how to pass variable arguments to another method?

Question

i have googled and came to know that how to use the variable arguments. but i want to pass my variable arguments to another method. i m getting errors. how to do that ?

-(void) aMethod:(NSString *) a, ... {   [self anotherMethod:a];    // i m doing this but getting error. how to pass complete vararg to anotherMethod } 

Answer 1

AFAIK ObjectiveC (just like C and C++) do not provide you with a syntax that allows what you directly have in mind.

The usual workaround is to create two versions of a function. One that may be called directly using ... and another one called by others functions passing the parameters in form of a va_list.

 .. [obj aMethod:@"test this %d parameter", 1337); [obj anotherMethod:@"test that %d parameter", 666); ..  -(void) aMethod:(NSString *)a, ...  {     va_list ap;     va_start(ap, a);      [self anotherMethod:a withParameters:ap];       va_end(ap); }  -(void) anotherMethod:(NSString *)a, ... {     va_list ap;     va_start(ap, a);      [self anotherMethod:a withParameters:ap];       va_end(ap); }  -(void) anotherMethod:(NSString *)a withParameters:(va_list)valist  {     NSLog([[[NSString alloc] initWithFormat:a arguments:valist] autorelease]); } 

Answer 2

You cannot pass variadic arguments directly. But some of these methods provide an alternative that you can pass a va_list argument e.g.

#include <stdarg.h>  -(void)printFormat:(NSString*)format, ... {    // Won't work:    //   NSString* str = [NSString stringWithFormat:format];     va_list vl;    va_start(vl, format);    NSString* str = [[[NSString alloc] initWithFormat:format arguments:vl] autorelease];    va_end(vl);     printf("%s", [str UTF8String]); }