I’m going to GOTO Aarhus once again

Skærmbillede 2014-06-30 kl. 22.54.08Once again – this time for the 8th year in a row – I will attend Trifork‘s excellent GOTO conference in Aarhus.

Back in 2007 when I was employed by Trifork (or “Eastfork Object Space” as they were called back then), I attended my first conference which happened to be the company’s own “JAOO” conference (which used to be GOTO’s name, even though it had not been a pure Java conference for years).

As a light green software rookie I cannot exaggerate how uplifting it was for me to start working with EOS/Trifork, and it was a profoundly inspiring experience to go to JAOO where they weren’t only talking about .NET from a Microsoft point of view – no, they would have speakers talking about open source hippie technology that weren’t even backed by any of the sponsors!

At the time Ruby was all the rage, and I distinctly remember attending Chad Fowler’s talk on Rails’ ActiveRecord which I would contrast with Hamilton Verissimo’s talk on Castle ActiveRecord, and – even though I’ve written something like 20 lines of Ruby code in my life – I’m pretty sure that I’ve come to know most of the Ruby syntax, and I’m also pretty sure that the Ruby way of doing stuff has been influencing my coding style ever since, just because I’ve been regularly and repeatedly exposed to these Ruby things.

See, this is what’s cool about going to conferences: You go to talks about wrestling DBs with Ruby, representing state with Clojure, or on how to visualize the internals of programs by doing “beautiful debugging”, and it ends up making you better at C#. You enter talks that show off visionary technologies or visionaries themselves, and then it widens your horizon. I believe the more ideas and technologies you’re exposed to, the less bound you will be to any technology in particular, which is always a good thing to strive after as a software developer.

Once again, I’m looking forward to having an injection of insight and motivation, even if it is only for two days this year instead of the usual three (I wonder what that is about?)

See you there? 🙂

Swift gesture recognizer that accepts a func

While doing iOS programming in Xamarin Studio, I’ve developed a pattern when working with gesture recognizers where I do something like this:

i.e. my gesture recognizers almost always work with a factory method that returns a recognizer whose callback closes over some local variables – this way, I have the full power of a dedicated class instance, but without the hazzle of defining a new class every time I need a new kind of recognizer.

I’ve messed around with Swift only a few days now, and I’m beginning to miss my closure-based recognizer pattern… but Swift (or, actually, the way Objective C is bridged) has a problem: When you addTarget on a gesture recognizer, it stores the callback – not as a Swift (UIGestureRecognizer) -> () reference, but rather as an Objective C selector-based target. This makes for a very un-Swifty feeling when adding the target, especially because it forces you to point to a method by typing its name in a string suffixed by “:”.

My first attempt towards supporting my beloved recognizer pattern in Swift was an extension on UIGestureRecognizer that would take a (UIGestureRecognizer) -> () as argument, wrap it in a class instance with an invoke method, and then do the addTarget call with that class instance – but then I got hit by the fact that the recognizer stores its callback targets with weak references, which means that my func-wrapping target would be gone by the time it was supposed to be used.

My current implementation seems to work fine though – I’ve extended UIPanGestureRecognizer to be able to be initialized with a (UIPanGestureRecognizer) -> () as its only argument, which it stores and has invoked by adding the invokeTarget method as the recognizer’s target.

This is the full code for the recognizer:

This way, I can use the recognizer like this:

which IMO makes for a pretty compact yet powerful way of creating focused and cohesive recognizers without a lot of boilerplate.

How to create a draggable cookie with Swift

or: “How I learned about the default value of userInteractionEnabled on UIImageViews”…

So, today I set out to create an iPad app in which my four year old son can drag some cookies around and get to do some light math.

In order to have draggable cookies, I figured the way to go would be to derive a DraggableImageView off of UIImageView that would add to itself a UIPanGestureRecognizer that would make the cookies (or any image, really) draggable.

This was my first attempt:

but for some reason I could not get it to recognize my dragging gestures! So I messed around with the code, coding various (failed) attempts at adding UIButtons and whatnot to my DraggableImageView in order to be able to do at least one single successful addTarget, but I simply could not make it work!

I loaded up some other Swift projects where my buttons worked fine, went back to the failing DraggableImageView, messed around with platform settings and other good stuff, suspecting that it was due to a bug – it is called XCode Beta, after all – and then it hit me:

  • New image view objects are configured to disregard user events by default. If you want to handle events in a custom subclass of UIImageView, you must explicitly change the value of the userInteractionEnabled property to YES after initializing the object.”
    Source: UIImageView documentation, emphasis mine.

Right! So I went and added self.userInteractionEnabled = true in the middle, which resulted in the full code reading (with nifty hover shadow effect added)

which in turn gave me these delicious draggable cookies…. Yummy!


Getting a good start with ElasticSearch

I’ve written before on how you can install ElasticSearch on a couple of Ubuntu VM’s in Azure, but while getting the database engine up and running is of course pretty important in order to start working, there are a couple of additional things that really make working with ElasticSearch super-smooth: Marvel and Kibana!

In this post I’ll show you how you can install both.


Marvel is a database monitoring tool that can show you how your ElasticSearch is feeling with a huge amount of meters and gauges – I won’t go into that here, because I haven’t actually looked at that part yet, but the thing I’m excited about is Sense, which is described as a “developer console” where you can go and do RESTful things to your ElasticSearch database.

Let’s install Marvel!

Open up a terminal and go to the root directory of your ElasticSearch installation. Depending on your platform, you’ll have to execute the following command with administrator rights, so it’s either sudo or

Skærmbillede 2014-06-13 kl. 21.11.00

for you – and then you go

which should result in downloading and installing the Marvel plugin. If it succeeds, you should be able to go to the /_plugin/marvel path of your ElasticSearch node to see all the graphs and meters I talked about. Try going to Sense by clicking on the Dashboard button in the top right corner – now you can use a lightweight cURL-like syntax with autocomplete to e.g. put a document to the database like this:


or do a quick search like this:


Neat! The Marvel plugin costs money if you want to use it for productino purposes, but as far as I can tell, it’s absolutely free to use during development, which is also the time when Sense makes the most sense, effectively meaning that you can consider Sense free.

Now, let’s check out Kibana…


Kibana is a simple generic ElasticSearch data analysis and dashboard tool that can help you visualize your data in pretty ways, and since it’s Apace V2-licensed, it’s absolutely free to use for all intents and purposes.

Since Kibana is just a modern SPA, you can go to Kibana’s GitHub and get the code which you can put in a directory or host on a web server somewhere, you’ll just need to edit the line in config.js where the ElasticSearch URL is configured.

Another option is to let ElasticSearch do the hosting, which can be easily achieved by installing Kibana as a plugin like this:

Small caveat: Installing the plugin will copy the entire source code as it looks in the Git repository, which means that the Kibana URL will become the base URL of the plugin /_plugin/kibana followed by the path /src/index.html – the full URL then becomes e.g. something like http://localhost:9200/_plugin/kibana/src/index.html.

Even though Kibana is fairly generic and can be used to visualize your ElasticSearch data in many ways, it seems to give special treatment to time series-based data, where especially logs come to mind – which is probably why it has extra-special treatment for logs imported into ElasticSearch via logstash.

That concludes this small guide on how to install Marvel and Kibana. Stay tuned for more ElasticSearch 🙂

Playing with UIView shadows in Swift

I saw a demo somewhere, where some dude created different nifty shadow effects by tweaking the shadowPath property of UIView’s CALayer. Being pretty new to Swift and iOS development, I figured it would be fun to play around with it – here’s the result (screenshot from the iPhone simulator):

four different shadow effects

Here’s how I did it – first, I installed this simple UIViewController to display the four images:

and then I created the applyPlainShadow method (which is basically the shadow example you’ll find everywhere when you Google for “UIView drop shadow”):

Simple and neat… – but now the fun begins – let’s create that convex-piece-of-paper-on-a-surface-effect that you’ll see in many places on the web – it’s created by simply using a UIBezierPath to draw the outline of the shadow, and then setting the layer’s shadowPath to the path’s CGRect:

Neat! Lastly, let’s create a blurry oval drop shadow, as if the view was hovering high over some low surface that expands into the screen… again, I’m using the shadowPath property, initializing the UIBezierPath with the overload that creates an oval shape from a rectangle: