Generally helpful macros I like to include in all my projects

HelpfulMacros.h

//
//  HelpfulMacros.h
//
//  Created by Jim Kubicek on 4/19/11.
//  Copyright 2011 Jim Kubicek. All rights reserved.
//

// Logging
//   Based on code from http://cocoaheads.byu.edu/node/6

static inline void QuietLog (NSString *format, ...) {
    if (format == nil) {
        printf("nil\n");
        return;
    }
    // Get a reference to the arguments that follow the format parameter
    va_list argList;
    va_start(argList, format);
    // Perform format string argument substitution, reinstate %% escapes, then print
    NSString *s = [[NSString alloc] initWithFormat:format arguments:argList];
    printf("%s\n", [[s stringByReplacingOccurrencesOfString:@"%%" withString:@"%%%%"] UTF8String]);
    va_end(argList);
}

#ifndef LocationLog
#define LocationLog(format,...) do {\
    { \
        NSString *file = [[NSString stringWithUTF8String:__FILE__] lastPathComponent]; \
        printf("%s:%d - ", [file UTF8String], __LINE__); \
        QuietLog((format),##__VA_ARGS__); \
    }\
    } while(0)
#endif

// Error checking
#define LOG_ERROR_IF_FALSE_OR_NULL(x) if(!x) LocationLog(@"%@", error)

// Check to see if an object is empty or null
// http://blog.wilshipley.com/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);
}