* Updated on 28 November 2011 for Xcode 4.2
I am a newcomer to the
Xcode and I decided to check the debug means. Basically, I was looking for a macro to dump line number, file name and function name along with some output. However, I found only some "simple" debug classes. I think debug output should be done by macros. I checked the Apple documentation and found an interesting topic:
Variadic Macros. They are introduced by the
C99 standard. After a few attempts I decided that the following macro is good enough for me:
//
// dbg.h
//
// Created by oguz.kupusoglu@gmail.com on 15/2/2009.
// Copyright 2009 Oguz Kupusoglu. All rights reserved.
//
#ifdef DEBUG
#define DBG(format, ...) NSLog(@"%d,%s,"format,__LINE__,__FUNCTION__,##__VA_ARGS__);
#define DBG_CALLED DBG("called")
#else
#define DBG(format, ...)
#define DBG_CALLED
#endif
#define LOG(format, ...) NSLog(@"%d,%s,"format,__LINE__,__FUNCTION__,##__VA_ARGS__);
#define LOG_CALLED LOG("called")
Note that DBG_CALLED is a helper define which is useful for following the callstack. I ignored the file name, i.e. __FILE__, as the method name being in the [class method] format gives a hint of the file in question due to naming files after the class names convention. Certainly one can add __FILE__ at the expense of extra overhead. Sample usage and output as received from the
Console which is accessed from the
"View/Debug Area/Activate Console" option of the Xcode are below:
-(void) viewWillAppear:(BOOL)animated
{
DBG_CALLED
DBG("view
frame\n"
"origin x:|%.0f|
y:|%.0f|\n"
"width:|%.0f|
height:|%.0f|\n",
self.view.frame.origin.x, self.view.frame.origin.y,
self.view.frame.size.width, self.view.frame.size.height)
DBG("year:|%d|",
2009)
DBG("updated")
[super viewWillAppear:animated];
}
...] 69,-[MyViewController
viewWillAppear:],called
...] 75,-[MyViewController viewWillAppear:],view frame
origin x:|0| y:|20|
width:|768| height:|1004|
...] 77,-[MyViewController viewWillAppear:],year:|2009|
...] 79,-[MyViewController viewWillAppear:],updated
Note that the DEBUG define is set
via the
"PROJECT/Build Settings" option. Go to
"... Preprocessing" section and add the define "DEBUG" to the
"Debug" subsection.
Finally, I think
"Product/Generate Output\Generate Preprocessed File" is a good option as it gives the preprocessor output of the selected file. For example the above DBG() macros are expanded as below:
-(void) viewWillAppear:(BOOL)animated
{
NSLog(@"%d,%s,""called",69,__FUNCTION__);
NSLog(@"%d,%s,""view frame\n" "origin x:|%.0f|
y:|%.0f|\n" "width:|%.0f| height:|%.0f|\n",75,__FUNCTION__, self.view.frame.origin.x,
self.view.frame.origin.y, self.view.frame.size.width,
self.view.frame.size.height);
NSLog(@"%d,%s,""year:|%d|",77,__FUNCTION__, 2009);
NSLog(@"%d,%s,""updated",79,__FUNCTION__);
[super
viewWillAppear:animated];
}
Note that when there is no variable argument,
"##" removes the trailing comma! Just excellent...
