gistfile1.txt

some macros:

#define SGAM_ERROR_MESSAGE(condition, message) \
  do { \
    if (!(condition)) { \
      SGAMError *__error__ = [[SGAMError alloc] initWithMesage:message \
                                                         asset:asset_ \
                                                          file:__FILE__ \
                                                    lineNumber:__LINE__]; \
      return [__error__ autorelease]; \
    } \
  } while (0)

#define SGAM_ERROR_ERROR(condition, err) \
  do { \
    if (!(condition)) { \
      SGAMError *__error__ = [[SGAMError alloc] initWithError:err \
                                                        asset:asset_ \
                                                         file:__FILE__ \
                                                   lineNumber:__LINE__]; \
      return [__error__ autorelease]; \
    } \
  } while (0)


how they are used:


- (SGAMError *)amMain {
  SGAM_ERROR_MESSAGE(destination_ && alAsset_ && thumbDestination_,
                     @"nil argument");

  SGAM_CHECK_CANCEL();

  // If it exists, remove the file on disk that exists at our destination path.
  BOOL exists = [fileManager_ fileExistsAtPath:[destination_ path]];
  if (exists) {
    NSError *error = NULL;
    BOOL success = [fileManager_ removeItemAtURL:destination_ error:&error];
    SGAM_ERROR_ERROR(success, error);
  }

  // Save the full resolution image.
  ALAssetRepresentation *rep = [alAsset_ defaultRepresentation];
  SGAM_ERROR_MESSAGE(rep, @"nil rep");
  CGImageRef img = [rep fullResolutionImage];
  SGAM_ERROR_MESSAGE(img, @"nil img");
  UIImage *sourceImg = 
    [UIImage imageWithCGImage:img
                        scale:rep.scale
                  orientation:(UIImageOrientation)rep.orientation];
  SGAM_ERROR_MESSAGE(sourceImg, @"nil sourceImg");

  ... etc ...
}