Question

I am writing a category against NSMutableString that uses appendFormat: internally.

@interface NSMutableString (Additions)    
- (void)appendFormatWithLine:(NSString *)format, ...;    
@end

@implementation NSMutableString (Additions)

- (void)appendFormatWithLine:(NSString *)format, ... {
    va_list args;
    va_start(args, format);

    // **calling [self appendFormat] gives a 'EXC_BAD_ACCESS'**
    [self appendFormat:format, args];
    [self appendString:@"\r\n"];

    va_end(args);
}

@end

I have no idea how to use va_list or va_start to call NSMutableString:appendFormat. How can this be done?

Answer 1

Well yeah. -appendFormat: takes variadic arguments, not a variadic argument list (va_list.) There’s no single method on NSMutableString that takes an argument list, so you should do this instead:

NSString *formatted = [[NSString alloc] initWithFormat: format arguments: args];
if (formatted) {
    [self appendString: formatted];
    [formatted release];
}