me know if you have any queries?
Related
I was trying to push a viewcontroller B into navigation controller from A and then assigning some properties of B in A.
In this case, the assigning of properties was done and then viewDidLoad of viewcontroller A was executed.
Here, assigning properties in A should be done only after viewDidLoad of A has done.
For example,
[b.navController pushViewController:a animated:YES];
a.status = #"loaded";
Here, status was assigned first and then viewDidLoad of A was executed.
This happens only in iOS 7 whereas in iOS6 it works fine.
Can anyone please let me know where the problem is?
UPDATE: For me in some cases in iOS7, Push view is not working. How cna I debug and fix it?
Just access the viewcontroller.view (set any thing immediately after the alloc) property after the alloc init;
Which will loadview/viewdidload.
See Apple Documentation
In my experience, a UIViewController view is loaded lazily, no matter which iOS version you're working on. If you want to trigger a view load, and therefore its UIViewController viewDidLoad, you should access the view after the UIViewController is allocated. For example:
UIViewController *aViewController = [[CustomViewController alloc] init];
[aViewController view];
Make sure you don't code it as
aViewController.view
since that would generate a compiler warning.
So, in your case it would have to be something like this:
...
CustomViewController *a = [[CustomViewController alloc] init];
[b.navController pushViewController:a animated:YES];
[a view];
a.status = #"loaded";
Let me know if you have further problems with it.
You can know when a View Controller has been pushed onto the stack by implementing the UINavigationControllerDelegate and setting yourself as the delegate self.navigationController.delegate = self; then you will get this callback after every push
navigationController:didShowViewController:animated:
So you can check if the shown viewController is the one your interested in, then set your a.status.
I would suggest you call a delegate method once the view is loaded.
Set the delegate to be controller B.
and after viewDidLoad finishes (in controller A) call the delegate method. You can even pass parameters as you wish to the delegate.
Here's some example code:
Controller B:
a.delegate = self;
[b.navigationController pushViewController:a animated:YES];
Implement the delegate method:
- (void)controllerIsLoaded:(ControllerA *)controllerA status:(NSString *)status
{
a.status = status;
}
Controller A .h file:
#class ControllerA;
#protocol ControllerADelegate <NSObject>
- (void)controllerIsLoaded:(ControllerA *)controllerA status:(NSString *)status;
#end
#interface ControllerA : UIViewController
#property (nonatomic, weak) id <ControllerADelegate> delegate;
Controller A .m file:
- (void)viewDidLoad:(BOOL)animated
{
[super viewDidLoad:animated];
/* your viewDidLoad code here... */
if ([_delegate respondsToSelector:#selector(controllerIsLoaded:status)])
[_delegate controllerIsLoaded:self status:#"Loaded"];
}
Turn off animation for ios7, in my case its work
[b.navController pushViewController:a animated:NO];
a.status = #"loaded";
No documentation provides enough information to know exactly when viewDidLoad would be called.
UIViewController's documentation just says this
This method is called after the view controller has loaded its view hierarchy into memory
I would suggest that you create a custom initializer like this
- (id)initWithStatus:(NSString *)status {
}
But, if you are trying to use this variable to check if the viewController's view has 'loaded' or not, it may not be possible to do that because the pushViewController or presentViewController methods are not guaranteed to be synchronous.
Even in iOS 6, there was no explicit guarantee that the view would be loaded as soon as that method returned.
Please write the code in viewWillAppear method instead of viewDidLoad in next class i.e. where you are pushing the object to
-(void)viewWillAppear:(BOOL)animated
{
}
I'm understand of your question like this:
B *b = [[B alloc] init];
b.status = #"loaded";
[self.navigationController pushViewController:b animated:Yes];
If you want to pass a value from one controller to another means, you have to assign a value before using pushViewController method.
Noob question fellas, but I cant get it.
I've got a View Controller that loads in a separate View Controller. I would like to be able on a button press to call a method inside the parent View controller. So here is what i've got
parent VC:
.h
-(void)callParentMethod;
.m
-(void)viewDidLoad{
self.childVC.parentVC = self;
}
-(void)callParentMethod{
NSLog(#"Hello?");
}
child VC:
.h
#import "TheParentViewController.h"
#property (nonatomic, weak) TheParentViewController *parentVC;
.m
-(void)addThis{
[self.parentVC callParentMethod];
}
I get no errors, the child VC method addThis seems to call the method, but the NSLog is never called. Any thoughts what i'm doing wrong?
I think parentVC releases because of weak reference. Try to use this method.
-(void)addThis{
NSLog(#"%#", self.parentVC);
[self.parentVC callParentMethod];
}
YourParentVC *parent = (YourParentVC*)[self presentingViewController];
parent.whatever = blah;
I am not quite sure what your application is, but you should not have to keep a reference to the parent view controller. A UIViewController already has a property called parentViewController which you can use in the following way:
[self.parentViewController methodToCall];
This will call a method on the parent view controller. You may need to cast the object in order to call custom methods
[(TheParentController *)self.parentViewController methodToCall];
This of course assumes that the child view controller's view is a subview of the parent view controller view. Hope this helps
Check whether your parent view controller is allocated.
parentnvc = [ParentViewController alloc]initWithNibName:#"somenib" bundle:nil];
if parentvc is allocated and initialised and call the method
You can create a property in child view controller say,
#class ParentVC;
#property(weak,nonatomic)ParentVC *parentVCreference;
and get the reference for the Parent view controller as follows
self.parentVCreference=(ParentVC*)self.parentViewController;
then you can call any exposed methods from ParentVC as follows
[self.parentVCreference parentVCMethod];
Note: You need to import header of ParentVC in ChildVC implementation file.
I have a UIViewController called ShowListViewController that uses a Modal View Controller to push another view onto the stack:
AddShowViewController *addShowViewController = [[AddShowViewController alloc] init];
[addShowViewController setModalTransitionStyle:UIModalTransitionStyleCoverVertical];
[self presentModalViewController:addShowViewController animated:YES];
I would then like to call my method populateTableData of the ShowListViewController class when the addShowViewController disappears.
I would think that the answer found here would work, but it doesn't. My method populateTableData is not detected as an optional method to use.
Essentially my questions is: How do I detect when a Modal View Controller disappears so as to call a method within the class that pushed it on the stack?
This may not be a best solution, but can do what you want at this time.
In your showlistcontroller add an instance variable like
BOOL pushedView;
#implementation ShowListViewController
and before you do the modal presentation set its values as YES like
pushedView = YES;
[self.navigationController presentModalViewController:popView animated:YES];
in the viewWillAppear of ShowListViewController you can detect whether it is appearing because pop getting dismissed or not like
if (pushedView) {
NSLog(#"Do things you would like to on pop dismissal");
pushedView = NO;
}
I think you would like something like this.
You make a delegate inside ur modalVC like this:
#protocol ModalViewDelegate <NSObject>
- (void)didDismissModalView;
#end
and implement it in your MainVC like this:
#interface MainViewController : UIViewController <ModalViewDelegate>
{
Then u will make a delegate property in your modalVC like this:
#interface ModalShizzle : UIViewController
{
id<ModalViewDelegate> dismissDelegate;
}
You set the dismissDelegate of your ModalVC to your MainVC and then you make the delegate method. Before you dismiss it however you will call the ModalVC to do one last thing. (which is populate your table). You will call for the data inside your MainVC and then do whatever you feel like it, just before you dismissed your modalVC.
-(void)didDismissModalView
{
//call ModalVC data here...
//then do something with that data. set it to a property inside this MainVC or call a method with it.
//method/data from modalVC is called here and now u can safely dismiss modalVC
[self dismissModalViewControllerAnimated:YES];
}
Hope it helps ;)
OK so it appears that in Apple's template for Utility App's they ignore what the docs for [UIViewController][1] say and actually go out of their way to call dismissModalViewControllerAnimated: from the UIViewController that pushed the modal view onto screen.
The basic idea in your case will be
Define a protocol for AddShowViewControllerDelegate
Make ShowListViewController implement this protocol
Call a method on the delegate to ask it to dimiss the modal view controller
For a full example just create a new project with Utility template and look at the source for FlipsideViewController and MainViewController
Here is an example adapted for your needs:
AddShowViewController.h
#class AddShowViewController;
#protocol AddShowViewControllerDelegate
- (void)addShowViewControllerDidFinish:(AddShowViewController *)controller;
#end
#interface AddShowViewController : UIViewController
#property (nonatomic, assign) id <AddShowViewControllerDelegate> delegate;
- (IBAction)done:(id)sender;
#end
AddShowViewController.m
- (IBAction)done:(id)sender
{
[self.delegate addShowViewControllerDidFinish:self];
}
ShowListViewController.h
#interface ShowListViewController : UIViewController <AddShowViewControllerDelegate>
{
...
}
ShowListViewController.m
- (void)addShowViewControllerDidFinish:(AddShowViewController *)controller
{
[self dismissModalViewControllerAnimated:YES];
[self populateTableData];
}
I'm trying to send an array from one viewController to another using protocols and delegates. I declared the delegate on viewcontroller B and used the following code in viewcontroller A to send the message from A to B. The protocol's method is didReceiveMessage. Unfortunately, the message never arrives.
Attached is the code from viewController A
- (IBAction) graphPressed:(UIButton *)sender {
GraphingViewController *gvc=[[GraphingViewController alloc] initWithNibName:nil bundle:nil];
[self presentModalViewController:gvc animated:YES];
[gvc release];
[delegate didReceiveMessage:brain.internalExpression];
}
and the code from viewcontrollerB
- (IBAction) ViewdidLoad {
CalculatorViewController *cvc =[[CalculatorViewController alloc] init];
cvc.delegate=self;
[cvc release];
}
- (void) didReceiveMessage:(NSMutableArray *)expression {
NSLog(#"message received from CalculatorAppDelegate");
}
Any suggestions would be greatly appreciated.
I'm not sure what are you doing in second sample? You created an object, assign its delegate property and then released it. Why?
If that is code from your application it could probably be from releasing cvc at the end of your ViewDidLoad method.
init would give it a retain count of 1, and the release would take it back to 0.
Also the code seems sort of backwards, if you wanted to set view A as the delegate for view B, you would do so in view A.
Unless there is a more complex reason to use a delegate that I'm not seeing from the code, I would just keep a pointer around to the child if you really need to send it messages.
Like others have posted, you are just getting rid of the Calculator VC after creating it. I would recommend adding an #property to the second VC and using it to store a pointer to the Calculator. It should be a retain property. Then set the delegate of that property to self.
Also, you make sure to use an assign property for the delegate value, and try to use the property syntax (self.delegate) whenever possible.
There could absolutely be more going on here, so if this doesn't actually solve the problem try and post up more of your code (header files, what connections are made in IB, etc.)
Edit: For the record, the method is -(void)viewDidLoad, not -(void)ViewDidLoad, so that could be contributing to the problem.
As you said you are trying to pass an array from one view controller to another.Well i use in this way.Here is the code
- (IBAction) graphPressed:(UIButton *)sender {
GraphingViewController *gvc=[[GraphingViewController alloc] initWithNibName:nil bundle:nil];
gvc.myArray=infoArray;
[self presentModalViewController:gvc animated:YES];
[gvc release];
}
Where myArray is array in your GraphingViewController,You just need to make property of this array with retain attribute,simply as
#property(nonatomic,retain)NSMutableArray *myArray;
And you need to Synthesize it as well.
I'm trying to figure out how I can call a function from another one of my classes. I'm using a RootViewController to setup one of my views as lets say AnotherViewController
So in my AnotherViewController im going to add in on the .h file
#class RootViewController
And in the .m file im going to import the View
#import "RootViewController.h"
I have a function called:
-(void)toggleView {
//do something }
And then in my AnotherViewController I have a button assigned out as:
-(void)buttonAction {
//}
In the buttonAction I would like to be able to call the function toggleView in my RootViewController.
Can someone clarify on how I do this.
I've tried adding this is my buttonAction:
RootViewController * returnRootObject = [[RootViewController alloc] init];
[returnRootObject toggleView];
But I dont think that's right.
You'll want to create a delegate variable in your AnotherViewController, and when you initialize it from RootViewController, set the instance of RootViewController as AnotherViewController's delegate.
To do this, add an instance variable to AnotherViewController: "id delegate;". Then, add two methods to AnotherViewController:
- (id)delegate {
return delegate;
}
- (void)setDelegate:(id)newDelegate {
delegate = newDelegate;
}
Finally, in RootViewController, wherever AnotherViewController is initialized, do
[anotherViewControllerInstance setDelegate:self];
Then, when you want to execute toggleView, do
[delegate toggleView];
Alternatively, you could make your RootViewController a singleton, but the delegate method is certainly better practice. I also want to note that the method I just told you about was Objective-C 1.0-based. Objective-C 2.0 has some new property things, however when I was learning Obj-C this confused me a lot. I would get 1.0 down pat before looking at properties (this way you'll understand what they do first, they basically just automatically make getters and setters).
I tried out the NSNotificationCentre - Works like a charm - Thanks for your reply. I couldn't get it running but the NS has got it bang on.
[[NSNotificationCenter defaultCenter] postNotificationName:#"switchView" object: nil];