In my iOS app setup, I have a universal object (lets call it UniversalObj) declared in the top level object. (SampleAppDelegate in my case)
Within this, I have a UITabBarController containing two UIViewController (which I want to have access to UniversalObj.
In SampleAppDelegate, I have tried the following to pass UniversalObj to it:
MyViewController *vc = (MyViewController *) [self.tabBarController.viewControllers.objectAtIndex:0];
[vc setMyObj:self.universalObject];
The problem with this is that when I do this, sometimes, the view hasn't loaded yet so MyViewController.myObj==null.
Now, I am trying to access SampleAppDelegate (of type NSObject) from MyViewController. I can get to the UITabBarController using: ***self.parentViewController***, but I don't know how to get to SampleAppDelegate.
How can I access UniversalObj in SampleAppDelegate from MyViewController? How can I change the self.parentViewController line in MyViewController to get to SampleAppDelegate? Or is there a better way to do this?
Thanks in advance for your help.
Guvvy
You would use -[UINib instantiateWithOwner:options:]:
NSArray * topLevelObjects = [nib instantiateWithOwner:pwner options:options];
I found that I was able to access the object from MyViewController like this:
[self setMyObj:[(SampleAppDelegate *)[UIApplication sharedApplication].delegate universalObj]];
Related
SettingsStore.h
#interface SettingsStore : IASKAbstractSettingsStore
{
#public
NSDictionary *dict;
NSDictionary *changedDict;
}
- (void)removeAccount;
#end
menuView.m
-(IBAction)onSignOutClick:(id)sender
{
SettingsStore *foo = [[SettingsStore alloc]init];
[foo removeAccount];
[self.navigationController pushViewController:foo animated:YES];
exit(0);
}
I want to call this removeAccount function from menuView.m. But I am getting error.
How to fix it and call this removeAccount.
There are few mistakes in your Code please find them below.
[foo removeAccount]; Calling this method is correct
[self.navigationController pushViewController:foo animated:YES];
Not correct because SettingsStore is not subclass of
UIViewController only subclass of UIViewController can be pushed to
Navigation controller
exit(0); Calling this method is not
recommended by Apple
You are calling removeAccount correctly from your menuView.m file, but there are several issues with your code:
You are treating foo as though it were a UIViewController, and it's actually a member of the SettingStore class. Does the SettingStore class refer to an actual screen, or is it more a data object (for storing settings?). If it's the latter, you don't want to push it on. You can create it, and use it, but the user doesn't need to see it.
You are calling exit(0); you can remove that line. If you want to remove the menuView.m file from your memory, remove references to it (e.g. from its parent view controller).
The menuView.m file is confusing, as in, is it a view or a viewController. An IBAction I would normally stick in a ViewController file, rather than a view file. Your basic design pattern is MVC (Model / View / Controller). In this case, it seems your SettingStore file is a Model (data), the menuView.m is a View and your code is for the Controller bit.
This question already has answers here:
Passing data between view controllers
(45 answers)
Closed 7 years ago.
I need to pass data between two ViewControllers but without UIButton, in a few words, I need to access a variable which is in other ViewController.
My code is:
LoginViewController *lvc;
NSString name=lvc.name;
This specific case might be a little easier than delegates.
From what I see, you're trying to pass login credentials (name/login/password/something). I would use two things depending on the actual matter here.
Either NSUserDefaults or -performSegueWithIdentifier:
NSUserDefaults is a file that is loaded in every app that you can read and edit, simply using the following commands :
Setting a variable :
NSString *aName;
[[NSUserDefaults standardUserDefaults]setObject:aName forKey:#"userName"];
Getting a variable :
NSString *aName = [[NSUserDefaults standardUserDefaults]objectForKey:#"userName"];
Note that you can save the following objects NSDictionary, NSArray, NSString, NSNumber, NSData, and probably a couple that I'm forgetting but someone can edit if I do.
Note that this file is loaded at every startup, so you don't wanna use that as a database but more of a small-sized storage easy to use, like for user name, preferences/settings, and stuff like that.
The other way is using performsegue between two controllers, but that requires storyboards.
Drag a segue between two of your controllers, name it (for example) fromLoginToHome. I'm assuming that the flow goes from the login controller to the home controller.
when you move between the two views (when the user presses "Login" for example), call this method
[self performSegueWithidentifier:#"fromLoginToHome" sender:self];
Then you'll need to implement this method, that is usually there but in a comment block (it's always like that when you create your Vc)
- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender {
if([segue.identifier isEqualToString:#"fromLoginToHome"]){
HomeViewController *vc = (HomeViewController*)segue.destinationViewController;
vc.myName = _myName;
}
}
Xcode using delegate to pass data between controllers This is for child to parent by usuing delegates
And For parent to child,you can use segues simply.
HTH!enjoy Coding.
You can have a look of delegate method in here delegate. can you tell me if you are looking for delegate or not
Try using as below
FirstViewController.h
#interface FirstViewController: UIViewController
- (void)GetItNow;
FirstViewController.m
- (void)GetItNow{
NSLog(#"I acheived"); }
- (IBAction)goToSecondView:(id)sender {
SecondViewController* Second= [[SecondViewControlleralloc] initWithNibName:#"SecondViewController" bundle:nil];
rqVC.addId = self.addId;
[self.view addSubview:Second.view];
}
SecondViewController.h
#property (nonatomic, assign) id delegate;
SecondViewController.m
- (IBAction)Action_LoadFunds:(id)sender {
[self.view removeFromSuperview];
[_delegate GetItNow];
}
I am making master detail application, i have dynamic Detail ViewController. Detail ViewController are changed.
But in every Detail ViewController I have one common method updateInfo I want to call that method
Here is my code
UINavigationController *nav=[self.splitViewController.viewControllers objectAtIndex:1];
UIViewController *controller=[nav.viewControllers objectAtIndex:0];
[controller updateLastInfo];
But it gives me error no method found.
it will work if i use UIViewController name.
HomeViewController *controller=(HomeViewController)[nav.viewControllers objectAtIndex:0];
[controller updateLastInfo];
But i dnt want to do above things.
I have tried to explain. Please help
You can use id
UINavigationController *nav=[self.splitViewController.viewControllers objectAtIndex:1];
id controller=[nav.viewControllers objectAtIndex:0];
[controller updateLastInfo];
You could subclass UIViewController and make a base DetailViewController class that houses common functionality of your detail view controllers. Then you would make all of your detail view controllers subclass DetailViewController instead of UIViewController. This would be a safe way to do it and would also allow you to add extra functionality to your updateInfo method in the specific detail view controllers.
If you want an unsafe way, you could make your controller object of type id. I wouldn't suggest this approach as it relies on your personal knowledge of the code. If someone else (or yourself down the road) sets it to a view controller that doesn't have that method, the code will still try to run and will crash.
UIViewController doesn't have a method named updateInfo, so the compiler will of course complain when you try to send that message to a pointer that's known only to point to an instance of UIViewController. When you use the class name, like this:
HomeViewController *controller=(HomeViewController)[nav.viewControllers objectAtIndex:0];
you're providing more information to the compiler, using a type cast to tell it "Hey, don't worry, I know for certain that the object I'll get back is a HomeViewController. Since you seem to have several types of view controllers that all have this method, the best thing to do is to declare the updateInfo method in a protocol and then have each of those UIViewController subclasses implement that protocol. So, your protocol declaration would be in a header file and might look like:
#protocol SomeProtocol
- (void)updateInfo
#end
and each class that has an -updateInfo method would just need to declare that it adopts the protocol:
#interface HomeViewController <SomeProtocol>
//...
#end
and then make sure that you have an -updateInfo in your class implementation:
#implementation HomeViewController
- (void)updateInfo {
//...
}
//...
#end
Then, in your code, you can either check that the object conforms to the protocol using -conformsToProtocol: like this:
if ([controller conformsToProtocol:#protocol(SomeProtocol)]) {
UIViewController<SomeProtocol> *c = (UIViewController<SomeProtocol>*)controller;
[c updateInfo];
}
or else just check that the object responds to the selector before calling it:
if ([controller respondsToSelector:#selector(updateInfo)]) {
[controller performSelector(updateInfo)];
}
The other answers you've received (using id or creating a common base class) are also good ones, but to be safe make sure you do some checking before calling your method. For example, you can use -isKindOfClass to make sure that the view controller you get back is in fact an instance of your common base class, and you can use -respondsToSelector: as above to check that an id points to an object that implements updateInfo.
iI'm very new in programming with multiple view controllers.
I have a RootViewController, and a FirstViewController. Inside RootViewController:
#property (nonatomic, retain) FirstController * firstController;
- (FirstController *)firstController {
if (!_firstController) {
UIStoryboard *storyboard = self.storyboard;
_firstController = [storyboard instantiateViewControllerWithIdentifier:#"First View"];
}
return _firstController;
}
So, I manage to see the FirstViewController that I've designed in the storyboard.
The problem is this. If I try to run this instruction inside RootViewController:
_firstController.myString = _myString;
myString is obviously the name of a property inside RootViewController and the same inside FirstViewController. Running this instruction doesn't work without allocating memory for _firstController. But, if I allocate memory and initialize _firstController, every adjustments made in the Interface Builder will be vanished.
How can I solve? I'm sure I'm trying to do something very wrong.
Thank you in advance.
You wrote getter - so use it!
self.firstController.myString = _myString;
instead of
_firstController.myString = _myString;
You're trying to access instance directly and of course there are no memory allocated for it because you are using technique called 'lazy loading'(ivar will be allocated when it needed.) By using self.firstController you simply send message [self firstController] which will allocate memory for first controller.
I have the following setup in my app:
A UITabbarController with 3 viewcontrollers, with embeded UINavigationControllers.
The 3 viewcontrollers inheret/superclass from a UIViewController subclass called "SVC", in order to implement elements which is used in all of the 3. viewcontrollers and prevent duplicated code. In this "SVC" class I have setup a delegate called "dismissDelegate" (which is used to tell when the tabbarcontroller is dimissed).
#protocol ModalViewDelegate <NSObject>
- (void)didDismissModalViewFrom:(UIViewController *)viewController;
#end
#property (weak, nonatomic) id <ModalViewDelegate> dismissDelegate;
My other viewcontroller which segues to the UITabbarController, implements this delegate in order to get information about, when the tabbarcontroller is dismissed.
the SVC class notifies the delegate of dismissal of the tabbar like so:
[self.dismissDelegate didDismissModalViewFrom:self];
I now want to set the delegate of all the viewcontrollers which inherts from the SVC class (all the tabbar viewcontrollers) to this viewcontroller and I try to do this via the prepareToSegue method like so:
- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender
{
if ([[segue identifier] isEqualToString:#"ToTab"]) {
UITabBarController *tabBarController = segue.destinationViewController;
for (UINavigationController *navController in tabBarController.viewControllers) {
for (UIViewController *vc in navController.viewControllers) {
_SubclassVC = (SVC *) vc.superclass;
_SubclassVC.dismissDelegate = self;
}
}
}
}
But I get the following error:
+[SVC setDismissDelegate:]: unrecognized selector sent to class 0xbca68
My questions:
Is this the right way to tackle this senario (get information about dismissal of a viewcontroller and setup this delegate in a subclass which is inhereted by multiple viewcontrollers)?
How do I manage to set my first viewcontroller as the delegate of all the viewcontrollers in the tabbar - the SVC class, so I can get notified when the tabbarcontroller is dimissed and solve the error?
+[SVC setDismissDelegate:]: unrecognized selector sent to class 0xbca68
See the +
The plus sign idicates that you are calling a class method. You must have tried setting a class variable by a setter. But a property represents instance variables only. Therefore the setters and getters that are automatically generated are intance methods only. (starting with a minus - in error messages like this).
And that is what you do:
_SubclassVC = (SVC *) vc.superclass;
_SubclassVC.dismissDelegate = self;
For whatever reason (probably by mistake or misunderstanding) you take the vc instance and get its superclass. vc.superclass returns a class object, not an object (meaning not an instance, in Obj-C class objects are objects too).
Then you typecast it to (SVC *) just to stop the compiler from throwing errors (or warnings - not sure).
Well, I guess that you wondered yourself why you have to typecast it at all. That's the reason :)
Next, you assign self to a property dismissDelegate. The compiler does that because you typecasted it to SVC* which does have a property dismissDelegate. The compiler will actually call the setter setDismissDelegate as usual in contructs like this.
BUT at runtime the message (or selector) setDismissDelegate: is not sent to an SVC* but to a class object. And the class SVC does not have a method (or selector) +setDismissDelegate: and therefore cannot resolve the message. And that is exactly what the error message is telling you.
All right, now we get to your questions.
1. Well, it is not the way I would do it, but that is certainly one way of achiving it.
2. If you want to stick with that unusual approach then do this minor change and you will get rid of the error:
for (SVC *vc in navController.viewControllers) {
vc.dismissDelegate = self;
}
There is no point in fetching the superclass object. If you cannot access the property of a superclass then you did something wrong with the inheritance chain.
If you want to be on the save side:
for (UIViewController *vc in navController.viewControllers) {
if (vc isKindOfClass:[SVC class]){ //BTW, this is good usage of the class object
SVC *svc = (SVC*) vc;
svc.dismissDelegate = self;
}
}