Most ruby programmers have used the next keyword in iterators like Array#each. For example…

[2, 2, 8, 4, 5, 7, 3, 8, 5, 5].each do |e|
  next if e.even?
  puts e
end

Pretty straight forward stuff here. But what you probably don’t know is that you can pass an argument to next and it would be passed back to the method that yield-ed the block. For example:

def my_method
  puts yield
end

my_method { next 'Hello World' } # => 'Hello World'

Now, I agree that this might not be the a particularly interesting example, since the last statement will automatically become the return value of yield even without the next. However, this could be very useful in some case:

class MagneticTapeReader
  def initialize
    @pointer = 0
  end

  def each_byte
    rtn = yield read(@pointer)

    if rtn.nil?
      @pointer += 1
    else
      @pointer += rtn
    end
  end
end

m = MagneticTapeReader.new

m.each_byte do |byte|
  if byte < 0x20
    next 8 # Skip ahead 8 bytes
  else
    puts byte.chr
  end
end

It’s also extremely useful when you’re writing generators of some sort. For example, if you are writing a permutation generator, it might be useful to allow the caller of your method to skip several permutations, or better yet, skip to a certain permutation.

Another note of interest is that this also works for the break keyword.

What is this project about?

In the next few weeks, we will be working on a very simple lottery program. In fact, it’s so simple that some people won’t even consider it as a computer program. Nevertheless, it covers a lot of useful concepts and sheds a light on what programming is about. Once that’s out of the way, we can build upon that knowledge and work on some really cool projects.

Will I be able to follow along?

My goal is to make this easy and fun. Anyone interested should be able to follow along, or at least that’s what I am trying to achieve. I do not expect you to have any related background. As long as you feel comfortable with following instructions like “Right Click on X and choose Y”, you should be fine!

What you will need for this project…

You will need to have a spreadsheet program installed on your computer, such as Excel from Microsoft Office, Numbers from iWork or Calc from OpenOffice.org. While the first two are commercial software, you can download OpenOffice.org for free. If you don’t feel like installing something on your computer, for the first part of the project, you should be able to follow along with Google Docs – all you need is a Google account.

If you have questions regarding how to set that up, just let me know in the comments. Otherwise I’ll see you again in about a week’s time!

First off, I just launched a new site istagable.com. It is an experimental visualization tool that helps you to generate tag clouds for any kind of data. Give it a try and let me know what you think!

Next up, I’ll finish theming this site in this winter break and (finally) start writing some tutorials. Here is a sneak peak of what it is going to look like

And finally, although I have already left OLT, I promised to update Section Widget for WordPress 2.9, so I’ll try to make some time for that as well.

Enjoy your last bits of 2009!

Of course, if you trust those who have access to your WordPress backend, the PHP shortcode plugin is always there for you. But if you are concerned about security (and you should be!), then allowing anyone to execute abitray PHP code is almost always a bad idea.

It turns out that WordPress’ shortcode API is actually very easy to use. With some minimal PHP knowlege, writing shortcodes is almost a trivial task. So, instead of allowing abitary PHP code, you can select only a few “safe” functions and turn them into shortcodes. To put this tutorial into context, let’s say we would like to display the Askimet spam counter on our frontpage. The Akismet plugin itself already provided such functionailty out of the box:

Want to show off how much spam Akismet has caught for you? Just put <?php akismet_counter(); ?> in your template.

Sweet. So how would you turn that into a shortcode? Here is all the code you’d need:

function akismet_counter_handler($atts, $content = null) {
    ob_start();

    /* Content begins - replace with your own code */
    if (function_exists('akismet_counter')){
        akismet_counter();
    }
    /* Content ends here */

    return ob_get_clean();
}

add_shortcode('akismet_counter', 'akismet_counter_handler');

Yep, that’s it. With these few lines of code you’ve created your own [akismet_counter] shortcode! Don’t worry if you have no idea what is going on here, I’m going to walk you through the details here.

Simply put, the shortcode API works very much like text subsition. To define and register a shortcode in WordPress, you need to call the add_shortcode function with two parameters – the name of the shortcode and the name of a “handler function” for this shortcode. On line 13 of the example, we are basically telling wordpress to look for any occurance of [akismet_counter] and replace that with the return value of the akismet_counter_handler PHP function.

As you might have guessed, the “handler function” is just a PHP function that returns a String. Because the akismet_counter function will directly echo its output, we created an output buffer on line 2 and returned that content as a String on line 10. Also, because our shortcode depends on another plugin which might or might not be installed or activated, it is probably a good idea to make sure the akismet_counter function actaully exists before calling it to avoid the nasty PHP error.

Now you have a brief idea of the how the shortcode API works, the only missing piece is where to put it. There are two logical places to put these kind of code – package it with your theme (inside your functions.php) or as a standalone plugin. This is ultimately a personal preference but I prefer the latter approach because it lets me keep the code in one place.

To complete this tutorial, I have packaged the sample code into a “template” which can be downloaded here. Modify it as you like and upload it to your “/wp-content/plugins/” directory, actiavte the plugin and enjoy!

(Picture by Novak Rogic)

Yep, that’s right, my Section Widget plugin has won the Grand Prize of this year’s WordPress Plugin Competition! But as you might have guessed, a lot of folks have helped me in the process of developing this plugin, and I would love to take this chance to thank all of them:

• The biggest thank you should definitely go to my boss, Novak. If he didn’t bring up this fantastic idea and generously allow me to spend my time on this, this plugin wouldn’t have existed at all! And thank you for that amazing picture
• Of course, we work as a team here at OLT, I have spent a lot of time brainstorming with my coworkers, especially Enej, Michael and Scott. They have given me lots of feekbacks and interesting ideas for improving the plugin. And I just couldn’t thank Scott enough for telling me about this competition!
• Thanks Brian Lamb and everyone else in the office for spreading the words
• Special thanks to @bachlau and Jonathan for the ReTweets!
• Thanks everyone who have helped me to test the plugin, especially those who have filed bug reports on the wordpress.org forum!
• And…. a BIG thank you to the 3712 people who have downloaded the plugin! Without you guys I would have no motivation to maintain this plugin!

Of course, I must thank all the judges for their time as well as the sponsors of the competition! I’d also encourage everyone to checkout all the other cool plugins in the competition!