Invoke methods declared in protocol from the class implementation - iphone

I've created a protocol named RecDelegate that's consisted of a method "- (void) doSmtng".
The protocol is defined in rec.h just before the rec interface declaration.
When I create a new application and adopt the RecDelegate to the new appDelegate, I can implement my own doSmtng, as needed to be.
What I don't understand is how can I invoke the doSmtng method from the rec.m (implementation of the class in which the protocol is defined...) - Meaning, how can I "Fire" the doSmtng in such a way that the new appDelegate's implementation will be triggered.
Hope what I said is relatively clear ... ;)
Thanks,
Guy.

There are two controllers below showing how to trigger an event from one to the other.
Wherever there is a comment "//HERE", it indicates there is delegation-related code.
SENDER OF DELEGATE
SecondViewController.h
#import <UIKit/UIKit.h>
#protocol SecondDelegate <NSObject> // HERE
#optional
-(void)MessageReceived:(NSString *)msg;
#end
#interface SecondViewController : UIViewController {
id<SecondDelegate> secondDelegate; // HERE
}
#property (assign) id<SecondDelegate> secondDelegate; // HERE
-(IBAction)trigger:(id)sender;
#end
SecondViewController.m
#import "SecondViewController.h"
#implementation SecondViewController
#synthesize secondDelegate; // HERE
-(IBAction)trigger:(id)sender {
if (self.secondDelegate != NULL && [self.secondDelegate respondsToSelector:#selector(MessageReceived:)]) { // HERE
[secondDelegate MessageReceived:#"my message"];
}
}
RECEIVER OF DELEGATE
FirstViewController.h
#import <UIKit/UIKit.h>
#import "SecondViewController.h" // HERE
#interface FirstViewController : UINavigationController <SecondDelegate> // HERE
-(void)MessageReceived:(NSString*)msg; // HERE
#end
FirstViewController.m
#import "FirstViewController.h"
#import "SecondViewController.h"
#implementation FirstViewController
// The designated initializer. Override if you create the controller programmatically and want to perform customization that is not appropriate for viewDidLoad.
- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil {
if ((self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil])) {
// Custom initialization
[self.view setBackgroundColor:[UIColor greenColor]];
SecondViewController *second = [[SecondViewController alloc] init];
[self pushViewController:second animated:YES];
second.secondDelegate = self; // HERE
[second release];
}
return self;
}
-(void)MessageReceived:(NSString *)msg { // HERE
int y = 0; // HERE IT IS !
}

You need to tell your Rec object that it should treat your AppDelegate as its delegate:
[rec setDelegate:appDelegate];
This could be done via Interface Builder or just after the Rec object is created.
Then, when the Rec object sends the delegate message to its delegate, the receiver will be your AppDelegate instance:
[[self delegate] doSmtng];
If the message the Rec object is sending to its delegate were an optional protocol message, it would instead be sent like this:
if ([[self delegate] respondsToSelector:#selector(optionalProtocolMethod)]) {
[[self delegate] optionalProtocolMethod];
}
The delegate will usually be declared something like:
#property(assign, nonatomic) id<RecDelegate> delegate;
Because it is not retained, in -dealloc, the Rec object only needs to nil it out, not release it:
delegate = nil;

Another way to do something like that is using NSNotificationCenter
in your RecDelegate init method add:
[[NSNotificationCenter defaultCenter] addObserver:self selector:#selector(doSmtng) name:#"someNotification" object:nil];
and in any another place / any class call
[[NSNotificationCenter defaultCenter] postNotificationName:#"someNotification" object:nil];

Related

Objective-c multiple delegates in the same view - ECSlidingViewController

I started testing ECSlidingViewController and after I tried to access FirstTopViewController I have a big trouble - because in FirstToViewController I already have ZBarReaderDelegate implemented and all examples of delegate are not triggering any method from my delegate.
Basically I have this stuff:
FirstTopViewController.h
#import ...MyStuff...
#import "UnderRightViewController.h"
#interface FirstTopViewController : UIViewController <RightViewDelegate, ZBarReaderDelegate>
#property (weak, nonatomic) IBOutlet UITextView *labelTotal;
#end
FirstTopViewController.m
#import "FirstTopViewController.h"
#implementation FirstTopViewController
- (void)setTotalViewController:(UnderRightViewController*)controller didTotalChange:(NSString*)total
{
//labelTotal.text = total;
NSLog(#"I'm here!!! and received %#", total);
}
From other side I have
UnderRightViewController.h
#import <UIKit/UIKit.h>
#import "ECSlidingViewController.h"
#class UnderRightViewController;
#protocol RightViewDelegate <NSObject>
- (void)setTotalViewController:(UnderRightViewController*)controller didTotalChange:(NSString*)total;
#end
#interface UnderRightViewController : UITableViewController
#property (nonatomic, weak) id <RightViewDelegate> delegate;
#end
UnderRightViewController.m
#import "UnderRightViewController.h"
#interface UnderRightViewController ()
#end
#implementation UnderRightViewController
#synthesize delegate;
- (void)viewDidAppear:(BOOL)animated
{
[super viewDidAppear:animated];
[delegate setTotalViewController:self didTotalChange:#"foo"];
}
#end
I'm trying this entire day solve this puzzle but I never get setTotalViewController fired.
Thanks in advance.
Friend you did a small mistake, when you navigate from FirstTopViewController to UnderRightViewController at that time you need to do this in FirstTopViewController.m:-
UnderRightViewController *obj = [[UnderRightViewController
alloc] initWithNibName:#"UnderRightViewController" bundle:nil];
obj.delegate = self; // u forget to assign protocol handler
[self.navigationController pushViewController:obj animated:YES];
[obj release];
You don't have any code that is setting the delegate for the UnderRightViewController. I don't know what object owns both of these controllers, but before either UnderRightViewController and FirstTopViewController are displayed it should run code something like this:
FirstTopViewController *ftvc = //... where ever you get a reference to this from
UnderRightViewController *urvc = ...;
urvc.delegate = ftvc;
In your above code you are using custom delegates and also you have used it for sending message to onecontroller class to another controller class. So below is the same sample code of custom delegates, it is working fine in similar way you have to implement and also the problem in your code is you are not setting the delegate, so please follow below how to set the same and call the method. here i have used your same method only return type i have defined as NSString in-spite of void for explaining purpose, but you can use void according to your requirement hope it will be helpful to you:-
First Controller Class AWindowController.h
#interface AWindowController : NSWindowController<sampleDelegate>
{
NSString *textA;
}
#property(readwrite,retain)NSString *textA;
-(IBAction)doSet:(id)sender;
#end
#import "AWindowController.h"
#import "BWindowController.h"
#interface AWindowController ()
#end
#implementation AWindowController
#synthesize textA;
- (id)initWithWindow:(NSWindow *)window
{
self = [super initWithWindow:window];
if (self) {
// Initialization code here.
}
return self;
}
- (NSString *)setTotalViewController:(BWindowController*)controller didTotalChange:(NSString*)total
{
NSLog(#"recieved");
return #"recieved";
}
- (void)windowDidLoad
{
[super windowDidLoad];
// Implement this method to handle any initialization after your window controller's window has been loaded from its nib file.
}
-(NSString*)windowNibName
{
return #"AWindowController";
}
-(IBAction)doSet:(id)sender
{
[self setTextA:#"Awindow Button Pressed"];
BWindowController *b=[[BWindowController alloc]init];
b.delegate=self;
[b showWindow:self];
}
#end
Second Controller Class BWindowController.h
#import <Cocoa/Cocoa.h>
#import "sampleDelegate.h"
#class BWindowController;
#protocol sampleDelegate <NSObject>
#required
//-(NSString *)getDataValue;
- (NSString *)setTotalViewController:(BWindowController*)controller didTotalChange:(NSString*)total;
#end
#interface BWindowController : NSWindowController<sampleDelegate>
{
NSString *bTextValue;
id<sampleDelegate>delegate;
}
#property(readwrite,retain)NSString *bTextValue;
#property(readwrite,assign)id<sampleDelegate>delegate;
#end
#import "BWindowController.h"
#interface BWindowController ()
#end
#implementation BWindowController
#synthesize bTextValue,delegate;
- (id)initWithWindow:(NSWindow *)window
{
self = [super initWithWindow:window];
if (self) {
// Initialization code here.
}
return self;
}
- (NSString *)setTotalViewController:(BWindowController*)controller didTotalChange:(NSString*)total;
{
return nil;
}
- (void)windowDidLoad
{
NSString *str= [[self delegate]setTotalViewController:self didTotalChange:#"recieved"];
self.bTextValue=str;
[super windowDidLoad];
// Implement this method to handle any initialization after your window controller's window has been loaded from its nib file.
}
-(NSString*)windowNibName
{
return #"BWindowController";
}
#end
Attached screen shot in Output:-
Below is window is the AwindowController.h class
Below in the same above window pressing the button and when Awindow button pressed data will send
and notification will be recieved in Bwindow using above define custom delegates as attached in the screen shot.

Delegates in iOS

I am a newbie to iOS world, so please ignore the obvious.
I am pushing a viewController(HelpViewController) on top of another viewController(MainViewController). When a particular action happens in the HelpViewController, I would like to update a variable inside the MainViewController. I understand for this I need to use delegate.
Here is my delegate header...
#protocol ViewControllerDelegate <NSObject>
#required
- (void) switchToggled:(BOOL)status;
#end
// Protocol Definition ends here
#interface ViewDelegate : NSObject
{
// Delegate to respond back
id <ViewControllerDelegate> _delegate;
}
#property (nonatomic,strong) id delegate;
-(void)sendMessage:(BOOL)status; // Instance method
#end
and implementation...
#implementation ViewDelegate
#synthesize delegate;
-(id)init {
self = [super init];
return self;
}
-(void)sendMessage:(BOOL)status
{
[delegate switchToggled:status];
}
- (void)dealloc
{
[super dealloc];
}
#end
So Now If I want to implement Protocol ViewControllerDelegate I need to specify in MainViewController, which I do as follows --
MainViewController <ViewControllerDelegate>
and
#pragma mark - ViewControllerDelegate delegate
-(void)switchToggled:(BOOL)status{
NSLog(#"Switch Toggled(%d) Message passed to MainViewController",status);
}
My question is how do I specify Object, which delegate property needs to point to, so that it can come back to MainViewController's "switchToggled".
One way I do is by having property inside HelpViewController as follows -
MainViewController.m
HelpViewController *helpVC = [[HelpViewController alloc] init];
helpVC.mainView = self;
[self.navigationController pushViewController:helpVC animated:YES];
[helpVC release];
HelpViewController.h
#property (nonatomic) MainViewController *mainView;
HelpViewController.m
#synthesize mainView;
ViewDelegate *myDelegate = [[ViewDelegate alloc] init];
// assign delegate
myDelegate.delegate = mainView;
[myDelegate sendMessage];
[myDelegate release];
Is this correct way to implement or there is better way to achieve this or am I totally wrong.
Thanks
You should do:
// HelpViewController.h
#protocol HelpDelegate
- (void)switchToggled:(BOOL)status;
#end
// HelpViewController.m
#interface HelpViewController : UIViewController
#property (nonatomic, assign) id<HelpDelegate> delegate;
- (id)initWithDelegate:(id<HelpDelegate>)delegate
#end
#implementation HelpViewController
- (id)initWithDelegate:(id<HelpDelegate>)delegate
{
if (self = [super init])
{
self.delegate = delegate;
}
}
- (void)sendMessage:(BOOL)status
{
[self.delegate switchToggled:status];
}
// MainViewController.h
#import "HelpViewController.h"
#interface MainViewController.h : UIViewController <HelpDelegate>
// MainViewController.m
- (void)someMethod
{
HelpViewController* viewController;
viewController = [HelpViewController alloc] initWithDelegate:self];
...
}
#pragma mark - Help Delegate
- (void)switchToggled:(BOOL)status
{
...
}
Give the delegate a name that makes clear to which class it belongs.
You don't need the extra class/files for ViewDelegate/ViewControllerDelegate. Just define the delegate in header of class it belongs to: HelpViewController.n in this case.
Similar: Implement the delegate method switchToggled: in the real class MainViewController, and not in the extra/unnecessary class ViewDelegate.
The purpose of delegates is to avoid class dependencies. By including MainViewController in HelpViewController you create such a dependency. This is not necessary as I show, and is wrong design.
You were also creating a circular dependency, because MainViewController already needed HelpViewController in order to show it, and now they need each other the other way around for sending the event.
Alternatively you can make HelpViewController's delegate public, have an init without argument, and expect users to set it with helpViewController.delegate = self; or something. But this would only make sense when the delegate being set is optional (which don't seems the case here, so adding it to the init method is appropriate).
I tell you what I would have done:
1) the protocol definition is ok, but do NOT create the class ViewDelegate, so:
//ViewControllerDelegate.h
#protocol ViewControllerDelegate <NSObject>
#required
- (void) switchToggled:(BOOL)status;
#end
2) Your implementation of the delegate method in MainViewController is ok.
3) Now... the important point:
//interface
#interface HelpViewController : UIViewController //or whatever superclass..
{
id <ViewControllerDelegate> _delegate;
}
#property (nonatomic,strong) id<ViewControllerDelegate> delegate;
#end
//implementation
#implementation HelpViewController
- (void)someMethodWhichCallsTheDelegate
{
//do something
...
// call delegate
//if switchToggled: were optional then add the following
//if ([self.delegate respondToSelector:#selector(switchToggled:)]) {
[self.delegate switchToggled:status];
}
#end
4) Now you have to assign the delegate:
//MainViewController.m
HelpViewController *helpVC = [[HelpViewController alloc] init];
helpVC.delegate = self;
[self.navigationController pushViewController:helpVC animated:YES];
[helpVC release];
And that's it!
BTW: if this delegate is related only to HelpViewControllerthen add the protocol definition where you define the interface of the class, it is not necessary to create a separate header file. If instead the protocol is "global", then it can have some sense to declare it separately.

event delegation

I have two uiviewcontroller: MainViewController and SecondaryViewControlle. In MainViewController I do:
[self.view addSubView:SecondaryViewControlle.view];
The SecondaryViewController is a button by pressing the function to be performed by a MainViewController. How to do?
You'd start by defining a protocol in your SecondViewControlle.h file, something like:
#protocol SecondViewControlleDelegate
- (void) doSomething
#end
You would also need to add a "delegate" ivar to your SecondViewControlle .h file. It would be the delegate line:
#interface SecondViewControlle : UIViewController
...
...
...
#property (nonatomic, assign) id delegate; // all you need to do is add this line inside your interface declarations
...
...
...
#end
Then, when you create / instantiate your SecondaryViewControlle from your MainViewController, make certain to add the MainViewController as the delegate like so:
SecondaryViewControlle.delegate = self;
[self.view addSubView:SecondaryViewControlle.view];
Now the "delegate" of your SecondaryViewControlle view controller points back to your MainViewController.
And when the button is pressed, you can simply do something like:
- (IBAction) buttonIsPressed: (id) sender
{
[delegate doSomething];
}
Now, I need to give you some advice here.
1 ) DO NOT use the class names as object names. Instead of having an object named "SecondViewControlle", name it something different (and start it with a lower case, which is Objective-C convention), something like "moreDetailVC".
2) I've told you how to do this with a delegate pattern, but this may not be the most appropriate way to do whatever it is that you're trying to do. After all, the MainViewController object (which should be renamed mainVC to differentiate the object from the class) is not on screen or visible so maybe there's a better place to put the functionality?
Option A
It's quicker, and easier, but lacks the maintainability, since there is no contract stating that SecondaryViewController needs to bother calling anything, and self.parentViewController could be any UIViewController.
Option B
The delegate pattern; this is my preference, it's obvious what's happening, what's required, and there's a nice solid contract that states, if you want to initialise me, give me a delegate.
Option C
If SecondaryViewController has to notify multiple objects, it would be quick to use the NSNotificationCenter, but as with Option A, there's no contract, should you need to notify many objects, you would need to remember to listen for notifications on those objects - since this is not the question, I won't go into detail, it's just here for the information
Option A
Within MainViewController.m, do something like so:
SecondaryViewController *viewcontroller = [[SecondaryViewController alloc] initWithNibName:#"SecondaryView" bundle:nil];
[self addChildViewController:viewcontroller];
//set viewcontroller.view frame
[self.view addSubview:viewcontroller.view];
[viewcontroller didMoveToParentViewController:self];
Inside MainViewController.h
-(void) performButtonClickAction;
Inside MainViewController.m:
-(void) performButtonClickAction {
//Do something constructive
}
and then inside the SecondaryViewController.m:
-(IBAction) buttonPressed:(id) sender {
[self.parentViewController performButtonClickAction];
}
Option B
Inside SecondaryViewController.h
#protocol SecondaryViewControllerDelegate <NSObject>
-(void) eventAFromViewController:(UIViewController *) viewController;
-(void) eventBFromViewController:(UIViewController *) viewController;
#end
#interface SecondaryViewController : UIViewController {
id<SecondaryViewControllerDelegate> delegate;
}
#property (assign, nonatomic) id<SecondaryViewControllerDelegate> delegate;
- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil delegate:(id<SecondaryViewControllerDelegate>) theDelegate;
#end
Inside SecondaryViewController.m
#synthesize delegate = _delegate;
- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil delegate:(id<SecondaryViewControllerDelegate>) theDelegate
{
self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
if (self) {
self.delegate = theDelegate;
}
return self;
}
-(IBAction) buttonPressed:(id) sender {
if( self.delegate != nil ) {
[_delegate eventAFromViewController:self];
}
else {
//No delegate
}
}

Why is my delegate method not being called?

In this code I'm attempting to pass an array from one tab view to another using protocols. The method itself is a simple get method with one line returning an a mutableArray. Within it's own class it works, within this class it is not even called.
- (void)viewDidLoad
{
[super viewDidLoad];
myLocationEntityArray = [[NSMutableArray alloc] initWithArray:[[self delegate] getMyLocationEntityArray]];
}
The header file for the class receiving the data:
#import <UIKit/UIKit.h>
#import <MapKit/MapKit.h>
#import <CoreLocation/CoreLocation.h>
#protocol CoreDataDelegate;
#interface ListTableViewController : UITableViewController
{
NSManagedObjectContext *managedObjectContext;
NSMutableArray *myLocationEntityArray;
id <CoreDataDelegate> delegate;
}
- (NSMutableArray *)fetchCoreData;
#property(nonatomic, retain) NSManagedObjectContext *managedObjectContext;
#property(nonatomic, assign) id <CoreDataDelegate> delegate;
#property(nonatomic, retain) NSMutableArray *myLocationEntityArray;
#end
#protocol CoreDataDelegate
//- (NSMutableArray *) fetchCoreData;
- (NSMutableArray *) getMyLocationEntityArray;
#end
The top of the header file sending the data:
#interface MapViewController : UIViewController <CLLocationManagerDelegate, CoreDataDelegate>
First you should change your procotol like this :
#protocol CoreDataDelegate
//- (NSMutableArray *) fetchCoreData;
- (void) getMyLocationEntityArray:(NSMutableArray *)entityArray;
#end
You set your MapViewController to responds to your protocol CoreDateDelegate. So, I suppose you alloc your ListTableViewController inside the MapViewController. If that is the case, you need to do this :
// MapViewController.m
...
ListTableViewController *listVC = [[ListTableViewController alloc] init];
listVC.delegate = self;
// display your listVC
...
// Somewhere in your code of MapViewController.m
- (void) getMyLocationEntityArray:(NSMutableArray *)entityArray {
// do something with entityArray
}
EDIT
Following your comments, here is a simpler way to do what you want. NSNotification. It does not require protocol, and is easier to implement.
// In ListTableViewController.m
// In Init or viewDidLoad function
[[NSNotificationCenter defaultCenter] addObserver:self
selector:#selector(getEntity:)
name:#"GetEntity"
object:nil];
- (void)getEntity:(NSNotification *)notif {
NSArray *entityArray = (NSArray *)[notif object];
// do something with entityArray
}
// In dealloc or viewDidUnLoad function
[[NSNotificationCenter defaultCenter] removeObserver:self
name:#"GetEntity"
object:nil];
// In MapViewController.m
// theEntityArray to be defined
[[NSNotificationCenter defaultCenter] postNotificationName:#"GetEntity"
object:theEntityArray
userInfo:nil];
In few words, when you will post the GetEntity notification in MapViewController, it will call undirectly the -(void)getEntity: function of ListTableViewController

iPhone application accessing data values from different classes

I have 4 classes i.e views in my application. Class A, having variable a and b.
After clicking on button which is on view A of class A it leads to class B, which is table view controller. Then class B leads to class C. then class C leads to class D.
Now i want to access values of a and b of class A into class D. I tried it with NSNotification but not succeeded.
Please suggest.
I tried with NSNotification:
i tried with NSNotification like Class A---
-(IBAction) selectButton:(id) sender{
NSString * a = [NSString stringWithFormat:#"Manjinder singh"];
NSDictionary * dict = [NSDictionary dictionaryWithObject:a forKey:#"1"];
[[NSNotificationCenter defaultCenter] postNotificationName:#"sendMessage" object:self userInfo:dict];
}
Then Class D----
- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil
{
self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
if (self) {
[[NSNotificationCenter defaultCenter] addObserver:self selector:#selector(sendMessage:) name:#"sendMessage" object:nil];
}
return self;
}
-(void)sendMessage:(NSNotification *)notification{
A *dil=[[A alloc] init];
nslog(#"dil.a");
NSLog(#"USERINFO:MyUserInfo (its a dictionary):%#",[[notification userInfo] valueForKey:#"1"]);
}
This is the rendom try but basically i want to show variable a and b of class A into class D.
Update:------------
MyCoolViewController.h// a class where data send from
#protocol MyCoolViewDelegate;
#interface MyCoolViewController : UIViewController {
id <MyCoolViewDelegate> delegate;//
}
#property (nonatomic, assign) id delegate;//
#end
#protocol MyCoolViewDelegate <NSObject>//
-(void)sendAStringToAnotherView:(NSString*)string;
#end
MyCoolViewController.m
-(void)viewDidLoad{
[delegate sendAStringToAnotherView:#"this is a string"];
}
firstViewController.m //a class where data sent
-(void)viewDidLoad{
MyCoolViewController *myViewControllerPointer=[[MyCoolViewController alloc] init];
myViewControllerPointer.delegate = self;//
}
-(void)sendAStringToAnotherView:(NSString*)string
{
//displays the string as console output
NSLog(#"plzzzzzz show data",string);
}
value of string is not passed to this class because it is not showing in NSLog output.
UPDATED 2---
MyCoolViewController.m
#import “MyCoolViewController.h”
#import "firstViewController.h"
#implementation MyCoolViewController
#synthesize label1,sttr;
#synthesize delegate;//
-(IBAction) selectButton:(id) sender{
if (curri==nil) {
curri=[[CurrancyViewController alloc] initWithNibName:nil bundle:nil];
[self.navigationController pushViewController:curri animated:YES];
}
curri=nil;
//CHECK ThIS [curri release];
}
- (void)viewDidLoad
{
[delegate sendAStringToAnotherView:#"this is a string"];
self.view.backgroundColor = [UIColor colorWithPatternImage:[UIImage imageNamed:#"background1.png"]];
[super viewDidLoad];
}
- (BOOL)shouldAutorotateToInterfaceOrientation: (UIInterfaceOrientation)interfaceOrientation
{
// Return YES for supported orientations
return (interfaceOrientation == UIInterfaceOrientationPortrait);
}
#end
Can you give more context about what specifically you are trying to achieve? It sounds like you want to pass data between several UIViewControllers. Here is how to set up a delegate for one of your view controllers:
#import <UIKit/UIKit.h>
#protocol MyCoolViewControllerDelegate;
#interface MyCoolViewController : UIViewController {
id <MyCoolViewControllerDelegate> delegate;
}
#property (nonatomic, assign) id delegate;
#end
#protocol MyCoolViewControllerDelegate <NSObject>
-(void)sendAStringToAnotherView:(NSString*)string;
#end
Then you will should synthesize the delegate
#synthesize delegate;
and then when you want to pass data to, lets say a parent view, call this function:
[delegate sendAStringToAnotherView:#"this is a string"];
In the other view controller, wherever you instantiated the instance of this UIViewController, you need to set that self as the delegate;
myViewControllerPointer.delegate = self;
and then implement the delegate function in the parent view controller.
-(void)sendAStringToAnotherView:(NSString*)string
{
//displays the string as console output
NSLog(string);
}
The fact that you need communicate between views like this could possibly mean that there is a more efficient means of structuring your app. Can't say for sure without more info.
Try and use this template to add a delegate to your own app.
You could use delegation here
D would become the delegate of A, and when you click the button, A sends a message to D with the variables as arguments and D responds by performing a method.