I extend NSOperation (call it A) which contains NSOperationQueue for other NSOperations (which is another extended class different from A, call these operations B). When operation A is running (executing B operations) how do i call a specific function/method on operation A when certain event takes place on B operations? For example every operation B that finishes it calls a function on operation A returning itself?

*Nested NSOperation and NSOperationQueue(s)

Hope this mockup pseudo code can help to draw the picture.

//My classes extended from NSOperation

NSOperation ClassA

NSOperation ClassB

//MainApp

-(void)applicationDidFinishLaunching:(NSNotification *)aNotification {

    ClassA A1;

    ClassA A2;

    NSOperationQueue Queue;
    Queue AddOperation: A1;
    Queue AddOperation: A2;


}

//Main of ClassA

-(void)main {

     ClassB B1;

     ClassB B2;

     NSOperationQueue Queue;
     Queue AddOperation: B1;
     Queue AddOperation: B2;

}

//Main of ClassB

-(void)main {

   //Do some work and when done call selector on ClassA above

}