May 2010


Again this week I’d been intending to work on a new client iPhone project but unfortunately it hasn’t been signed off by my client’s client, but that did leave me free to put more time into the chess app, or that was the idea (again, see last week). This week I managed two pretty solid days on the chess app and made some real progress. I’ve now got an area at the bottom of the screen showing the moves for the game and a set of buttons on the side for moving forwards and backwards in the game and for taking any alternative branches. I’ve created an internal wrapper for the game which models the game and you can send messages to it telling it to go forwards or backwards in the game, when it does this it also alerts any other objects observing it that the state has changed meaning I can automatically update the moves view and chess board view when the game is progressed.

Something I’ve spent a fair amount of time on is making sure that all the rotation code works. It can be quite fiddly making sure that when you rotate the phone all the UI components end up in the right place. The SDK does provide you with various hooks that are supposed to make things easier but in the end I’ve largely had to manually set positions of elements to make sure they go into the right places.

There’s still plenty to do on the app. To complete the elements I’ve done so far I need to add the ability to read comments that might be interspersed in the game, and to indicate better when these comments or alternative branches are available. When that’s done I really need to start working on something for managing the games that you have stored on your phone and allow downloading more, neither particularly simple jobs. I then also need to offer more functionality for reading through the game so there’s still a good way to go.

On Monday, after having my old server’s disk fill up for the umpteenth time, I decided I might as well get the server move done and dusted. I’d previously copied most of the files from my old server to my new one so all that was required was configure all the services – the web server, database server, mail server, etc. – perform another sync, copy the databases across and then switch the DNS. It actually went fairly smoothly in the end and I think I managed to keep the downtime to a minimum. The final rsync only took about 5 minutes but then the database dump and import took about 10-15 minutes each. Wasn’t helped that every time I imported the database my connection to the server seemed to hang so the import would finish (the magic of GNU Screen) but I wouldn’t actually see until I tried to do something in the window and SSH finally told me that the server had disconnected.

I don’t think I had any other real problems though and I definitely managed to get everything transferred before my app store positions script started running, so definitely within about 4 hours everything was ready. I’ve actually switched to running directly on the bare metal so I’ve gone from a virtual machine on an older server to running directly on a quite modern server. I’m glad to report that the app store positions downloads are now taking 50 minutes so basically half the time they took on the old server. Queries of the database also seem to be much faster which is really good, maybe that’ll help me to get around to writing some externally accessible query mechanisms, like a website.

The rest of the time was spent on my revision apps. On Tuesday I spent some time preparing a press release which you can find here. It’s the first press release I’ve put out about the apps and is largely intended to get a bit more attention to them just as the exam period is coming around. The apps are doing quite well and seeing increases as we get to the exam period but I’d still like to see some bigger increases to be completely happy. On Friday I prepared a few more apps for submission, it’s probably getting a bit late now but I had the material ready so seemed a shame not to use it. One was for “Human Biology” for AS-level students – another Biology app but this time focused on the human side of things. The others were for the American market. I’m actually quite excited about this, it’s a huge market and has taken relatively little effort to prepare new apps tailored to US students. The questions aren’t too different so it just required some tweaking of the grading algorithms and then repackaging. Whenever Apple get around to reviewing them we should see Grade 10 and Grade 12 Biology, Chemistry and Physics appearing in the store. Again it’s probably a bit late in the school year but it will be good to see some healthy sales in another market if this works out.

So that’s about it for the past week. Not sure what I’ll spend most time on in the next week, I do need to get version 1 of the chess app “finished” but I now have 3 other iPhone apps basically confirmed and needing completing by the end of June. Think I’ll be keeping busy for a good while yet!

Well, this past week was supposed to be devoted to a new client iPhone app. “Unfortunately” I didn’t get sign-off for it but that did mean I could keep going with my chess app. With various other bits and pieces to cover I’ve managed to spend about a day, maybe two on that in the last week. Last Monday I also ended up finishing off the wordpress blog project for Clear Digital and then taking a trip over to Manchester. I had an interesting meeting with a potential client who want to do a really big iPad project. They initially wanted me for 12 weeks full time which actually spooked me a bit as I don’t usually do full time. I’ve yet to hear what’s happening with that but could be an interesting project to work on if they do want me to go ahead with it. After that meeting I met up with Dave Verwer and went to NSManchester in the evening. While at NSManchester I gave a very hastily put together presentation on the iPhone app store positions app that I worked on the previous week. Talk seemed to go well and I had time to chat with some interesting people in the pub afterwards too.

I got home from Manchester at about 11:30 and began my planned server migration. My current server is hosted by Hetzner and is a “DS3000″, AMD Athlon 64 3700+ with 2GB memory and 2x160GB drive (probably, I bought mine over a year ago so specs may have changed). They now have an “EQ4″ which offers Intel i7-920 quadcore with 8GB memory and 2x750GB drive for exactly the same price, though with a setup fee. I’m currently hosting mapme.at on one of these and it’s running really well so I decided to upgrade my other server too. On the older server I’ve been using VMware to host most of my stuff in a virtual machine. The idea for this was that when it did come to moving servers in the future (i.e. now) I could do it by simply copying the VM across and starting it up. By about 3:30am on Tuesday morning after wrestling with VMware and networking for many hours I was getting pretty tired. I got a few hours sleep (as much as my cat would let me before she decided she needed feeding) and then tried again in the morning. After another few hours I decided that VMs were not the way to go :-/ Considering I host everything on ubuntu and that’s super easy to set up anyway the ease of setup isn’t really that big a deal, also having to copy massive virtual disk images wasn’t proving to be fun anyway. I’m going to host my services on the bare metal which means I can switch from one server to the other by doing a simple rsync to get up to date, re-syncing databases and then switching DNS. Unfortunately I haven’t yet had time to do this, ideally I’d do it overnight like I attempted last week but considering the app store positions app keeps filling up the disk and knocking out services I’m worrying less about the downtime, it should be minimal anyway now it’ll just take some resyncing.

I ended the week by attending the Liver & Mash event organised by Mandy Phillips. The event was in the spirit of previous “mashed libraries” events which have tried to introduce librarians to the concept of mashups and the many ways in which they can be useful. I wasn’t really sure what to expect from the event but had agreed to talk on “Maps” so prepared some slides and went along. In the end the event was really useful, it wasn’t really too dissimilar from other web/technology events I’ve been to. Everybody was really interested in mashups using various web APIs, hardware hacking with Arduino and other techologies, and pretty much anything that interests geeks. The libraries side of it gave it some focus but was easy to get to grips with for someone like me who has had minimal experience of libraries recently.

Most of the talks were given in three tracks and the rooms were assigned by order of popularity. As it happened my talk on maps was voted most popular and I was asked to give it in the main room to everybody! The talk seemed to be well received, looking at the twitter back channel, with most people finding the various examples I gave interesting. I only had 15 minutes so gave some basic background on maps in general and where my experience of online mapping started. I gave some examples of using mapping APIs and OpenStreetMap then finished off with a quick overview of mapme.at and my experiences of tracking my location. As usual slides can be found on slideshare (usual problems with videos, though these can be found on my user page on vimeo).

In the afternoon I also ran an hour and a half workshop on mapping. I’m not sure how well this went as we were in a fairly small room and I hadn’t particularly prepared any tasks for attendees to try out. I tried to go through some of the best ways to use mapping APIs (use mapstraction!) How to get involved with OpenStreetMap, how to edit the map using GPS, Aerial imagery or even the new Ordnance Survey data. I also covered the various ways to use OSM data including loading it into mapstraction or using the Cloudmade APIs to generate custom map styles and retrieve data through the web services. I got plenty of questions from my audience though and gave answers for all of them so hopefully they enjoyed it.

All-in-all I think the day went really well. Unfortunately when my talk finished at 3:30 I had to rush out straight away and didn’t get to enjoy the evening revelry. Instead I hopped into the car to rush to London for a leaving party!

So, a much quicker update after last week’s delayed entry. This past week I’ve been working on a project for Clear Digital. A relatively simple project that required setting up a WordPress blog and re-skinning it to match the client’s requirements. I hadn’t played with WordPress so much in quite a while so it was an interesting experience. Turned out not to be too difficult, making use of plenty of existing plugins to extend functionality. On a recommendation from Dave Coveney I used the Thematic theme. This is more of a tool than an actual theme itself. The theme you get is very simple but it allows lots of hooks to extend the theme and customise it how you like. I think there’s lots of themes that are based off this but I chose to create a new theme building on top of the very basics that Thematic provides, the better to match the client’s requirements. WordPress provides “widgets” which are small UI elements that you can drop onto the page in various places. Things like tag clouds, a calendar of your blog posts, a list of Categories, and lots of others. Thematic provides quite a few different places that you can drop Widgets making it even easier to customise your blog.

In case it helps someone else, here’s a complete list of the plugins I used:

As well as this project, I also started out on a new personal project last Sunday. I intended it to be just a quick thing to try something out but it’s started taking a lot more time and resources than I expected. As you may know I have quite a few iPhone apps in the app store. Right now I’ve got 22 live on my own account and another that I did for a client under their account. Though Apple provide perfectly good sales statistics they don’t give any indication of how well you’re doing in their “Top 100″ charts. Though much of the desire to know your position is due to vanity there are some uses to knowing, you can use it for marketing and if you reach the top 20 it’s a good reassurance that you’re going to make a reasonable sum of money from sales.

Apple don’t provide this information but a number of other people do. APPlyzer offer access to some of the data for free and require you to pay for more. An iPhone app called “PositionApp” also gives you some information and allows you to select favourite apps but still didn’t give me the information in a way that I liked, so I decided to write my own.

I had already found a perl script that would download the information for the Top 100s and would give me information for a specific app, category and country if I wanted. I was originally running this twice a day but unfortunately I hadn’t updated it to list some of my latest apps so when I found that two of my apps were in the Top 100 in the UK Education category I decided I needed a better option. If I was going to download the Top 100s I really ought to be putting them in a database them so that I could do more with them in the future.

I started by writing a script that would do the basic download of the XML and for some reason decided to throw the XML in the database for later parsing. Actually a large part of my reasoning behind this was having minimal time but wanting to leave something downloading data as I went off to OGGCamp. As it turned out storing the XML in the database was an incredibly bad idea, after a short while I had thousands of entries with 600KB of data in each meaning that an SQL query to request the latest download to check if it had changed took 15 seconds!

So, version two, parse the data straight away. The data was in XML so obviously the safest way to parse it was to use a proper XML parser. Because the file was pretty big I decided to go with a SAX style parser. After spending a while doing this and getting a completed parser going, I found that my XML parsing was taking over a minute! I’d already noticed that sometimes the HTTP request from Apple could take up 15 seconds and doing that 5000 times (for all the categories and countries) was going to take a long time, so an additional minute was terrible news!

Next day I decided to skip the “proper XML parsing” and go with a regex. After half an hour of coding I had something that would parse the entire 600KB file in less than a second, much better.

I’ve now been running this script four times a day for nearly a week. I’ve downloaded approximately 20 batches of data in that time. Each batch is pretty big as I’m querying 40 categories in 62 countries for two types of app (free and paid), which comes to 4960 requests four times a day! Each of those requests then generates 100 positions entries meaning I now have over 10 million position entries in my database. This quantity of data has been causing its own problems but so far I’m keeping on top of them. Yesterday I added a few more indexes to the tables and converted the tables from InnoDB to MyISAM. This gave much better results. The 6pm batch yesterday took 5 hours to run whereas the midnight batch took 1 hour 45 minutes and the 6am batch took just an hour to run. I’m also coincidentally hoping to move to a more powerful server this weekend so that should help too.

So, future plans for this data? Well basically I’m not sure how much effort I’m willing to put into it. The main thing that I want to get out of it is positions for all of my apps on some sort of regular basis, and the ability to query history for apps even if I haven’t specifically remembered to add them to my list. Other people might have other ideas of things to do though so I’m intending to dump the data out into some basic form, CSV most likely, and make it available to download. Hopefully I’ll get around to putting a web interface on this to allow people to look for information on their own apps or even register to get emailed position updates but any of that will be time permitting, and I’ve got lots of work to keep me busy!

If you’re interested to know though, Basic Sat Nav is continuing to do well in the UK Navigation category, hovering around the number 10 mark and hovering around the 60 mark in Ireland. My GCSE and A-Level revision apps are doing nicely in the run up to the exams, none of them getting particularly high in the Top 100 but most of them making appearances in various positions. Even iFreeThePostcode is sitting at number 60 in the UK Free Navigation category.

I’ll be talking about this project a little at NSManchester on Monday night so go along to that if you’re interested to know more.

I’m a bit worried things are getting far too samey here. This past week I spent a day fixing up a client’s buggy iPhone app and then another day working on another client’s PHP+JS property database. I also managed to get time to make some progress on an interesting client app that I’m not going to talk about in detail.


Well, that’s how I started writing this blog post a week ago, and then other activities took over and dragged me away. I attended OGGCamp over the weekend which was really interesting but did take up plenty of time. I’ll continue below and hopefully get week 93’s post out a lot sooner!

During the last week I did tweet a few times about chess moves so I’ll now admit that the interesting client iPhone app is based around chess. Obviously the rules of chess lead to some very interesting challenges while coding. For instance I had expected that validating moves was going to be very difficult to do. I think this was because I imagined taking a piece and a starting square and having to figure out all the places that it can go to. While this isn’t overly difficult it could be fiddly and time consuming.

In actuality when it came down to it I found it wasn’t so hard. In my situation I have a starting square and a destination square and need to figure out if it’s valid for a given piece. This is actually much easier, or at least was much easier for my brain to work out.

For instance with a knight, even though they have a funny way of travelling all you have to check is that they’ve travelled 2 squares sideways and 1 up or down, or vice versa, anything else is wrong. I also made sure that before doing custom moves per-piece I also did some basic sanity tests like making sure the starting square and destination were within the board and that the destination square didn’t contain a piece of the same colour.

I’ve included a screenshot above to liven this post up but it doesn’t really show what the app does, in fact the app doesn’t do very much at the moment. I’ve been very careful to keep my code very modular so I’m actually hoping to use it in a number of apps, or at least do an iPhone and iPad version of the main app. For a lot of the code I’ve even been trying to stick to pure C rather than Objective-C as I believe that will help me if I try porting this to Android.

Unfortunately I’ve had to put this app down again while working on another project this week which I’ll mention in the next post but I’m hoping to get back to the chess app again soon so that I can get it finished off and delivered to the client. I promise my next post will come a lot sooner, I’m already writing it in my head!