iOS: call method from a separate viewController - ios

In my main view controller, I have a button that calls a popover. Since the popover has it's own view controller, its buttons call methods in the popover's view controller. But how would I call a method from the main view controller?
I tried this. In the popover view controller I added a property in the .h
#class ViewController;
#interface PopoverContent : UIViewController <UITextFieldDelegate>
...
#property (strong, nonatomic) ViewController *parentView;
In my popover implementation I did this in viewDidLoad:
self.parentView = [[ViewController alloc] initWithNibName:nil bundle:nil];
In ViewController I have a method called generateHash so I tried
[parentView generateHash];
But I get the error:
No visible #interface for 'ViewController' declares selector 'generateHash'
Any idea what I'm doing wrong? Thanks

remove this line, don't want to create a new instance of view controller
self.parentView = [[ViewController alloc] initWithNibName:nil bundle:nil];
change this line
#property (strong, nonatomic) ViewController *parentView;
to this, so your parent view pointer is of the right class type
#property (weak) ParentView *parentView;
now inside parent views .m file
- (void) createPopup
{
PopoverView *popoverV = [[PopoverView alloc] init];
popoverV.parentView = self;
//And some command to show your popup, addSubview, or presentModal, or whatever
}
Then in PopoverView.m file, you can call methods of the parentView like so
[self.parentView SomeMethod];

This is a good place to use a delegate protocol. In the PopoverContent.h, add something like this:
#protocol PopoverContentDelegate : NSObject
- (void) method1;
#end
Naturally, you can have more than one method, and the method(s) can return values and take parameters like any other method. Also, in the same file, add property called delegate. (Technically, it can be called anything, but everyone who looks at your code will know exactly what you're doing if you call it delegate.)
#interface PopoverContent
#property (weak) id<PopoverContentDelegate > delegate;
//other properties and methods
#end
Finally, in your "main" view controller's .m file, import PopoverContent.h file and set the delegate to self. Also implement method1 to do whatever you need it to do.
//Create the view controller
myPopoverContentController.delegate = self;
//Create the popover with the view controller.
Now, in PopoverContent controller, you can call method1 on the delegate wherever you need to.
[delegate method1];

First, to answer your question, you probably have to define the generateHash method in your ViewController.h file.
Second, I'd suggest that your design approach is not optimal. The generateHash method probably needs to be in another file that can be called from both your ViewController and Popover content controller. For example consider another objective-c .h/.m pair "MyHashMethods":
MyHashMethods.h
+ (void)generateHash;
MyHashMethods.m
+ (void) generateHash
{
// hash code
}
This would allow you to just include MyHashMethods.h in whatever view controllers you need and then call
[MyHashMethods generateHash];
when you need it.

Related

.delegate self unrecognized selector sent to instance

I've a TableViewController in which I'm saving the selected cells in an NSMUtableArray. After selecting these cells user clicks on a confirm button and in this button action I'm trying to pass that NSMUtableArray so that I can display it in another viewController tableView
#import <UIKit/UIKit.h>
#protocol SelectedDXDelegate;
#interface AddDXTableViewController : UITableViewController
#property (nonatomic, strong) NSMutableArray *favDXArray;
#property (strong, nonatomic) UISearchController *searchController;
#property (nonatomic, strong) DX *AddEditDX;
#property (weak) id<SelectedDXDelegate> delegate;
- (IBAction)confirmPressed:(id)sender;
#end
#protocol SelectedDXDelegate <NSObject>
#required
-(void)getSelectedDX:(NSMutableArray *)DXselected;
#end
So when confirm button is pressed
- (IBAction)confirmPressed:(id)sender {
[self.delegate getSelectedDX:selectedDX];
[self.navigationController popViewControllerAnimated:YES];
}
it gets me to the
-(void)getSelectedDX:(NSMutableArray *)DXselected
{
myDXSelected = DXselected;
}
But it crashes the app here at reloadData in
- (void)viewWillAppear:(BOOL)animated {
[super viewWillAppear:animated];
[self.DXTableView reloadData];
}
You seem to have mixed up which view controller should be the delegate and which is the delegator. Also, you are just allocating a new instance of the AddDXTableViewController and assigning this as the delegate. This won't work; you need to have the existing instance of your view controller set as the delegate.
From what I can tell from your question, it is actually an instance of DXViewController that is to be the delegate of AddDXTableViewController
Presumably in DXViewController you have some code something like:
AddDXViewController *newViewController = [self.storyboard instantiateViewControllerWithIdentifier:#"AddDXViewController"];
[self.navigationController pushViewController:newViewController animated:YES];
What you need to do is set your delegate at this point:
AddDXViewController *newViewController = [self.storyboard instantiateViewControllerWithIdentifier:#"AddDXViewController"];
newViewController.delegate = self;
[self.navigationController pushViewController:newViewController animated:YES];
Having said all of that, since you are using a storyboard, a delegate is probably an unnecessarily complicated way of achieving your requirement; You can use a segue to move between the first and second view controller and an unwind segue to return back to the first. You can then implement prepareForSegue in the second view controller and use that to provide the array back to the first view controller
You have to make the UIViewController added in storyboard to AddDXTableViewController type in the identity inspector tab in story board.
See here the image
Here you can see the class type is ViewController, click on the dropdown and select the type to AddDXTableViewController
then type cast the viewController to AddDXTableViewController. As per my guess the instantiateViewControllerWithIdentifier: returns UIViewController which does not have delegate may cause the crash
AddDXTableViewController *addDXTVC = (AddDXTableViewController *)[self.storyboard instantiateViewControllerWithIdentifier:#"DXViewController"];
addDXTVC.delegate = self;
Let me know If it works

How to show viewcontroller from the view?

I searched for answers like Get to UIViewController from UIView? and couple of other answers but was not successful.
My issue is that I have a button in UIView lets say class1 and when I click on that button I want to load another view class2 which is UIViewController, and as I don't get navigationController in class1 I am unable to load the class2 view.
Please help me with this.
Thanks,
In Advance.
In general UIViews should not contain any logic that triggers the flow of app. This is the job of UIViewControllers. It's just a way of making the design of your code better and more organized.
One way I often use is to use a delegate pattern in my custom UIViews. Here is s simple setup:
In your MyCustomView .h file:
#class MyCustomView;
#protocol MyCustomViewDelegate <NSObject>
#optional
- (void)myViewDidTapOnButton:(MyCustomView)myCustomView;
#end
#interface MyCustomView : UIView
#property (weak, nonatomic) id <MyCustomViewDelegate> delegate;
#end
In your MyCustomView .m file:
- (IBAction)didTapMyButton:(id)sender {
if ([self.delegate respondsToSelector:#selector(myViewDidTapOnButton:)]) {
[self.delegate myViewDidTapOnButton:self];
}
}
Then in your viewcontroller, which is presenting your view:
interface:
#interface MyViewController ()<MyCustomViewDelegate>
#property (weak, nonatomic) IBOutlet UIView *myCustomView;
and implementation:
- (void)viewDidLoad {
[super viewDidLoad];
self.myCustomView.delegate = self;
}
- (void)myViewDidTapOnButton:(MyCustomView)myCustomView {
... code for presenting viewcontroller ...
}
Note:
Even if you dont use the parameter myCustomView which is sent in this method, its a common pattern and good habit to always send the sender of the delegate as the first parameter.
This is also used a lot by Apple, e.g. in
- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath;
Two cases :
If you are using storyboard then give your NavigationController a
storyboard id. And create an object of navigationController in your
custom UIView class.
If you have customized the app launching from AppDelegate create a
public property of your navigationController. From your UIView class create an object of appDelegate with [UIApplication sharedApplication].delegate. From this object access the navigationController property
When you have the navigationController object you can push your viewcontroller with:
[navigationController pushViewController:ViewController animated:YES];
First fill storyboard ID with "MyViewController", which is a String field that you can use to create a new ViewController based on that storyboard ViewController. And later access that view controller like this:
- (IBAction)buttonPressed:(id)sender{
MyCustomViewController *newvc = [self.storyboard instantiateViewControllerWithIdentifier:#"MyViewController"];
[self presentViewController:newvc animated:YES completion:nil];
}
When you click your button,you can do this:
YouViewController *yourViewController = [YouViewController new];
[self.view addSubView:yourViewController.view];
Hope to help you.

Calling method from viewcontroller to class xcode

I don't know if it is possible, but I would like to call a view controller's method in a class object. I have method like this in my view controller's .m file:
-(void)showLeaderBoard
{
GKLeaderboardViewController *leaderboardController = [[GKLeaderboardViewController alloc] init];
if (leaderboardController != nil){
leaderboardController.leaderboardDelegate = self;
[self presentModalViewController: leaderboardController animated: YES];
}
}
I would like to call that method in a SKScene file.
One way to do this is called delegation. In a nutshell, you allow the view controller to be the delegate on the object, so when the object wants to do something the view controller does, it can tell its delegate (the view controller) when to do it.
Step 1: Create the delegate property on the object (in the objects .h file):
// be sure to import the view controller's header here
#property (nonatomic, retain) YourViewControllerClass *delegate;
Step 2: When you create the object in your view controller, set the view controller as the objects delegate:
SKScene *theScene = // however you create your scene object here
theScene.delegate = self;
Step 3: Expose whatever method you want the object to call in the view controller's header:
- (void)showLeaderBoard;
Step 4: When you want to, tell the object's delegate to do whatever you want it to (inside the SKScene .m file):
[self.delegate showLeaderBoard];

Understanding the mechanism when passing data back from a second view controller to main view controller

I'm currently trying to have a better understanding on how the mechanisms of passing data between controllers work and I'm a little confused especially when passing data back from a second view controller to the main view controller.
This is what I have that works but don't fully understand. I have two view controllers, in the first one I have a button that when clicked it basically goes to the second view controller and a label which shows a message sent from the second view controller. In the second view controller I have a button and a textField, the button basically sends whatever is in the textfield to the label in main view controller.
Here is the code...
// FirstVC.h
#import <UIKit/UIKit.h>
#import "SecondVC.h"
#interface FirstVC : UIViewController <passNames>
#property (nonatomic, strong) NSString* firstNameString;
#property (weak, nonatomic) IBOutlet UILabel *firstNameLabel;
#end
//FirstVC.m
#import "FirstVC.h"
#implementation FirstVC
-(void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender
{
if ([[segue identifier]isEqualToString:#"secondController"])
{
UINavigationController *navController = segue.destinationViewController;
SecondVC *vc2 = (SecondVC*)navController.topViewController;
[vc2 setDelegate:self];
}
}
-(void)viewWillAppear:(BOOL)animated
{
self.firstNameLabel.text = _firstNameString;
}
-(void)setFirstName:(NSString *)firstName
{
_firstNameString = firstName;
}
#end
//SecondVC.h
#import <UIKit/UIKit.h>
#protocol passNames <NSObject>
-(void)setFirstName:(NSString*)firstName;
#end
#interface SecondVC : UIViewController
#property (retain)id <passNames> delegate;
- (IBAction)send:(UIBarButtonItem *)sender;
#property (nonatomic, strong) NSString *firstNameString;
#property (weak, nonatomic) IBOutlet UITextField *firstNameText;
#end
//SecondVC.m
#import "SecondVC.h"
#import "FirstVC.h"
#interface SecondVC ()
#end
#implementation SecondVC
- (IBAction)send:(UIBarButtonItem *)sender
{
_firstNameString = _firstNameText.text;
[[self delegate]setFirstName:_firstNameString];
[self dismissViewControllerAnimated:YES completion:nil];
}
#end
Can someone explain how the prepareForSegue method works in the above code? The reason for this question is because I added an NSLog and it looks like this method is only called in the transition from main view controller to the second controller. Why is this method needed if it is not called when transitioning from second view controller to main view controller which in my case is what I'm doing? It makes sense to use it when passing data from main view controller to a second controller not on the case shown above.
Can some explain the whole mechanism when passing data back to the main view controller?
FYI, I do understand about protocols and delegation.
Thanks a lot.
In your case, you are setting your delegate method of the second view controller to self in mainViewController in you prepareForSegue. This means that apart from navigating to the SecondViewController, you are implementing the callback mechanism in your main view controller, so that your delegate method gets called when the value is passed from the second view controller and this delegate method collects the value as a parameter to handle it in the main View Controller. You might have set the delegate of VC2 as self inn your prepareForSegue because you are creating the instance of VC2 in this method to navigate to the second controller.
Your goal is to hand back the data, like this:
[[self delegate] setFirstName:_firstNameString];
But you can't do that unless you know who to send setFirstName: to, and the compiler won't let you do it unless you guarantee that whoever you are sending setFirstName: to can accept that message.
That is what prepareForSegue prepares. FirstVC has declared that it adopts the passNames protocol, which means that it implements setFirstName:. And now you are saying:
[vc2 setDelegate:self];
...where self is the FirstVC instance. This solves both problems at once. The SecondVC instance (vc2) now has a delegate (the FirstVC instance), it is the right object to send the info back to, and because its delegate is declared as adopting passNames, we know that SecondVC can actually send setFirstName: to that delegate.
Now to the heart of your actual question: The reason for doing this in prepareForSegue is merely that this is the only moment when the FirstVC instance and the SecondVC instance "meet" one another! There is no other moment when the FirstVC instance has a reference to the SecondVC instance so as to be able to call setDelegate on it in the first place. If you weren't using segues and storyboards, the FirstVC would simply create the SecondVC instance directly - and would set itself as its delegate, just as you do:
SecondVC *vc2 = [SecondVC new];
UINavigationController *nav = [
[UINavigationController alloc] initWithRootViewController: vc2];
[vc2 setDelegate:self];
[self presentViewController: nav animated: YES completion: nil];
This is one reason I don't like storyboards: they muddy the story. It's all so simple and obvious when you don't use them and just do everything directly like this.

iPhone simple question: How to call a method from the main-class?

I have following code:
LoginViewController *lvc = [[LoginViewController alloc] initWithNibName:#"LoginViewController" bundle:nil];
[self presentModalViewController:lvc animated:false];
[lvc release];
That is called from my MainViewController.
Now, when the LoginViewController will be dismissed (of course this only happens when the login is correct) I must call a method in my MainViewController to load the initial data for my app.
I read a lot about delegate and tried it, but don't get it to work.
Could someone help me please?
(if possible, please with a few lines of code)
Any help is welcome!
I read a lot about delegate and tried it, but don't get it to work.
What have you tried really? Your LoginViewController must define a simple delegate protocol, and your MainViewController must conform to it.
All you need to do is add something like this in LoginViewController.h above #interface:
#protocol LoginViewControllerDelegate
- (void)loginViewControllerDidFinish;
#end
Which declares a protocol with one method. Then add this between #interface and #end:
#property (nonatomic, assign) id <LoginViewControllerDelegate> delegate;
Which means your login view controller will have a property called delegate which will point to an instance of any class (that's what id means) that conforms to it's delegate protocol (the thing between < and >). Don't forget to #synthesize delegate; inside .m file.
Now what you need to do is inside MainViewController.h add to #interface line like this:
#interface MainViewController : UIViewController <LoginViewControllerDelegate>
Which tells the compiler your MainViewController class conforms to this LoginViewControllerDelegate delegate protocol. Now implement the - (void)loginViewControllerDidFinish; method inside MainViewController.m and before presenting the login view controller modally set it's delegate to self (login.delegate = self;). When you are done inside your login view controller, before you dismiss it, call the delegate method on your delegate:
[self.delegate loginViewControllerDidFinish];
And that's it. Any more questions?
Try this:
1) when pushing login view, set some flag in MainViewController
2) in method viewWillAppear in MainViewController check that flag from 1). If it is set then load the initial data and unset flag. Otherwise push LoginView.
You've got an UIApplicationDelegate, and it should have an instance variable that points to the MainViewController. Expose this instance variable via a property, say mainViewController (on your UIApplicationDelegate), and then you can access it like this:
[(MyUIApplicationDelegate *)[[UIApplication sharedApplication] delegate] mainViewController]

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