Silly Ruby 1.9 trivia

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  last   # => 5

Screencasting Ruby Metaprogramming

I’ve been teaching Ruby (and in particularly, metaprogramming Ruby) for almost 7 years now. And, in that time, I’ve gradually found ways of cutting through all the confusing stuff to the actual essentials. And when you do that, suddenly things get a lot simpler. I’ve always know that Ruby didn’t really have class methods and singleton methods, for example, but until recently I didn’t have a simple way to explain that.

Then, when preparing to give an Advanced Ruby Studio, my thinking crystalized. Metaprogramming in Ruby becomes simple to explain if you focus on four things:

• Objects, not classes.


• There is only one kind of method call in Ruby. The “right-then-up” rule covers everything.


• Understanding that self can only be changed by a method call with a receiver or by a class or module definition makes it easy to keep track of what’s going on when metaprogramming.


• Knowing that Ruby keeps an internal concept of “the current class” which is where def defines its methods. Knowing what changes this makes it easier to know what’s going on.

I tried this approach in a number of Studios, and refined it during some talks for RubyFools in Copenhagen and Oslo.

So Mike Clark, who’s producing our new series of screencasts, started pushing me to put this description into video. Last week I finally cleared the decks enough to record the first three episodes.

First, I have to say it was a blast. I’d never recorded this many minutes of screencast before, and I was blown away by the amount of time it takes. I was also surprised at the level of detail involved, from microphone setup (which I messed up for a couple of segments) to color matching between codecs, it was fun to learn a whole new set of technologies.

I was also surprised at how hard it was to talk to a microphone. When we write books, we always try to write as if the reader was sitting there next to us. I tried to to the same approach with the screencasts, but it takes a whole new set of skills…

What I really liked was the way that I could live code examples to illustrate points. The first episode has maybe 50/50 code and exposition, and the second and third episodes are mostly code. And the code acts as a great skeleton on which to hang the concepts. Apple-R also keeps me honest.

So, if you’re interested in how the Ruby object model really works, and want to improve your metaprogramming chops, why not check them out?

A while back, I was asked during an interview what I’d do if I had three months off. I said I’d take piano lessons.

Well, my wife read that and very sweetly got me some. And then reality hit home. I really do have totally uncoordinated hands. I try to play, but I’m getting nowhere.

At the same time, I still enjoy noodling around with music. So my piano teacher (in a move motivated by self-preservation, no doubt) suggested we should look at composition instead. And I’ve been having a whole bunch of fun ever since.

But then Chad Fowler reminds me that the test is having it heard, which is kind of scary. But here’s my first piece. Be gentle…

(Update: people asked for the transcription: it’s here. Some of the pedal marks are screwy: I’m using Encore, and it seems to move them around every time I save. I might well end up going back to Sibelius. Forgive any amateur mistakes.)

New lambda syntax in Ruby 1.9

I’m slowly getting used to the new -> way of specifying lambdas in Ruby 1.9. I still feel that, as a notation, it could be clearer. (I’d personally like just plain backslash, because that looks pretty close to a real lambda character, but that’s not going to happen.) But having punctuation, rather than the wordlambda, makes a surprising difference to the way my eyes read code.

For example, you could write a method that acts like a while loop.

def my_while(cond, &body)
  while cond.call
    body.call
  end
end   

In Ruby 1.8  and 1.9, you could call this as

a = 0
my_while lambda { a < 5 } do
   puts a
   a += 1
end

But my brain finds that seriously hard to scan. The Ruby 1.9 -> syntax makes it slightly (just slightly, mind you) better:

a = 0
my_while  -> { a < 5 }  do
   puts a
   a += 1
end

I suspect this is just a question of time. In a year or so, we’ll parse the -> syntax in our heads without thinking twice. Once it does become natural, I suspect we’ll find all sorts of new uses for procs.

In the last week we shipped out two much anticipated books:Advanced Rails Recipes and Deploying Rails Applications: A Step-by-Step Guide. We’ve finally reached the kind of shipping volumes where we get special treatment at the Post Office—I’m now allowed to make deliveries around the back, driving my truck up to the loading dock between all the 50’ monsters. It’s an interesting insight into their business. The vast majority of stuff sitting out there during the day is the free advertising fliers that get added to your mail—pallet upon pallet of them. If we want to save the forests, finding some way of banning those things would be a start. (But, of course, they probably subsidize the mail, so doing so would double the cost of postage. In this case, that’s a price I might be willing to pay.)

Also (getting back on topic), Mike Clark has made a 12 minute video highlighting some of the more visual recipes in his book. Check out the link on the book’s home page.

Code in Presentations, Part II

OK, enough people asked, so…

http://github.com/pragdave/codex/tree/master

Every good relationship starts by establishing some basic ground rules. Here’s ours: you’re on your own. Totally, bleakly, and emptily on your own. No support. No requests for enhancements. No cards on your birthday. And I want to continue to see other developers.

But I will consider patches. In particular splitting it up so it can be installed as a Gem would be really nice. You’d probably need some kind of generator to create a new slide show. I’d guess would contain just a Rakefile, a slides/ directory and an html/ directory.

Enjoy.

Zachary has been studying karate for almost 5 years now. About 2 months ago he got cleared to test for his black belt. Since then, he’s been in intense training, leading up to two consecutive weekends of testing. Last week was the formal stuff—a verbal presentation and his kata. This weekend was the fighting part. He had to go through a set of eight self-defenses he’d created, then do some grappling. The session finished with 15 consecutive 2 minute sparring sessions with a mixture of classmates and black belts, with a 30 second break between each, topped of with a no-holds sparing session with an instructor, followed by a session of two-on-one sparring. It’s been a couple of hours, and I think all of our heart rates are all still elevated.

He has worked so incredibly hard for this. I’m so proud of him.

Now I have to work out how to live with a teenage son who is both bigger than me and formally trained in martial arts :)