"The Most Useful Objective-C Code I’ve Ever Written" Reference: http://vgable.com/blog/2010/08/19/the-most-useful-objective-c-code-ive-ever-written/#Get_LOG_EXPR Easy printing of Obj-C type values

macro.m

#define LOG_EXPR(_X_) do{\
   __typeof__(_X_) _Y_ = (_X_);\
 	const char * _TYPE_CODE_ = @encode(__typeof__(_X_));\
 	NSString *_STR_ = VTPG_DDToStringFromTypeAndValue(_TYPE_CODE_, &_Y_);\
 	if(_STR_)\
 		NSLog(@"%s = %@", #_X_, _STR_);\
 	else\
 		NSLog(@"Unknown _TYPE_CODE_: %s for expression %s in function %s, file %s, line %d", _TYPE_CODE_, #_X_, __func__, __FILE__, __LINE__);\
 } while(0)

VTPG_Common.h

#pragma once
// Copyright (c) 2008-2010, Vincent Gable.
// [email protected]

//based off of http://www.dribin.org/dave/blog/archives/2008/09/22/convert_to_nsstring/
NSString * VTPG_DDToStringFromTypeAndValue(const char * typeCode, void * value);

// WARNING: if NO_LOG_MACROS is #define-ed, than THE ARGUMENT WILL NOT BE EVALUATED
#ifndef NO_LOG_MACROS


#define LOG_EXPR(_X_) do{\
  __typeof__(_X_) _Y_ = (_X_);\
	const char * _TYPE_CODE_ = @encode(__typeof__(_X_));\
	NSString *_STR_ = VTPG_DDToStringFromTypeAndValue(_TYPE_CODE_, &_Y_);\
	if(_STR_)\
		NSLog(@"%s = %@", #_X_, _STR_);\
	else\
		NSLog(@"Unknown _TYPE_CODE_: %s for expression %s in function %s, file %s, line %d", _TYPE_CODE_, #_X_, __func__, __FILE__, __LINE__);\
}while(0)

#define LOG_NS(...) NSLog(__VA_ARGS__)
#define LOG_FUNCTION()	NSLog(@"%s", __func__)

#else /* NO_LOG_MACROS */

#define LOG_EXPR(_X_)
#define LOG_NS(...)
#define LOG_FUNCTION()
#endif /* NO_LOG_MACROS */



// http://www.wilshipley.com/blog/2005/10/pimp-my-code-interlude-free-code.html
static inline BOOL IsEmpty(id thing) {
	return thing == nil ||
			([thing respondsToSelector:@selector(length)] && [(NSData *)thing length] == 0) ||
			([thing respondsToSelector:@selector(count)]  && [(NSArray *)thing count] == 0);
}

VTPG_Common.m

#import "VTPG_Common.h"
// Copyright (c) 2008-2010, Vincent Gable.
// http://vincentgable.com
//
//based off http://www.dribin.org/dave/blog/archives/2008/09/22/convert_to_nsstring/
//
static BOOL TypeCodeIsCharArray(const char *typeCode){
    size_t len = strlen(typeCode);
    if(len <= 2)
        return NO;
  size_t lastCharOffset = len - 1;
	size_t secondToLastCharOffset = lastCharOffset - 1 ;
	
	BOOL isCharArray = typeCode[0] == '[' &&
						typeCode[secondToLastCharOffset] == 'c' && typeCode[lastCharOffset] == ']';
	for(int i = 1; i < secondToLastCharOffset; i++)
		isCharArray = isCharArray && isdigit(typeCode[i]);
	return isCharArray;
}

//since BOOL is #defined as a signed char, we treat the value as
//a BOOL if it is exactly YES or NO, and a char otherwise.
static NSString* VTPGStringFromBoolOrCharValue(BOOL boolOrCharvalue) {
	if(boolOrCharvalue == YES)
		return @"YES";
	if(boolOrCharvalue == NO)
		return @"NO";
	return [NSString stringWithFormat:@"'%c'", boolOrCharvalue];
}

static NSString *VTPGStringFromFourCharCodeOrUnsignedInt32(FourCharCode fourcc) {
	return [NSString stringWithFormat:@"%u ('%c%c%c%c')",
										fourcc,
										(fourcc >> 24) & 0xFF,
										(fourcc >> 16) & 0xFF,
										(fourcc >> 8) & 0xFF,
										fourcc & 0xFF];
}

static NSString *StringFromNSDecimalWithCurrentLocal(NSDecimal dcm) {
	return NSDecimalString(&dcm, [NSLocale currentLocale]);						   
}

NSString * VTPG_DDToStringFromTypeAndValue(const char * typeCode, void * value) {
	#define IF_TYPE_MATCHES_INTERPRET_WITH(typeToMatch,func) \
		if (strcmp(typeCode, @encode(typeToMatch)) == 0) \
			return (func)(*(typeToMatch*)value)

#if	TARGET_OS_IPHONE
	IF_TYPE_MATCHES_INTERPRET_WITH(CGPoint,NSStringFromCGPoint);
	IF_TYPE_MATCHES_INTERPRET_WITH(CGSize,NSStringFromCGSize);
	IF_TYPE_MATCHES_INTERPRET_WITH(CGRect,NSStringFromCGRect);
#else
	IF_TYPE_MATCHES_INTERPRET_WITH(NSPoint,NSStringFromPoint);
	IF_TYPE_MATCHES_INTERPRET_WITH(NSSize,NSStringFromSize);
	IF_TYPE_MATCHES_INTERPRET_WITH(NSRect,NSStringFromRect);
#endif
	IF_TYPE_MATCHES_INTERPRET_WITH(NSRange,NSStringFromRange);
	IF_TYPE_MATCHES_INTERPRET_WITH(Class,NSStringFromClass);
	IF_TYPE_MATCHES_INTERPRET_WITH(SEL,NSStringFromSelector);
	IF_TYPE_MATCHES_INTERPRET_WITH(BOOL,VTPGStringFromBoolOrCharValue);
	IF_TYPE_MATCHES_INTERPRET_WITH(NSDecimal,StringFromNSDecimalWithCurrentLocal);
	
	#define IF_TYPE_MATCHES_INTERPRET_WITH_FORMAT(typeToMatch,formatString) \
		if (strcmp(typeCode, @encode(typeToMatch)) == 0) \
			return [NSString stringWithFormat:(formatString), (*(typeToMatch*)value)]
	
	
	IF_TYPE_MATCHES_INTERPRET_WITH_FORMAT(CFStringRef,@"%@"); //CFStringRef is toll-free bridged to NSString*
	IF_TYPE_MATCHES_INTERPRET_WITH_FORMAT(CFArrayRef,@"%@"); //CFArrayRef is toll-free bridged to NSArray*
	IF_TYPE_MATCHES_INTERPRET_WITH(FourCharCode, VTPGStringFromFourCharCodeOrUnsignedInt32);
	IF_TYPE_MATCHES_INTERPRET_WITH_FORMAT(long long,@"%lld");
	IF_TYPE_MATCHES_INTERPRET_WITH_FORMAT(unsigned long long,@"%llu");
	IF_TYPE_MATCHES_INTERPRET_WITH_FORMAT(float,@"%f");
	IF_TYPE_MATCHES_INTERPRET_WITH_FORMAT(double,@"%f");
#if __has_feature(objc_arc)
	IF_TYPE_MATCHES_INTERPRET_WITH_FORMAT(__unsafe_unretained id,@"%@");
#else /* not __has_feature(objc_arc) */
    IF_TYPE_MATCHES_INTERPRET_WITH_FORMAT(id,@"%@");
#endif
	IF_TYPE_MATCHES_INTERPRET_WITH_FORMAT(short,@"%hi");
	IF_TYPE_MATCHES_INTERPRET_WITH_FORMAT(unsigned short,@"%hu");
	IF_TYPE_MATCHES_INTERPRET_WITH_FORMAT(int,@"%i");
	IF_TYPE_MATCHES_INTERPRET_WITH_FORMAT(unsigned, @"%u");
	IF_TYPE_MATCHES_INTERPRET_WITH_FORMAT(long,@"%i");
	IF_TYPE_MATCHES_INTERPRET_WITH_FORMAT(long double,@"%Lf"); //WARNING on older versions of OS X, @encode(long double) == @encode(double)
	
	//C-strings
	IF_TYPE_MATCHES_INTERPRET_WITH_FORMAT(char*, @"%s");
	IF_TYPE_MATCHES_INTERPRET_WITH_FORMAT(const char*, @"%s");
	if(TypeCodeIsCharArray(typeCode))
		return [NSString stringWithFormat:@"%s", (char*)value];
	
	IF_TYPE_MATCHES_INTERPRET_WITH_FORMAT(void*,@"(void*)%p");
	
	//This is a hack to print out CLLocationCoordinate2D, without needing to #import <CoreLocation/CoreLocation.h>
	//A CLLocationCoordinate2D is a struct made up of 2 doubles.
	//We detect it by hard-coding the result of @encode(CLLocationCoordinate2D).
	//We get at the fields by treating it like an array of doubles, which it is identical to in memory.
	if(strcmp(typeCode, "{?=dd}")==0)//@encode(CLLocationCoordinate2D)
		return [NSString stringWithFormat:@"{latitude=%g,longitude=%g}",((double*)value)[0],((double*)value)[1]];
	
	//we don't know how to convert this typecode into an NSString
	return nil;
}