Question

Ok, so am kind of new to programming for iPhones and Objective C and Cocoa Touch, but cannot figure this out. There is a lot of information when the delegate is self, but I am trying to send it to another file.

Here is some code…
I have the following method (I would normally call it a function but I think method is the correct terminology) in appDelegate.m

[GameUtil showAlertViewWithTag:1 delegate:self withTitle:@"" message:msg cancelButtonTitle:@"New game" otherButtonTitles:@"Main Menu", nil];

In GameUtil.h and .m I have showAlertViewWithTag set up properly and it is working fine.

The problem I am having, is with the delegate:self part … as it stands, when a button on alertview is clicked, it will go to -(void)alertView:(UIAlertView *)alertView clickedButtonAtIndex:(NSInteger)buttonIndex that is located in my appDelegate.m(which of course is expected when using self as the delegate).

But what I want it to do when a button is clicked is send it to -(void)alertView:.. in a different file called playField.m.

I have the alertview setup correctly in playField.m (have tested by calling alertview with delegate:self from within playField.m).

Basically I am stumped on how to tell the alertview in appDelegate.m to use a delegate that is in playField.m instead of delegate:self.

I think I need to #import playField.m or .h at into appDelegate.m but beyond that I am lost with all the @protocol @interface stuff.

Baby steps would be very helpful, like “You need to put XYZ at the top of your playField.h and ABC at the top of playField.m”.

I am hoping this is fairly simple to implement, and that I am just missing a few simple things.

Thanks in advance 🙂

Answer 1

First, even though the outcome of this is going to be that the delegate method will be in another file, you should rather think of it as “the delegate is another object”.
In your case, the delegate object is self, that is the App Delegate object. (because you’re writing this inside the app delegate implementation)

In order for the delegate to be another object, you first need to have an instance of that object accessible in your app delegate.

I am assuming your playField files hold a playField class. (I would have called it PlayField btw, classes are usually capitalized, and the objects (an instance of a class) are not, although it works either way.

Somewhere, you need to instantiate a playField object, have you done that somewhere? This would look like:

playField *pf=[[playField alloc] init];

If you haven’t done so, then do it above the showAlertViewCode.
In order for the classes to be available in your appDelegate, add:

#import "playField.h"

on top of your appDelegate file.

then in your alertview code, replace self by the object you just created:

[GameUtil showAlertViewWithTag:1 delegate:pf withTitle:@"" message:msg cancelButtonTitle:@"New game" otherButtonTitles:@"Main Menu", nil];

Now your delegate is the pf Object, which is an instance of playField, therefore the delegate method will be called from your playField.m implementation file.

Hope this makes sense!