How to print out the method name and line number and conditionally disable NSLog

Question

I m doing a presentation on debugging in Xcode and would like to get more information on using NSLog efficiently   In particular  I have two questions    is there a way to easily NSLog the current method s name   line number  is there a way to  disable  all NSLogs easily before compiling for release code

User · Accepted Answer

Here are some useful macros around NSLog I use a lot:

#ifdef DEBUG
#   define DLog(fmt, ...) NSLog((@"%s [Line %d] " fmt), __PRETTY_FUNCTION__, __LINE__, ##__VA_ARGS__)
#else
#   define DLog(...)
#endif

// ALog always displays output regardless of the DEBUG setting
#define ALog(fmt, ...) NSLog((@"%s [Line %d] " fmt), __PRETTY_FUNCTION__, __LINE__, ##__VA_ARGS__)

The DLog macro is used to only output when the DEBUG variable is set (-DDEBUG in the projects's C flags for the debug confirguration).

ALog will always output text (like the regular NSLog).

The output (e.g. ALog(@"Hello world") ) will look like this:

-[LibraryController awakeFromNib] [Line 364] Hello world

User · Answer

NSLog    s  d  s  s     FILE      LINE      PRETTY FUNCTION      FUNCTION       Outputs file name  line number  and function name    proj cocoa cdcli cdcli m 121 managedObjectContext managedObjectContext     FUNCTION   in C   shows mangled name   PRETTY FUNCTION   shows nice function name  in cocoa they look the same   I m not sure what is the proper way of disabling NSLog  I did    define NSLog   And no logging output showed up  however I don t know if this has any side effects

User · Answer

building on top of above answers  here is what I plagiarized and came up with  Also added memory logging    import  lt mach mach h gt    ifdef DEBUG     define DebugLog fmt       NSLog     s  d    fmt     PRETTY FUNCTION      LINE        VA ARGS      else     define DebugLog       endif    define AlwaysLog fmt       NSLog     s  d    fmt     PRETTY FUNCTION      LINE        VA ARGS        ifdef DEBUG     define AlertLog fmt                UIAlertView  alert     UIAlertView alloc                initWithTitle    NSString stringWithFormat    s Line   d       PRETTY FUNCTION      LINE                       message    NSString stringWithFormat   fmt      VA ARGS                      delegate   nil          cancelButtonTitle     Ok           otherButtonTitles   nil         alert show       else     define AlertLog       endif     ifdef DEBUG     define DPFLog NSLog    s  d      PRETTY FUNCTION      LINE      Debug Pretty Function Log  else     define DPFLog  endif    ifdef DEBUG     define MemoryLog        struct task basic info info       mach msg type number t size   sizeof info        kern return t e   task info mach task self                                        TASK BASIC INFO                                       task info t  amp info                                       amp size        if KERN SUCCESS    e             NSNumberFormatter  formatter     NSNumberFormatter alloc  init              formatter setNumberStyle NSNumberFormatterDecimalStyle             DebugLog      bytes    formatter stringFromNumber  NSNumber numberWithInteger info resident size            else            DebugLog   Error with task info     s   mach error string e               else     define MemoryLog  endif

User · Answer

There are a new trick that no answer give  You can use printf instead NSLog  This will give you a clean log   With NSLog you get things like this    2011-11-03 13 43 55 632 myApp 3739 207  Hello Word   But with printf you get only   Hello World   Use this code   ifdef DEBUG      define NSLog FORMAT       fprintf stderr   s n     NSString stringWithFormat FORMAT      VA ARGS    UTF8String     else      define NSLog                        endif

User · Answer

It s easy to change your existing NSLogs to display line number and class from which they are called  Add one line of code to your prefix file    define NSLog   FORMAT         NSLog     s  Line  d      FORMAT       PRETTY FUNCTION      LINE        VA ARGS

User · Answer

Disabling all NSLogs  for somebody allergic to MACROS  here is something that you can compile too   void SJLog NSString  format            if LOG                   va list args          va start args format           NSLogv format  args           va end args             And  use it almost like NSLog   SJLog   bye bye NSLogs        From this blog  https   whackylabs com logging ios 2011 01 19 ios-moving-in-and-out-of-nslogs

User · Answer

To complement the answers above  it can be quite useful to use a replacement for NSLog in certain situations  especially when debugging  For example  getting rid of all the date and process name id information on each line can make output more readable and faster to boot   The following link provides quite a bit of useful ammo for making simple logging much nicer   http   cocoaheads byu edu wiki a-different-nslog

User · Answer

I ve taken DLog and ALog from above  and added ULog which raises a UIAlertView message   To summarize    DLog will output like NSLog only when the DEBUG variable is set  ALog will always output like NSLog ULog will show the UIAlertView only when the DEBUG variable is set      ifdef DEBUG     define DLog fmt       NSLog     s  Line  d    fmt     PRETTY FUNCTION      LINE        VA ARGS      else     define DLog       endif  define ALog fmt       NSLog     s  Line  d    fmt     PRETTY FUNCTION      LINE        VA ARGS      ifdef DEBUG     define ULog fmt          UIAlertView  alert     UIAlertView alloc  initWithTitle  NSString stringWithFormat    s n  Line  d       PRETTY FUNCTION      LINE    message  NSString stringWithFormat fmt      VA ARGS     delegate nil cancelButtonTitle   Ok  otherButtonTitles nil    alert show      else     define ULog       endif   This is what it looks like      1 Diederik

User · Answer

For some time I ve been using a site of macros adopted from several above  Mine focus on logging in the Console  with the emphasis on controlled  amp  filtered verbosity  if you don t mind a lot of log lines but want to easily switch batches of them on  amp  off  then you might find this useful    First  I optionally replace NSLog with printf as described by  Rodrigo above   define NSLOG DROPCHAFF  comment out to get usual date time  etc 2011-11-03 13 43 55 632 myApp 3739 207  Hello Word   ifdef NSLOG DROPCHAFF  define NSLog FORMAT       printf   s n     NSString stringWithFormat FORMAT      VA ARGS    UTF8String     endif   Next  I switch logging on or off    ifdef DEBUG  define LOG CATEGORY DETAIL   comment out to turn all conditional logging off while keeping other DEBUG features  endif   In the main block  define various categories corresponding to modules in your app  Also define a logging level  above which logging calls won t be called  Then define various flavours of NSLog output   ifdef LOG CATEGORY DETAIL        define the categories using bitwise leftshift operators      define kLogGCD  1 lt  lt 0       define kLogCoreCreate  1 lt  lt 1       define kLogModel  1 lt  lt 2       define kLogVC  1 lt  lt 3       define kLogFile  1 lt  lt 4        etc        add the categories that should be logged         define kLOGIFcategory kLogModel kLogVC kLogCoreCreate           and the maximum detailLevel to report  use -1 to override the category switch       define kLOGIFdetailLTEQ 4         output looks like this  - AppDelegate myMethod  log string             define myLog category detailLevel format       if detailLevel lt 0      category amp kLOGIFcategory  amp  amp detailLevel lt   kLOGIFdetailLTEQ    NSLog     s   format     PRETTY FUNCTION        VA ARGS              output also shows line number  - AppDelegate myMethod  l17   log string             define myLogLine category detailLevel format       if detailLevel lt 0      category amp kLOGIFcategory  amp  amp detailLevel lt   kLOGIFdetailLTEQ    NSLog     s l i    format     PRETTY FUNCTION     LINE        VA ARGS              output very simple   log string             define myLogSimple category detailLevel format       if detailLevel lt 0      category amp kLOGIFcategory  amp  amp detailLevel lt   kLOGIFdetailLTEQ    NSLog      format       VA ARGS             as myLog but only shows method name   myMethod  log string             Doesn t work in C-functions          define myLog cmd category detailLevel format      if detailLevel lt 0      category amp kLOGIFcategory  amp  amp detailLevel lt   kLOGIFdetailLTEQ    NSLog          format   NSStringFromSelector  cmd       VA ARGS             as myLogLine but only shows method name   myMethod gt l17  log string             define myLog cmdLine category detailLevel format       if detailLevel lt 0      category amp kLOGIFcategory  amp  amp detailLevel lt   kLOGIFdetailLTEQ    NSLog       gt l i    format   NSStringFromSelector  cmd    LINE         VA ARGS             or define your own            define myLogEAGLcontext category detailLevel format       if detailLevel lt 0      category amp kLOGIFcategory  amp  amp detailLevel lt   kLOGIFdetailLTEQ    NSLog     s gt l i  ctx      format     PRETTY FUNCTION     LINE     EAGLContext currentContext       VA ARGS        else         define myLog cmd              define myLog cmdLine              define myLog              define myLogLine              define myLogSimple                define myLogEAGLcontext       endif   Thus  with current settings for kLOGIFcategory and kLOGIFdetailLTEQ  a call like   myLogLine kLogVC  2        self     will print but this won t  myLogLine kLogGCD  2        self    GCD not being printed   nor will  myLogLine kLogGCD  12        self    level too high   If you want to override the settings for an individual log call  use a negative level   myLogLine kLogGCD  -2        self    now printed even tho  GCD category not active    I find the few extra characters of typing each line are worth as I can then   Switch an entire category of comment on or off  e g  only report those calls marked Model  report on fine detail with higher level numbers or just the most important calls marked with lower numbers   I m sure many will find this a bit of an overkill  but just in case someone finds it suits their purposes

User · Answer

My answer to this question might help  looks like it s similar to the one Diederik cooked up  You may also want to replace the call to NSLog   with a static instance of your own custom logging class  that way you can add a priority flag for debug warning error messages  send messages to a file or database as well as the console  or pretty much whatever else you can think of    define DEBUG MODE   ifdef DEBUG MODE      define DebugLog  s        NSLog     lt  p      d  gt       self                   NSString stringWithUTF8String   FILE    lastPathComponent                    LINE                    NSString stringWithFormat  s                      VA ARGS       else      define DebugLog  s          endif

User · Answer

New addition to DLog  Instead of totally removing debug from released application  only disable it  When user has problems  which would require debugging  just tell how to enable debug in released application and request log data via email   Short version  create global variable  yes  lazy and simple solution  and modify DLog like this   BOOL myDebugEnabled   FALSE   define DLog fmt       if  myDebugEnabled  NSLog     s  Line  d    fmt     PRETTY FUNCTION      LINE        VA ARGS       Longer answer at Jomnius iLessons iLearned  How to Do Dynamic Debug Logging in Released Application

User · Answer

Here one big collection of debug constants that we use  Enjoy      Uncomment the defitions to show additional info        define DEBUG       define DEBUGWHERE SHOWFULLINFO       define DEBUG SHOWLINES      define DEBUG SHOWFULLPATH      define DEBUG SHOWSEPARATORS      define DEBUG SHOWFULLINFO      Definition of DEBUG functions  Only work if DEBUG is defined   ifdef DEBUG        define debug separator   NSLog    ----------------------------------------------------------------------------           ifdef DEBUG SHOWSEPARATORS          define debug showSeparators   debug separator         else          define debug showSeparators        endif                                      ifdef DEBUG SHOWFULLPATH          define debug whereFull   debug showSeparators    NSLog   Line  d    s    s     LINE     FILE     FUNCTION     debug showSeparators          else          define debug whereFull   debug showSeparators    NSLog   Line  d    s    s     LINE          NSString alloc  initWithBytes   FILE   length strlen   FILE    encoding NSUTF8StringEncoding  lastPathComponent  UTF8String      FUNCTION     debug showSeparators          endif                                      define debugExt args      debug separator    debug whereFull    NSLog  args      VA ARGS     debug separator                                  Debug Print Macros       ifdef DEBUG SHOWFULLINFO          define debug args      debugExt args      VA ARGS          else          ifdef DEBUG SHOWLINES              define debug args      debug showSeparators    NSLog   NSString stringWithFormat   Line  d          LINE    args        VA ARGS     debug showSeparators             else              define debug args      debug showSeparators    NSLog args      VA ARGS     debug showSeparators             endif      endif                               Debug Specific Types       define debug object  arg   debug    Object       arg         define debug int  arg   debug    integer   i   arg         define debug float  arg   debug    float   f   arg         define debug rect  arg   debug    CGRect    f   f   f   f    arg origin x  arg origin y  arg size width  arg size height         define debug point  arg   debug    CGPoint    f   f     arg x  arg y         define debug bool  arg     debug    Boolean         arg    YES     YES      NO                                     Debug Where Macros       ifdef DEBUGWHERE SHOWFULLINFO          define debug where   debug whereFull          else          define debug where   debug    s    FUNCTION           endif       define debug where separators   debug separator    debug where    debug separator                                    else      define debug args            define debug separator          define debug where           define debug where separators          define debug whereFull           define debugExt args           define debug object  arg         define debug int  arg         define debug rect  arg           define debug bool  arg           define debug point  arg        define debug float  arg    endif

User · Answer

It is simple for Example     - void applicationWillEnterForeground  UIApplication   application        NSLog    s     PRETTY FUNCTION               Output  - AppDelegate applicationWillEnterForeground

[objective-c] How to print out the method name and line number and conditionally disable NSLog?

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