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What unique uses of NSLog have you used?

Do you have unique or special NSLog applications that you are using for debugging?

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5 answers


I like to use this format for debugging.

NSLog( @"<%p %@:(%d)> %@", self, [[NSString stringWithUTF8String:__FILE__] lastPathComponent], __LINE__, [NSString stringWithFormat:(s), ##__VA_ARGS__] )

Of course, you will want to wrap this in your own method or function for ease of use. I use a preprocessor and also only allow it for my own use and special assemblies that I send to beta testers. This, by the way, is copied from my answer to this question.



#define DEBUG_MODE

#ifdef DEBUG_MODE
    #define DebugLog( s, ... ) NSLog( @"<%p %@:(%d)> %@", self, [[NSString stringWithUTF8String:__FILE__] lastPathComponent], __LINE__, [NSString stringWithFormat:(s), ##__VA_ARGS__] )
#else
    #define DebugLog( s, ... ) 
#endif

This does DebugLog

the same thing as it does NSLog

, but displays the filename and line number at which it was called:

2009-05-23 17:23:40.920 myproject[92523:10b] <AppCon.m:(8)> My debug message...
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I am using some macros with NSLog to quickly debug the contents of cocoa NSPoint

, NSSize

and NSRect

structs:

#define LogPoint(POINT) CMLog(@"%s: (%0.0f, %0.0f)",\
                              #POINT, POINT.x, POINT.y)

#define LogSize(SIZE) CMLog(@"%s: %0.0f x %0.0f",\
                            #SIZE, SIZE.width, SIZE.height)

#define LogRect(RECT) CMLog(@"%s: (%0.0f, %0.0f) %0.0f x %0.0f",\
                            #RECT, RECT.origin.x, RECT.origin.y,\
                            RECT.size.width, RECT.size.height)

They can be used as follows:



LogPoint(somePoint);
LogSize(someSize);
LogRect(someRect);

And they produce the following output:

somePoint: (100, 200)
someSize: 12 x 440
someRect: (120, 240) 326 x 74
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NSLog(@"%s", __func__);

prints the current signature or function name.

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This is not an NSLog function, however it is very handy for use with NSLog: you can use% @placeholder on objects and their descriptions will be displayed:

NSLog (@"The object is %@", someKindOfObjectWhichYouWantToDisplay);

This way you can, for example, see what kind of object you get for example. This works by sending a "description" to the object selector, which of course can be implemented in your own objects.

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Here's how you can separate some parts of the debug logs to make them more readable:

// MyDebugStuff.h:
void MyLog_Indent();
void MyLog_Outdent();
void MyLog(NSString * format, ...);

// MyDebugStuff.m:
int logIndentLevel = 0;

void MyLog_Indent()  { logIndentLevel++; }
void MyLog_Outdent() { if (logIndentLevel > 0) { logIndentLevel--; } }

void MyLog(NSString * format, ...)
{
    va_list args;
    va_start(args, format);

    NSString * indentString = [[NSString stringWithString:@""]
                     stringByPaddingToLength:(2*LogIndentLevel)
                                  withString:@" "
                             startingAtIndex:0];

    NSLogv([NSString stringWithFormat:@"%@%@", indentString, format], args);

    va_end(args);
}

It can be used like this:

MyLog(@"Hello, world");
MyLog_Indent();
MyLog(@"Step 1");
MyLog(@"Step 2");
MyLog_Indent();
MyLog(@"Step 2a");
MyLog(@"Step 2b");
MyLog_Outdent();
MyLog(@"Step 3");
MyLog_Outdent();
MyLog(@"Goodbye, cruel world!");

And will produce:

Hello, world
  Step 1
  Step 2
    Step 2a
    Step 2b
  Step 3
Goodbye, cruel world!
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