Question

I would like to create a subclass of UIActionSheet that uses blocks instead of delegation. So I created the following class:

#import <UIKit/UIKit.h>

// Public Interface
typedef void (^FJActionSheetCompletion)(int buttonIndex);

@interface FJActionSheet : UIActionSheet

- (id)initWithTitle:(NSString *)title 
    completionBlock:(FJActionSheetCompletion)completionBlock
  cancelButtonTitle:(NSString *)cancelButtonTitle 
destructiveButtonTitle:(NSString *)destructiveButtonTitle 
  otherButtonTitles:(NSString *)otherButtonTitles, ... NS_REQUIRES_NIL_TERMINATION;

@end

// Private Interface
@interface FJActionSheet() <UIActionSheetDelegate>
{
    FJActionSheetCompletion _completionBlock;
}
@end

// Implementation
@implementation FJActionSheet

- (id)initWithTitle:(NSString *)title 
    completionBlock:(FJActionSheetCompletion)completionBlock
  cancelButtonTitle:(NSString *)cancelButtonTitle 
destructiveButtonTitle:(NSString *)destructiveButtonTitle 
  otherButtonTitles:(NSString *)otherButtonTitles, ...
{
    self = [super initWithTitle:title
                       delegate:self
              cancelButtonTitle:cancelButtonTitle
         destructiveButtonTitle:destructiveButtonTitle
              otherButtonTitles:otherButtonTitles];

    if (self)
    {
        _completionBlock = [completionBlock copy];
    }

    return self;
}

- (void)actionSheet:(UIActionSheet *)actionSheet didDismissWithButtonIndex:(NSInteger)buttonIndex
{
    _completionBlock(buttonIndex);
}

@end

This works except for one problem: I can not pass multiple strings for otherButtonTitles. If I do it as above, I (obviously) get a “Missing sentinel in method dispatch”.

My question is: How can I pass the otherButtonTitles argument to the initializer of UIActionSheet?

Answer 1

see this great blog post about variadic methods. Mainly how to access the variable arguments by using

va_list args;
va_start(args, firstArg);
va_arg(args, NSString*)