GDataServiceGooglePicasaWeb* service =
 [[GDataServiceGooglePicasaWeb alloc] init];

[service setUserCredentialsWithUsername:@"my.account@gmail.com"
 password:@"mypasswd"];

// get the URL for the album
NSURL *albumURL = [GDataServiceGooglePicasaWeb
 picasaWebFeedURLForUserID:@"my.account" albumID:nil
 albumName:@"MyBestPhotos" photoID:nil kind:nil access:nil];

// set a title and description for the new photo
GDataTextConstruct *title, *desc;
title = [GDataTextConstruct textConstructWithString:@"Sunset Photo"];
desc = [GDataTextConstruct textConstructWithString:@"A nice day"];

GDataEntryPhoto *newPhoto = [GDataEntryPhoto photoEntry];
[newPhoto setTitle:title];
[newPhoto setPhotoDescription:desc];

// attach the photo data
NSData *data = [NSData dataWithContentsOfFile:@"/SunsetPhoto.jpg"];
[newPhoto setPhotoData:data];
[newPhoto setPhotoMIMEType:@"image/jpeg"];

// now upload it
GDataServiceTicket *ticket;
ticket = [service fetchPicasaWebEntryByInsertingEntry:newPhoto
 forFeedURL:albumURL
 delegate:self
 didFinishSelector:@selector(addPhotoTicket:finishedWithEntry:)
 didFailSelector:@selector(addPhotoTicket:failedWithError:)];

#import "GData/GData.h"

GDataServiceGoogleCalendar *service =
  [[GDataServiceGoogleCalendar alloc] init];
[service setUserCredentialsWithUsername:@"myaccount@gmail.com"     
                               password:@"mypassword"];

NSURL *calendarFeedURL =
  [NSURL URLWithString:kGDataGoogleCalendarDefaultPrivateFullFeed];

GDataEntryCalendarEvent *newEvent =
  [GDataEntryCalendarEvent calendarEvent];
GDataTextConstruct *content =
  [GDataTextConstruct textConstructWithString:@"Battle today at 10pm"];

[newEvent setContent:content];
[newEvent setIsQuickAdd:YES];

[service fetchCalendarEventByInsertingEntry:newEvent
                         forFeedURL:calendarFeedURL
                           delegate:self
        didFinishSelector:@selector(calendarTicket:finishedWithEntry:)
          didFailSelector:@selector(calendarTicket:failedWithError:)];

NSURL *baseFeedURL = [NSURL URLWithString:kGDataGoogleBaseUserItemsFeed];
[service fetchGoogleBaseFeedWithURL:baseFeedURL                 
                     delegate:self
            didFinishSelector:@selector(baseTicket:finishedWithFeed:)    
              didFailSelector:@selector(baseTicket:failedWithError:)];

- (void)baseTicket:(GDataServiceTicket*)ticket
  finishedWithFeed:(GDataFeedGoogleBase *)feed {
  NSArray *myItems = [feed entries];
}

1. A file owned by UID 99 appears to be owned by whoever is viewing it (but see the caveat below).
2. Volumes mounted with the MNT_IGNORE_OWNERSHIP flag treat all files as if they were owned by UID 99.

$ touch file.txt
$ ls -l file.txt
-rw-r--r-- 1 jgm jgm 0 Mar 9 22:07 file.txt

$ sudo chown 99:99 file.txt
$ ls -l file.txt
-rw-r--r-- 1 jgm jgm 0 Mar 9 22:07 file.txt 

$ sudo ls -l file.txt
-rw-r--r-- 1 unknown unknown 0 Mar 9 22:07 file.txt

$ sudo -u test ls -l file.txt
-rw-r--r-- 1 test test 0 Mar 9 22:07 file.txt

int
  vnode_getattr(...) {
  ...

  if ((nuid == 99) && !vfs_context_issuser(ctx))
    nuid = kauth_cred_getuid(vfs_context_ucred(ctx));
  ...
}

$ cat mnt_ownership.c
#include <stdio.h>
#include <sys/param.h>
#include <sys/mount.h>

int
main(int argc, char **argv) {
  struct statfs sb;
  int ignore_flag;

  /* argv[1] is path to the volume or a file/folder within */
  statfs(argv[1], &sb);
  ignore_flag = (sb.f_flags & MNT_IGNORE_OWNERSHIP);
  printf("ownership %s\n", ignore_flag ? "ignored" : "enabled");
  return 0;
}

$ gcc -o mnt_ownership mnt_ownership.c -Wall
$ ./mnt_ownership /Volumes/TINY
ownership ignored

$ cd /Volumes/TINY
$ ls -l
total 16
drwxrwxrwx 1 jgm jgm 8192 Jan 27 14:12 iPod_Control/

$ sudo ls -l
total 16
drwxrwxrwx 1 unknown unknown 8192 Jan 27 14:12 iPod_Control

$ touch file.txt
$ ls -l file.txt 
-rwxrwxrwx 1 jgm jgm 0 Mar 10 16:27 file.txt

$ sudo ls -l file.txt
-rwxrwxrwx 1 unknown unknown 0 Mar 10 16:27 file.txt

int
vnode_getattr(...) {
  ...

  /*
   * Handle uid/gid == 99 and MNT_IGNORE_OWNERSHIP here.
   */
  ...
  if (vp->v_mount->mnt_flag & MNT_IGNORE_OWNERSHIP) {
    nuid = vp->v_mount->mnt_fsowner;
    if (nuid == KAUTH_UID_NONE)
      nuid = 99;
  ...
  }


  if ((nuid == 99) && !vfs_context_issuser(ctx))
    nuid = kauth_cred_getuid(vfs_context_ucred(ctx));
  ...
}

• One of the great features of MacFUSE is the large set of language bindings available to programmers who want to write file systems. Now the MacFUSE website has an Objective-C library that's going to be especially popular with all you Cocoa programmers. Like MacFUSE itself, this library is open source so you can extend it to your heart's content. Note that this is the very same library that was used to create the MacFUSE demos shown during Macworld Expo 2007.
• By popular demand, you can now get source code for the Spotlight file system that was presented as a demo of what you can do with MacFUSE.
• For those of you wondering what MacFUSE is and what you can do with it, check out this article I wrote that appears on O'Reilly's MacDevCenter.

• A virtual file system (VFS) kernel extension
• A special-purpose mount_fusefs program
• A patch to the FUSE user-space library
• A patch to the SSHFS file system

• Usability testing of five or six users tells you all you need. You’re looking for big problems, not statistical significance on the small ones.
• Users want to accomplish their tasks, not use your features ("users care about a lot fewer things than you might think").
• Usability isn’t the same as learnability, and “usability testing” usually tests the latter.
• So what if 30% of users fail to accomplish the task in testing? Those people will ask for help or read the doc, or aren’t your target users, anyway.
• Karen Fries at Microsoft invented the Wizard as a way to teach you how to use the usual UI, not to do the task for you.
• Users don’t read (documentation or dialog instructions).
• Users can’t use the mouse as easily as you think.
• Invent imaginary users, name them, and talk about them to make them seem like real people, which they do represent.
• Icons work well to represent nouns, but not verbs.

1. lazy initialization
2. +initialize
3. +load

1. +load is invoked once per class or category.
2. +load is usually invoked before +initialize, but not always.
3. You can't be sure your superclasses are loaded.
4. You can't be sure any other classes are loaded.
5. You know, you really should be using +initialize.

@implementation Foo(FooBarAdditions)
....
@end

@interface Foo(FooBarAdditionsPrivateMethods)
+ (void)initializeBar;
@end

@implementation Foo(FooBarAdditionsPrivateMethods)
+ (void)initializeBar {
// Initialize stuff here
}
@end

void __attribute__ ((constructor)) InitializeFooBar(void) {
static BOOL wasInitialized = NO; 
  if (!wasInitialized) {    
// safety in case we get called twice.
    [Foo initializeBar];
    wasInitialized = YES;
  }
}

+(id)fooFerBar:(id)bar {
   static NSDictionary *foo = [NSDictionary dictionaryWithObjects:...];
   return [foo objectWithKey:bar];
}

cxa_guard_acquire

my actual code

cxa_guard_release
cxa_guard_abort
Unwind_Resume
...

+(id)fooFerBar:(id)bar {
@synchronized(self) {
   static NSDictionary *foo = [NSDictionary dictionaryWithObjects:...];
   return [foo objectWithKey:bar];
}
}

...
objc_sync_enter
objc_exception_try_enter
setjmp
objc_exception_extract
cxa_guard_acquire

my actual code

cxa_guard_release
cxa_guard_abort
objc_exception_try_exit
objc_sync_exit
objc_exception_throw
...

static NSDictionary *foo = nil;

+(id)fooFerBar:(id)bar {
@synchronized(self) {
   if (!foo) foo = [NSDictionary dictionaryWithObjects:...];
   ReplaceMethodImplementationWithSelector
      ([self class], @selector(fooFerBar), @selector(fooFerBar2));
}
   return [foo objectWithKey:bar];
}

+(id)fooFerBar2:(id)bar {
   return [foo objectWithKey:bar];
}

+(id)fooFerBar:(id)bar {
@synchronized(self) {
   static NSDictionary *foo = nil;
   if (!foo) foo = [NSDictionary dictionaryWithObjects:...];
}
   return [foo objectWithKey:bar];
}

#include <pthread.h>

+(id)fooFerBar:(id)bar {
   static pthread_mutex_t mtx = PTHREAD_MUTEX_INITIALIZER;
   if (pthread_mutex_lock(&mtx)) {
      printf("lock failed sigh...");
      exit(-1);
}
   static NSDictionary *foo = nil;
   if (!foo) foo = [NSDictionary dictionaryWithObjects:...];
   if (pthread_mutex_unlock(&mtx) != 0)) {
      printf("unlock failed sigh...");
      exit(-1);
}
   return [foo objectWithKey:bar];
}