如何写format函数

FOUNDATION_EXPORT void NSLog(NSString *format, ...) NS_FORMAT_FUNCTION(1,2);
FOUNDATION_EXPORT void NSLogv(NSString *format, va_list args) NS_FORMAT_FUNCTION(1,0);

 

EG1:

VSLog(char* format, ...)

{

    char pbuffer[2048];

    va_list argptr;
    va_start(argptr, format);
    vsprintf(pbuffer, format, argptr);
    va_end(argptr);

}

 

 

EG2:
+ (void)file:(char*)sourceFile function:(char*)functionName lineNumber:(int)lineNumber format:(NSString*)format,...
{
    NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];
    @try {
        va_list ap;
        NSString *print, *file, *function;
        va_start(ap,format);
        if (sourceFile != NULL) {
            file = [[[NSString alloc] initWithBytes: sourceFile
                                            length: strlen(sourceFile)
                                          encoding: NSUTF8StringEncoding] autorelease];
            file = [file lastPathComponent];
        }else {
            file = @"";
        }
        if (functionName != NULL) {
            function = [NSString stringWithUTF8String: functionName];
        }else{
            function = @"";
        }
       
        print = [[NSString alloc] initWithFormat: format arguments: ap];
        if (print == nil) {
            print = @"";
        }
       
        va_end(ap);   
       
        NSLog(@"%@:%d %@; %@", file, lineNumber, function, print);   
        [print release];   
    }
    @catch (NSException * e) {
    }
    @finally {
       
    }
   
    [pool release];
}

/* * ISO C Standard: 7.15 Variable arguments <stdarg.h> */ #ifndef _STDARG_H #ifndef _ANSI_STDARG_H_ #ifndef __need___va_list #define _STDARG_H #define _ANSI_STDARG_H_ #endif /* not __need___va_list */ #undef __need___va_list /* Define __gnuc_va_list. */ #ifndef __GNUC_VA_LIST #define __GNUC_VA_LIST typedef __builtin_va_list __gnuc_va_list; #endif /* Define the standard macros for the user, if this invocation was from the user program. */ #ifdef _STDARG_H #define va_start(v,l) __builtin_va_start(v,l) #define va_end(v) __builtin_va_end(v) #define va_arg(v,l) __builtin_va_arg(v,l) #if !defined(__STRICT_ANSI__) || __STDC_VERSION__ + 0 >= 199900L #define va_copy(d,s) __builtin_va_copy(d,s) #endif #define __va_copy(d,s) __builtin_va_copy(d,s) /* Define va_list, if desired, from __gnuc_va_list. */ /* We deliberately do not define va_list when called from stdio.h, because ANSI C says that stdio.h is not supposed to define va_list. stdio.h needs to have access to that data type, but must not use that name. It should use the name __gnuc_va_list, which is safe because it is reserved for the implementation. */ #ifdef _HIDDEN_VA_LIST /* On OSF1, this means varargs.h is "half-loaded". */ #undef _VA_LIST #endif #ifdef _BSD_VA_LIST #undef _BSD_VA_LIST #endif #if defined(__svr4__) || (defined(_SCO_DS) && !defined(__VA_LIST)) /* SVR4.2 uses _VA_LIST for an internal alias for va_list, so we must avoid testing it and setting it here. SVR4 uses _VA_LIST as a flag in stdarg.h, but we should have no conflict with that. */ #ifndef _VA_LIST_ #define _VA_LIST_ #ifdef __i860__ #ifndef _VA_LIST #define _VA_LIST va_list #endif #endif /* __i860__ */ typedef __gnuc_va_list va_list; #ifdef _SCO_DS #define __VA_LIST #endif #endif /* _VA_LIST_ */ #else /* not __svr4__ || _SCO_DS */ /* The macro _VA_LIST_ is the same thing used by this file in Ultrix. But on BSD NET2 we must not test or define or undef it. (Note that the comments in NET 2's ansi.h are incorrect for _VA_LIST_--see stdio.h!) */ #if !defined (_VA_LIST_) || defined (__BSD_NET2__) || defined (____386BSD____) || defined (__bsdi__) || defined (__sequent__) || defined (__FreeBSD__) || defined(WINNT) /* The macro _VA_LIST_DEFINED is used in Windows NT 3.5 */ #ifndef _VA_LIST_DEFINED /* The macro _VA_LIST is used in SCO Unix 3.2. */ #ifndef _VA_LIST /* The macro _VA_LIST_T_H is used in the Bull dpx2 */ #ifndef _VA_LIST_T_H /* The macro __va_list__ is used by BeOS. */ #ifndef __va_list__ typedef __gnuc_va_list va_list; #endif /* not __va_list__ */ #endif /* not _VA_LIST_T_H */ #endif /* not _VA_LIST */ #endif /* not _VA_LIST_DEFINED */ #if !(defined (__BSD_NET2__) || defined (____386BSD____) || defined (__bsdi__) || defined (__sequent__) || defined (__FreeBSD__)) #define _VA_LIST_ #endif #ifndef _VA_LIST #define _VA_LIST #endif #ifndef _VA_LIST_DEFINED #define _VA_LIST_DEFINED #endif #ifndef _VA_LIST_T_H #define _VA_LIST_T_H #endif #ifndef __va_list__ #define __va_list__ #endif #endif /* not _VA_LIST_, except on certain systems */ #endif /* not __svr4__ */ #endif /* _STDARG_H */ #endif /* not _ANSI_STDARG_H_ */ #endif /* not _STDARG_H */