Setting delegate in "unrelated" class

Question

I am having trouble using a protocol to get some data from another class. I can't see how to set the delegate in a class that doesn't segue to the MVC that needs the data. I create the protocol in the MVC and implement the method(s) in some arbitrary class that contains the data I need. But I can't see how to refer back to the delegator MVC to set the delegate if there is no reference to the delegator MVC, like when you use segue.destinationViewController.

That's a bit hard to understand. Can you post some code, please? — emrys57, Nov 30 '12 at 17:12
I don't have any code to post that would help because I don't know how to do this so I'll try to explain it better. I have an MVC (MyViewController) that puts some data into a view. Sometimes I need additional data from some other class (SomeDataClass). I create a protocol with a method and a delegate in MyViewController. I implement the protocol method in SomeDataClass. Now, how do I set the delegate in MyViewController to point to SomeDataClass as the delegate? I don't have a reference to MyViewController, so can't reference the delegate to set it. — Bob, Nov 30 '12 at 17:27

score 1 · Answer 1 · answered Nov 30 '12 at 17:49

Something like this?

@implementation MyViewController {
// keep a pointer to the data supplier class as long as this object exists
// so that it will continue to exist and send me delegate callbacks
SomeDataClass *myInstanceOfSomeDataClass; // instance variable to point to my data supplier
}

// ...

- (void)updateMyView {
    if (myInstanceOfSomeDataClass == NULL) // I haven't created an instance yet
        myInstanceOfSomeDataClass = [[SomeDataClass alloc] init];
    SomeType *results;
    if (instantResultsAreAvailable)
        results = [myInstanceOfSomeDataClass getResults];
    if (resultsAreOnlyAvailableFromDelegateCallback)
        myInstanceOfSomeDataClass.delegate = self;
}

- (void) delegateCallbackMethod {
//...
}
@end

OK, so if there is no existing relationship between the 2 classes and I don't want to make an instance, there is no way to use delegation. — Bob, Nov 30 '12 at 22:34

score 1 · Accepted Answer · answered Nov 30 '12 at 17:52

1

If MyViewController can create the instance of SomeDataClass, then you set the delegate there. If there is no connection between the controllers, then you might use an NSNotification instead. That is a completely anonymous way to connect instances -- you send out a notification, and any class that registers for that notification can get it.

answered Nov 30 '12 at 17:52

rdelmar

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That is the solution I was considering, but wanted to take a shot at using delegation to do this if possible. Looks like it isn't for what I wanted to do. – Bob Nov 30 '12 at 22:35

score 0 · Answer 3 · edited May 23 '17 at 11:56

0

you want to pass data from one from viewcontroller to another class? just go through this Passing Data between View Controllers

edited May 23 '17 at 11:56

Community

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answered Nov 30 '12 at 17:21

kumar_android

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Setting delegate in "unrelated" class

3 Answers3