gistfile1.m

typedef void(^LogBlock)(NSString *, ...);
#define LogBlock LogBlock NS_FORMAT_FUNCTION(1,2)

- (BOOL)loggingErrorsDo:(void (^)(LogBlock error))block
{
  __block BOOL success = YES;
  block(^(NSString *messageFormat, ...) {
    va_list args;
    va_start(args, messageFormat);
    NSString *message = [[NSString alloc] initWithFormat:messageFormat arguments:args];
    va_end(args);
    DLog(@"%@", message);
    success = NO;
  });
  return success;
}


// Usage
- (BOOL)createAndSaveThingyWithName:(NSString *)name
{
  return [self loggingErrorsDo:^(LogBlock err) {
    Thingy *thingy = [[Thingy alloc] initWithFluxCapacitor:self.fluxCapacitor];
    if (!thingy) return err(@"cannot create thingy with flux capacitor: %@", self.fluxCapacitor);
    NSError *error;
    if (![thingy setValue:name forProperty:kThingyNameProperty error:&error]) 
      return err(@"error setting thingy name %@: %@", name, error);
    if (![self.repo addRecord:thingy error:&error]) 
      return err(@"error adding thingy %@ to repo: %@", thingy, error);
    if (![self.repo saveAndReturnError:&error]) 
      return err(@"error saving added thingy %@: %@", thingy, error);
  };
}