how to pass data to the parent class in ios? - ios

Question

I am a beginner in objective-C. So please forgive if my question is silly.
In my root view controller A, I added a subview B.
In b there will be another subview C. C contains another subview D.
How can I call a method in A from D.
I know that we can use delegates for passing data to the parent controller.
But my question is that do i need to create delegate which calls C from D and another one for call B from C and so on?
Or is there any method which directly calls a method in A from D?

Answer 1

But my question is that do i need to create delegate which calls C from D and another one for call B from C and so on?
The view controller's job is to manage it's view and all of that view's subviews. If you've got a view that needs to send the view controller a message, like a control that needs to send a message somewhere when the user changes its value, then the view controller should be aware that it's there. In such a case, the view controller can take care of setting itself (or some other appropriate object) as said subview's delegate or target when the view hierarchy is loaded, like this:
- (void)viewDidLoad
{
self.needControl.delegate = self;
}
That way, the needy control doesn't need to know anything about the object that is its delegate. It's not assuming that the object is the view controller, or its parent view, or anything else. All it cares about is that it has a delegate, and that its delegate implements the necessary methods. And that, in turn, helps you keep your code more flexible and maintainable and maybe even reusable.

Answer 2

Do i need to create delegate which calls C from D and another one for call B from C and so on? No
You can use a single delegate to call a method in A from D. From your comments i came to know B,C,D are UIView's controlled your root view controller. So the job is easy you need to set a delegate as its root view controller upon creating each sub views.
1. View B is creating from the root view controller itself so viewB.delegate = self
2. View C is creating from the view B so viewC.delegate = self.delegate
3. Repeat same for view D also
Now all your views are controlled by your delegate rootViewController.
Finally This answer will help you to complete your task

Answer 3

You should structure your code so that class D does not know class A exists at all.
There are a few specific techniques that are common in iOS/Mac programming:
class D has a delegate property, and calls methods on it. Use this when only one object can receive the delegate method, particularly useful for things like a button asking if it should be enabled or disabled right now. Use interface builder to set the delegate of the view to your instance of class A.
class D should have a "target" property (type id) and an "action" property (type SEL), and it sends the action message/selector to the target object. useful for when a view has a specific single action that it triggers, such as when a button is pressed, or the user presses Enter in an text field. Use interface builder to set the target and action of the view to your instance of class A.
class D sends messages and metadata to [NSNotificationCenter defaultCenter], and class A tells the notification center that it wants to observe those notifications. Useful when potentially many objects need to be notified when something happened, such as when a text field receives or looses keyboard focus.
class D has a property or properties sends Key Value Observing notifications whenever it the value of the property changes. Class A would tell the Key Value Observing system that it wants to know whenever a specific property on class D changes. This is useful when you care specifically about some data, such as when the value of a text field changes.
All of these techniques are described in more detail here on stack overflow or in Apple's official documentation.
Class B and C also should not know that class A exists. Class A should be the one that knows how to find the other objects, unless you can use interface builder (the first two options allow that).

Answer 4

Add your A_viewCon.h file into your D_viewCon.h file
create object of A_viewCon and set #property and #synthesize as properly.
call method of A_viewCon in D_viewConwrite following code.
[self.objectOFA_viewCon performSelector:#selector(MethodNameOFA_viewCon) withObject:nil afterDelay:0];

Answer 5

U can register Class A to observe a NSNotification like ->
- (void)addObserver:(id)observer selector:(SEL)aSelector name:(NSString *)aName object:(id)anObject;
and post NSNotifications from Object of class D like ->
- (void)postNotificationName:(NSString *)aName object:(id)anObject userInfo:(NSDictionary *)aUserInfo;
This way u do not need to keep a reference/delegate and still u can communicate between alive objects.