Today’s task is getting Xcode working with a remote Git repository, so that I can collaborate with others – and use a laptop and a desktop to program.

  • The instructions on are good, and I used them to set up a new username, SSH key, and a repository for a free open-source account.
  • I then followed the instructions at “Xcode 4 and Git for newbies“, which are also good.  The main things to keep in mind seem to be:
    • in Xcode, to set up the repository in the Organizer, you need to press the little plus button at the bottom of the list on the left, and then choose the “Checkout or Clone” drop down – not “add a repository”.  The location is<username>/<repository name>.git .
    • Save the project as “origin”, which sets up an “origin” directory.
    • The password Xcode asks for is the pass phrase used earlier.
  • I then created a new Xcode project, and saved it so that it all went into a subdirectory of the origin directory.
  • Then committing and pushing the files worked perfectly, and they showed up in my github repository on the web.

The next step was to checkout the repository with the same username but onto a different computer.  Trying the naive approach – just opening Xcode and following the same series of steps in the Organizer – led me to the error “Authentication failed because the name or password was incorrect.”  The answer was to copy my private and public SSH keys from the first machine to the second, at ~/.ssh/id_rsa*. Note the terminal command “mount” shows the path to any mounted drives, which is helpful for copying.  Once copied, I tested the connection to github in the terminal with ssh -T  This informed me I had the wrong permissions for my private key, which I fixed with a chmod.  Then I tested the ssh connection as described in the github intro with ssh -vT  This did not work the first time without the “v” flag.  For some reason with the “v” it worked, and I was then able to continue in Xcode and connect to the repository.

One other issue when using multiple machines is making sure you export your developer profile from the Xcode Organizer on the original Mac, and import it into the second Mac’s Organizer.

Off to learn about the functional programming language Haskell this evening, to broaden the mind.


Ever deeper into the web

  • I tried putting my locally hosted pages in a subdirectory after all, and they don’t work.  Looks like a detour into mod_rewrite is required.
  • I wanted to add an entry to the user’s calendar using html5.  I found some sample code that uses WAC‘s deviceapis variable, but no information on how to gain access to this. This stack overflow post suggests that there is no way to do it with phone gap (at least as of late 2011), but there is a suggestion of generating an iCalendar file on the fly. And this doesn’t look hard to do, e.g. this stack overflow post and the wikipedia entry explain the format. I find (using my increasingly valuable localhost) that if I just point the browser to a test.ics file, it immediately opens up iCalendar with the new event.  And likewise, if a php script outputs the appropriate format and filename (as per the stack overflow post above). Time zone formatting is discussed here.

Just came across Indie Game: the Movie – I’ll have to go see it!


Time for sound

Time for sound.  In iOS it looks like sound can be played by AVAudioPlayer, and recorded by AVAudioRecorder.  The broader framework is called AVFoundation.  However, at a very low level there is also the Core Audio framework, which includes the Audio Toolbox and Audio Unit frameworks.

There are some great sample projects available at Apple’s Audio & Visual Starting Point:

  • AddMusic shows how to pick songs from the iTunes library.  This also includes setting up an AVAudioSession, which I’m not sure is necessary.
  • avTouch shows how to play sounds using AVAudioPlayer.
  • SpeakHere shows how to record sounds using AQRecord.  On closer inspection this looks extremely daunting.
  • AVAudioRecorder is another approach that looks a lot easier, as documented in this Stack Overflow post, and this Techotopia post.  However, there is a subtlety when you try to play the recorded sound in an AVAudioPlayer – for some reason using
    self.recordingPlayer = [[AVAudioPlayer alloc] 
       initWithContentsOfURL:self.audioRecorder.url error:&error];

    does not ever call the delegate routines when the URL is that of the recorded sound (in either the simulator or the device). So instead, I used

    NSData* recordedData = [NSData 
       dataWithContentsOfFile:[self.audioRecorder.url path]];
    self.recordingPlayer = [[AVAudioPlayer alloc] 
       initWithData:recordedData error:&error];

    - which worked fine.  Another gotcha is to make sure the AVAudioPlayer object is not disposed of at the end of the method, but before the playing actually happens. My solution was to make it an instance variable (as in the sample code above).

  • Audio UI Sounds (SysSound) shows how to play alert sound-effects, but on closer inspection comes with the warning this should not be used for other sound effects, e.g. in games.
  • OpenAL is one solution, with sample code called oalTouch.  This comes with some C code (MyOpenALSupport.c) which looks handy, if a little daunting.  Note that to call this with Automatic Reference Counting (ARC), you need to use (__bridge CFURLRef) and then delete the line CFRelease(fileURL);. I forgot this last part and it took a while to realise what was going on.  There is also a great basic tutorial by Ben Britten.

The Multimedia Programming Guide – Audio has more context.  And as usual, Ray Wenderlich has a great summary and tutorial.

I found strange behaviour with AVAudioSession.

  • You can provide a category to the session, and I chose AVAudioSessionCategorySoloAmbient, which is meant to silence sound from other apps.  However it seems to also silence OpenAL and other AVAudioPlayer sounds from the same app. Switching to AVAudioSessionCategoryAmbient solved this problem for me.
  • I had set my category to AVAudioSessionCategoryAmbient while setting up the audio recorder, but changed it to AVAudioSessionCategoryRecord just before the  record command; I changed it back again after recording stops.  This worked on the simulator, but on the device the call to record simply returned NO with no explanation, and nothing was recorded.  I spent most of a day trying to work out why.  The answer: use the category AVAudioSessionCategoryPlayAndRecord while setting up the recorder.

Day 3 geolocation

My aim today was to use my new locally hosted website to test geolocation.  Again, success, thanks largely to this excellent tutorial on using geolocation in HTML5. I even have a Google map appearing showing my current location – it’s all so easy!  But, I have yet to get my head around javascript (there are clearly functions, but I am told there are no local variables, which has put me off a little). It’s making a little more sense as I dive in and just use it.


Native iPhone apps can access geolocation data in the background.  Can HTML5? Based on this stack overflow posting, I suspect not.


Phone gap on a locally hosted server

Mark and I worked together today, and the aim was to get the camera working in the app, using code on the server.

  • Putting the phone gap javascript libraries (cordova_1.6.0.js) on the server was no problem.  We created a file camera.js on the server too and included it using the <script … src=’camera.js’></script> construct. We also had to remove all javascript from the index.html file in Xcode – somehow the code on the server was calling those routines in preference to the same-named routines on the server.  The on-success routine was getting properly called at one point in the day but somehow this stopped working by the end of the day.  We also have yet to work out how to use the resulting image. Any ideas?
  • I learned that Chrome has a “javascript console” which comes in handy for debugging!  Does Safari have one?

We also decided to host a local version of the server on my Mac, to streamline testing.  It was getting a bit cumbersome to use Filezilla to transfer changes to the server code back to the server every time we wanted to test a bug.  This was pretty tricky to get working with phone gap, so here’s a summary of how we did it:

  • We downloaded MAMP (Macintosh, Apache, PHP and MySQL packaged together).
  • We then needed to transfer both the server web pages and the server database to my Mac, and then point the local copy of the web pages and the phone gap shell to the local host.
  • Go to the server’s phpMyAdmin and export the relevant database.  We found that gzipping it did not work, but zipping it did.
  • On the MAMP local host homepage (localhost:8888) there is a link to phpMyAdmin, where you can import the above file.
  • MAMP looks for the webpages at Applications/MAMP/htdocs by default.  We chose to put all our local copy of the server webpages there (though in retrospect I should probably have put them in a subdirectory), and then add a new project in Eclipse using existing files in that directory (though the workspace remains elsewhere).
  • Note that files that start with a dot, like .htaccess, do not display by default in the Finder, so when copying files around, they can get left behind. I needed to recopy .htaccess into the htdocs directory.
  • In our local webpages, we changed the mysql_connect statement to use localhost:8889, with user root and password root.  Obviously we will not put this change on the server.
  • To run this on a physical device (whether it’s a phone gap app or a regular objective-c app), we cannot refer to ‘localhost’ but the actual local IP address. We looked this up in the terminal (although it is also in the System Preferences -> Network, or you can search the Mac for Network Utilities – it is not the same as you find at and added it to the whitelist, and referred to it in the source code instead of  To complicate matters, this address has changed for me over time.

Voila!  Dinner is ready, so I must end there.


Never too late to be an indie app developer


I’ve been reading Tom Butler-Bowdon’s “Never too late to be great”, so it seems appropriate to say: today is the first day of the next 10 years. On leave from my normal work, I have devoted the day to programming – a passion of mine since 5th grade, when I used to write out code on paper to type in on my friend Russell’s computer (before my family had one).  Now I have two weeks to focus on a few projects.  I won’t say what they are yet, but they promise to be awesome.  Of course.

In the process, I got to help my son put together his 7th birthday present (a lego fire temple – lego has transformed from space to ninja since last I looked); enjoy a beautiful sunny May day; put out some washing; and pick up the kids from school.  And finish the day by setting the bread machine to have some corn bread ready in the morning.  Which is a long way of saying, I had a great first day.

This diary has its origins in some advice I received last week: inch closer to your goals every day. (Though I think it was more eloquent in its original, now forgotten, form.)  It seems pertinent to record this inching process, since otherwise it will be lost in time.

What did I achieve today?


My friend Mark and I are working on a website that will also be an app, and I’m working on “app”-ifying the existing website.  Mark’s built the site using jQuery mobile and it’s looking good in a web browser on both a desktop and an iPhone.  But we want it to be an app, with access to the phone’s phone-y capabilities.  So we have decided to use Phone Gap, which effectively provides a shell app into which you can put a whole lot of webby content (html and stuff). Loading Phone Gap 1.6 and getting the traditional “Hello World” demo going on an iPhone was not too hard (I have already used Xcode a bit).

My goals for the day were: point the app to Mark’s server so that his website suddenly looks like an app; and try to get the app to take a photo.

These goals were happily achieved.  To point the app to a server, you need to:

  • Add the server’s URL to the “white list” (e.g. in the project in Xcode, double-click on Supporting Files/Cordova.plist, and add “*” to ExternalHosts, for example).
  • Set OpenAllWhitelistURLsInWebView to YES, so that links open in the app rather than in a separate web browser.
  • In index.html, add
    <meta http-equiv=”REFRESH” content=”0; url=”>
    so that the app immediately (with a 0 second delay) shows the contents of the website.
  • I found there is always a white flash before the website displayed.  I am told using the latest versions of jQuery and jQuery Mobile should fix this; I’ll report back on this tomorrow.

Getting the app to take a photo is well described in the Apache Cordova API documentation.  The only hassle I had was I forgot to change the reference near the top of the full example from





  • My plan is to put cordova-1.6.0.js on the server and truly have a tiny shell of an app. But will this be “app”y enough for the App Store?

Mathematical web apps & visualisation