How to call super in an init method with nil terminated list of params?

Question

I am subclasing UIAlertView. I would like to implement a init method with the following signature:

- (id)initWithTitle:(NSString *)title 
            message:(NSString *)message
         identifier:(NSInteger)ident
           delegate:(id)delegate 
  cancelButtonTitle:(NSString *)cancelButtonTitle 
  otherButtonTitles:(NSString *)otherButtonTitles,...

It is just the default UIAlertView method with an added param identifier.

- (id)initWithTitle:(NSString *)title 
            message:(NSString *)message
           delegate:(id)delegate 
  cancelButtonTitle:(NSString *)cancelButtonTitle 
  otherButtonTitles:(NSString *)otherButtonTitles,...

What is the correct syntax now to invoke the super method if I don't know in compile time what my init method otherButtonTitles params will be?

self = [super initWithTitle:title
                    message:message
                   delegate:delegate
          cancelButtonTitle:cancelButtonTitle 
          otherButtonTitles:otherButtonTitles, nil];
//I will only get the first param with this syntax

This isn't possible. See [Subclassing UIAlertView](http://stackoverflow.com/questions/8309869/subclassing-uialertview). — jscs, May 28 '12 at 18:37

Oleg Trakhman · Accepted Answer · 2012-05-28T10:54:28.857

First, Learn about variadic functions, it can help you: Wikipedia

Example:
#include <stdarg.h>

void logObjects(id firstObject, ...) // <-- there is always at least one arg, "nil", so this is valid, even for "empty" list
{
  va_list args;
  va_start(args, firstObject);
  id obj;
  for (obj = firstObject; obj != nil; obj = va_arg(args, id)) // we assume that all arguments are objects
    NSLog(@"%@", obj);
  va_end(args);
}

Second, it's better to make an Objectve-C Category rather than subclass UIAlertView

Example:
@interface UIAlertView(Identifiers)
- (id)initWithTitle:(NSString *)title 
            message:(NSString *)message
         identifier:(NSInteger)ident
           delegate:(id)delegate 
  cancelButtonTitle:(NSString *)cancelButtonTitle 
  otherButtonTitles:(NSString *)otherButtonTitles,...;
@end

score 0 · Answer 2 · answered May 28 '12 at 10:48

The docs say

Subclassing Notes
The UIAlertView class is intended to be used as-is and does not support subclassing. The view hierarchy for this class is private and must not be modified.

But to the point I don't think you can. You could always just recreate this convenience method by implementing a normal init and then configuring the object with the arguments passed in.

How to call super in an init method with nil terminated list of params?

2 Answers2