Question

I have this object of NSObject class. This object is shown on a view managed by a viewController. How do I get a reference to that viewController from inside the object’s class?

Answer 1

There is no “myViewController” property as you know. The easiest way to give any object access to some other object is through a delegate relationship.

Define a protocol for the delegate – typically in the module that wants access to the object which will be the delegate, i.e. the view controller

@protocol MyViewControllerDelegate

- (void)someActionTheViewControllerWillDo;

#end

Advertise the delegate support in the class implementing it

@interface MyViewController : UIViewController <MyViewControllerDelegate>
...
@end

Implement the function you defined as being part of the protocol in the view controller:

@implementation MyViewController

etc. etc.

#pragma mark -
#pragma mark MyViewControllerDelegateMethods

- (void)someActionTheViewControllerWillDo
{
  NSLog(@"I'm being called from an object that has me as a delegate");
}

etc. etc.

@end

Make a variable in the calling object to store the delegate object

@interface MyObject : NSObject
{

etc. etc.

  id<MyViewControllerDelegate> myDelegate;

etc. etc. 
}

Initialize that object

MyObject* myObject = [[MyObject alloc] initWithblahblah...
myObject.myDelegate = self
/* assuming myObject is being created in the view controller... */

In myObject – use the defined protocol to access methods in the delegate object!

[myDelegate someActionTheViewControllerWillDo];