Question

I came around a interesting issue while working on my app. Imagine the scenerio where

• There exist one object, Lets call it A.
• A, then creates an object(B) of some delegation based class, say NSURLConnection.
• A assigned itself as delegate of B, provided A has implemented all the required delegate methods.
• A asks B to start its processing. In our example i.e. fetching data from some server.
• As soon as B finished fetching data, it will call some specified method of A.

In the last step, suppose while calling the methods of A, B finds that the A object doesnt exist anymore. Then what happens???

I’m not sure but does it cause crash?

If yes, then please suggest me how to avoid the situation.

In my case I assigned the viewcontroller as delegate of some object, say X in viewDidLoad method. There are cases when viewcontroller get destroyed before X calls the delegate methods defined in the viewcontroller.

• If assigning X’s delegate to nil solves the problem. Then where
  should i do that.

In short, which method is called only once while unloading phase of view controller likewise
viewDidLoad in its loading phase.

Answer 1

Checking against a valid delegate object should be sufficient enough.

if (delegate)
   [delegate method];