Enable and Disable NSLog in DEBUG mode

objective-c cocoa nslog

I want to enable NSLog when I am in debug and disable it otherwise. A very simple thing is:

#ifdef DEBUG
NSLog(@"My log");
#endif

But all this #ifdef and #endif is borring... :( So I try other thing: (.pch is good place to put it)

#ifdef DEBUG
#   define NSLog(text) NSLog(text);
#else 
#   define NSLog(text) 
#endif

This work very fine (isn't recursive). But the problem is that NSLog have infinite arguments.

void NSLog(NSString *format, ...)

How I solve this to work in preprocessor mode?

-- Edit --

This code make your NSLog better:

#ifdef DEBUG
    #define NSLog(FORMAT, ...) fprintf(stderr,"%s\n", [[NSString stringWithFormat:FORMAT, ##__VA_ARGS__] UTF8String]);
#else
    #define NSLog(...)
#endif

+1 for Nice Question. A complete reusable component on this topic at mobile.tutsplus.com/tutorials/iphone/…

I follow the guide in the link. But I got the following compile error: Undefined symbols for architecture x86_64: ld: symbol(s) not found for architecture x86_64 clang: error: linker command failed with exit code 1 (use -v to see invocation) Please help @MahbuburRAaman

@Gon, Error Undefined symbols for architecture x86_64: ld: symbol(s) not found for architecture x86_64 appears for several reason. For example, for missing library or other cases, have a look at the following SO resource stackoverflow.com/questions/18408531/…, stackoverflow.com/questions/11996227/… , stackoverflow.com/questions/6231368/….

@MahbuburRAaman Thanks for replying. I've found the reason is I'm calling this custom NSLog method from a objective c++ file.

Please, where have I to place this code?

JustSid

This should do the trick:

 #ifdef DEBUG
 #   define NSLog(...) NSLog(__VA_ARGS__)
 #else 
 #   define NSLog(...) (void)0
 #endif

It's fine but replace # define NSLog(...) NSLog(VA_ARGS); with # define NSLog(...) NSLog(VA_ARGS) (remove last ;)

@JustSid: How do I set or reset the DEBUG flag?

This doesn't play nice with the ternary operator.

@StianHøiland While it's questionable wether ternary operator around void is a good idea to begin with, I've updated the code so that it does support it.

Aram Kocharyan

This is a bit shorter and also disables NSLog when using a device. If you're writing a game, NSLogs sent often can reduce your FPS from 60 to 20.

#if !defined(DEBUG) || !(TARGET_IPHONE_SIMULATOR)
    #define NSLog(...)
#endif

NaXir

All the above answers are correct. I can suggest you to do it in a following way also. Suppose i have a if statement with no brackets

if(x==5)
NSLog("x is 5");

What will happen if it will replace NSLog with no statement. So we can simply replace it with an empty loop.

#ifdef DEBUG
#define NSLog(...) NSLog(__VA_ARGS__)
#else
#define NSLog(...) do {} while (0)
#endif

This statement will run an empty loop once. This will safely remove your NSLog from all of your live code.

Good point, and that’s also a good place to repeat that using if statements without brackets is probably a bad idea in the first place.

the code will be preprocessed to if (x==5) ; which is fine.

This doesn't play nice with the ternary operator.

if you have a common constants file that is included in .pch then place in that, otherwise you can place it at top of class before @implementation

Prashant

#ifndef Debug
    #define Debug 1
#endif

#if Debug
#   define DebugLog(fmt, ...) NSLog((@"%s [Line %d] " fmt), __PRETTY_FUNCTION__, __LINE__, ##__VA_ARGS__);
#else
#   define DebugLog(...)
#endif

Set Debug to 1 for enabling the log and 0 for disabling it.

You can create Constant Header file and add the code to it and for accessing you just need to the import the Header file and use the DebugLog function to log the variables you desire to....

Canea Rowan

Here is a nice trick... add to any .m

#define EXTRANSLog if([[NSUserDefaults standardUserDefaults] boolForKey:@"SomeFancyKey"] == YES) NSLog

Replace any

NSLog(@"????");

with

EXTRANSLog(@"????");

In this example, I created a NSUser key and set the BOOL to YES,, use some form of switch etc to change the key to NO or remove altogether if you don't want to view the EXTRANSLog's via console debugger.

I use this when troubleshooting and don't want all the excessive logs to appear. Only when SomeFancyKey == YES.

This is the same as

#define NSLog if(1) NSLog

where 1 is YES show NSLog, and 0 is NO.

Enable and Disable NSLog in DEBUG mode

Follow WeChat

Want to stay one step ahead of the latest teleworks?

相似问题

Platform

Support

Links

Contact US