Question

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);   } }