What is this Objective-C syntax, ellipse style dot notation? "..."

Question

Hi all,

I noticed this in Joe Hewitt's source for Three20 and I've never seen this particular syntax in Objective-C before. Not even sure how to reference it in an appropriate Google search.

From TTTableViewDataSource:

+ (TTSectionedDataSource*)dataSourceWithObjects:(id)object,... {

The "..." is what's throwing me off here. I'm assuming it's a form of enumeration where a variable amount of arguments may be supplied. If it is, what's the official name for this operator and where can I reference the documentation for it?

Thank you kindly.

Answer 1

It's a variadic method, meaning it takes a variable number of arguments. This page has a good demonstration of how to use it:

#import <Cocoa/Cocoa.h>

@interface NSMutableArray (variadicMethodExample)

- (void) appendObjects:(id) firstObject, ...;  // This method takes a nil-terminated list of objects.

@end

@implementation NSMutableArray (variadicMethodExample)

- (void) appendObjects:(id) firstObject, ...
{
id eachObject;
va_list argumentList;
if (firstObject)                      // The first argument isn't part of the varargs list,
  {                                   // so we'll handle it separately.
  [self addObject: firstObject];
  va_start(argumentList, firstObject);          // Start scanning for arguments after firstObject.
  while (eachObject = va_arg(argumentList, id)) // As many times as we can get an argument of type "id"
    [self addObject: eachObject];               // that isn't nil, add it to self's contents.
  va_end(argumentList);
  }
}