Too Ruby

Ruby, a programming language of which I’m quite fond, is well-known for it’s readability and ease of comprehension, among about thirty-seven other wonderful features.

I rediscovered quite how readable the language is when I genuinely ended up writing the following method last week:

# On saving, updates the #Shift counters if the #ExperienceLevel of this
# #Volunteer has been changed
def update_counters_if_experience_level_changed
  update_counters if experience_level_changed?
end

For the benefit of those of you who aren’t programmers, I’ll point out that which is obvious to those of us who are: the body of the method (that’s the line that’s indented) is almost identical to the method name (the line that starts with “def”).

This is the equivalent of going to WikiHow and looking up the article on, say, How to Make a Tie Dyed Cake, only to discover that the text of the article simply says, “Choose what colours you want, and then make a cake in those colours”… and you understand perfectly and go and make the cake, because you’ve got that good an understanding. In this metaphor, you’re the Ruby interpreter, by the way. And the cake is delicious.

Okay, I cheated a little: the experience_level_changed? method was provided for me by the Rails framework. And I had to write the update_counters method myself (although it, too, contains only one line of code in its body). But the point is still the same: writing Ruby, and thinking in a Rubyish way, produces beautifully readable, logical code.

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Kitty

~$ sudo gem install kitty
Successfully installed kitty-0.0.2
1 gem installed
Installing ri documentation for kitty-0.0.2...
Installing RDoc documentation for kitty-0.0.2...

~$ kitty
     ____
    (.   \
      \  |
       \ |___(\--/)
     __/    (  . . )
    "'._.    '-.O.'
         '-.  \ "|\
            '.,,/'.,,

~$ kitty
         /\_/\
    /\  / o o \
   //\\ \~(*)~/
   `  \/   ^ /
      | \|| ||
      \ '|| ||
       \)()-())

Kitty. That is all.

Hiding In Plain “Site”

I’ve written a program called PicInHTML, which makes web pages with concealed images which are shown when text on the page is selected. What’s clever about these page are how they work: they’re a single file, with no dependence on images nor Javascript, and they work by leveraging the little-used ::selected CSS selector. Each individual letter on the page is given a CSS class to associate it with the colour of a corresponding pixel in the source image, and selecting the text changes the background colour to that pixel colour.

That’s a wordy way of putting it. Let’s try an example:

An example of a special page - selecting the text in this page reveals the Reddit alien. Click on the image to see the discussion about this example on Reddit.

Give it a go on any of the following pages. You’ll need to not be using Microsoft Internet Explorer, I’m afraid, as it doesn’t support the ::selected CSS selector. All you have to do is select the text on the page to reveal the secret image!

If you’re interested in the mechanics of how it works, or you’d like to get a copy of the source code and have a play yourself, see my project page on PicInHTML. You could also try looking at the source code of any of the pages, above: they’re not too-hard to read, especially for machine-generated code.

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An example of a special page - selecting the text in this page reveals the Reddit alien. Click on the image to see the discussion about this example on Reddit.

T

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SSL Client Certificate Authentication In Ruby On Rails

I’ve been playing with using client-side SSL certificates (installed into your web browser) as a means to authenticate against a Ruby on Rails-powered application. This subject is geeky and of limited interest even to the people who read this blog (with the possible exception of Ruth, who may find herself doing exactly this as part of her Masters dissertation), so rather than write about it all here, I’ve written a howto/article: SSL Client Certificate Authentication In Ruby On Rails. If you’re at all interested in the topic, you’re welcome to have a read and give me any feedback.

Writing A Calendar App In Rails Vs. PHP

Some time ago, I wrote a web-based calendar application in PHP, one of my favourite programming languages. This tool would produce a HTML tabular calendar for a four week period, Monday to Sunday, in which the current date (or a user-specified date) fell in the second week (so you’re looking at this week, last week, and two weeks in the future). The user-specified date, for various reasons, would be provided as the number of seconds since the epoch (1970). In addition, the user must be able to flick forwards and backwards through the calendar, “shifting” by one or four weeks each time.

Part of this algorithm, of course, was responsible for finding the timestamp (seconds since the epoch) of the beginning of “a week last Monday”, GMT. It went something like this (pseudocode):

1. Get a handle on the beginning of "today" with [specified time] modulus [number of seconds in day]
2. Go back in time a week by deducting [number of seconds in day] multiplied by [number of days in week] (you can see I'm a real programmer, because I set "number of days in week" as a constant, in case it ever gets changed)
3. Find the previous Monday by determining what day of the week this date is on (clever functions in PHP do this for me), then take [number of seconds in day] multiplied by [number of days after Monday we are] from this to get "a week last Monday"
4. Jump forwards or backwards a number of weeks specified by the user, if necessary. Easy.
5. Of course, this isn't perfect, because this "shift backwards a week and a few days" might have put us in to "last month", in which case the calendar needs to know to deduct one month and add [number of days in last month]
6. And if we just went "back in time" beyond January, we also need to deduct a year and add 11 months. Joy.

So; not the nicest bit of code in the world.

I’ve recently been learning to program in Ruby On Rails. Ruby is a comparatively young language which has become quite popular in Japan but has only had reasonable amounts of Westernised documentation for the last four years or so. I started looking into it early this year after reading an article that compared it to Python. Rails is a web application development framework that sits on top of Ruby and promises to be “quick and structured”, becoming the “best of both worlds” between web engineering in PHP (quick and sloppy) and in Java (slow and structured). Ruby is a properly object-oriented language – even your literals are objects – and Rails takes full advantage of this.

For example, here’s my interpretation in Rails of the same bit of code as above:

@week_last_monday = 7.days.ago.gmtime.monday + params[:weeks].to_i.weeks

An explanation:

  • @week_last_monday is just a variable in which I’m keeping the result of my operation.
  • 7.days might fool you. Yes, what I’m doing there is instantiating an Integer (7, actually a Fixint, but who cares), then calling the “days” function on it, which returns me an instance of Time which represents 7 days of time.
  • Calling the ago method on my Time object, which returns me another Time object, this time one which is equal to Time.now (the time right now) minus the amount of Time I already had (7 days). Basically, I now have a handle on “7 days ago”.
  • The only thing PHP had up on me here is that it’s gmdate() function had ensured I already had my date/time in GMT; here, I have to explicitly call gmtime to do the same thing.
  • And then I simply call monday on my resulting Time object to get a handle on the beginning of the previous Monday. That simple. 24 characters of fun.
  • + params[:weeks].to_i.weeks simply increments (or decrements) the Time I have by a number of weeks specified by the user (params[:weeks] gets the number of weeks specified, to_i converts it to an integer, and weeks, like days, creates a Time object from this. In Ruby, object definitions can even override operators like +, -, <, >, etc., as if they were methods (because they are), and so the author of the Time class made it simple to perform arithmetic upon times and dates.

This was the very point at which I feel in love with Ruby on Rails.