airportyh channel

Setting up Phusion Passenger on my slice

toby ho — Mon, 05 Jan 2009 23:47:26 -0500

As my slice is running low on memory, running multiply mongrel processes really isn't an option any more(I am too cheap to pay for more memory, in these trying economic times). Phusion passenger comes to the rescue! Phusion passenger is exactly what the rails community needed for its deployment story.

So I follow the instructions:

gem install passenger

When I did this my slice just hung indefinitely. It turns out that when gem updates the index of ruby gems, it downloads the entire index and puts it in memory, and this didn't fit in my tiny 256m I had on my slice. This thread ended up saving the day for me. I was able to do:

gem install passenger -B 1000000

it was slow but it worked.

Next up was installing the apache2 module:

passenger-install-apache2-module

First, it failed to find my apache2 installation and asked my to install it. I told it where it was by doing:

export APXS2=/usr/local/apache2/bin/apxs

Next, it didn't find the Apache Portable Runtime(APR). I told it where it was by doing:

export APR_CONFIG=/usr/local/apache2/bin/apr-1-config

Then, it didn't find the APU(whatever that is, I stopped caring). I did:

export APU_CONFIG=/usr/local/apache2/bin/apu-1-config

After all that, and running passenger-install-apache2-module again, it worked!

Next I setup the virtual host entries. I created the file /usr/local/apache2/conf/apps/tobyho.conf with these contents:

ServerName tobyho.com

DocumentRoot /var/www/apps/mywiki/public

Options FollowSymLinks

AllowOverride None

Order allow,deny

Allow from all

</Directory>

</VirtualHost>

And now I got the wiki running on mod_rails. Yea!

Things that could be as good as sex

toby ho — Sun, 04 Jan 2009 22:10:49 -0500

- peeing after it's been held a long time
- a great pooping
- having a great meal when you are really hungry
- getting lotion relieve when your hands are extremely chapped and itchy
- having running hot water over your hands when they are extremely chapped and itchy

Ruby Gotcha of the Day

toby ho — Fri, 26 Dec 2008 19:03:23 -0500

Okay, so in ruby:
>> nil or 'value'
=> "value"
because nil acts as false when used with boolean operators and any other object acts as true. Now let's assign the result to a temp variable a:
>> a = nil or 'value'
=> "value"
>> a
=> nil
Whoa?? Can you guess? In ruby the assignment operator is not special. It acts just like any other operator and does not have a lower precedence than the or operator. Therefore the expression
a = nil
executes first, which evaluates to nil, and assigns the value nil to a, and then the result nil is used in the expression nil or 'value'. Therefore to do what we intended we need to do:
>> a = (nil or 'value')
=> "value"
Wow! That is messed up.

Multiline Strings in Javascript

toby ho — Sun, 21 Dec 2008 20:32:21 -0500

I was looking through the code in facebox.js(a jQuery plugin) and I saw this:
'\
    <div id="facebox" style="display:none;"> \
      <div class="popup"> \
        <table> \
          <tbody> \
            <tr> \
              <td class="tl"/><td class="b"/><td class="tr"/> \
            </tr> \
            <tr> \
              <td class="b"/> \
              <td class="body"> \
                <div class="content"> \
                </div> \
                <div class="footer"> \
                  <a href="#" class="close"> \
                    <img src="/facebox/closelabel.gif" title="close" class="close_image" /> \
                  </a> \
                </div> \
              </td> \
              <td class="b"/> \
            </tr> \
            <tr> \
              <td class="bl"/><td class="b"/><td class="br"/> \
            </tr> \
          </tbody> \
        </table> \
      </div> \
    </div>'

Wow, I am ashamed I didn't know you could do multi-line strings like this earlier!! Although not as nice as multi-line strings in Ruby/Python/Perl, this definitely beats quotes and plus signs.

Compiler should have did-you-mean feature

toby ho — Thu, 18 Dec 2008 14:07:18 -0500

Idea: When you misspell things in your program, the compiler messages should say something like:
Error: Call to a possibly undefined method listChange, did you mean listChanged?

Developing in AIR just got a little suckier

toby ho — Thu, 18 Dec 2008 01:39:29 -0500

I wanted to try putting a javascript console inside an AIR app to aid development. I tried firebug lite, which I've been using a lot to debug IE. When I started up the app and hit F12, the console came up and everything, '1+2' gave 3, so time to rejoice? Not so fast, if you try to type 'window', or 'document', you get this error:
Error: Adobe AIR runtime security violation for JavaScript code in the application security sandbox (eval)

So they sandboxed eval and restricted access the dom and any other api that's available. And it's for... security reasons. What does Adobe have against eval? This sucks!

IE Woes: One

toby ho — Tue, 09 Dec 2008 21:09:28 -0500

Man! Have I been at war with IE lately. I have been holding back a lot of blog posts related to debug IE problems, and I going to start spewing them out now one by one. For the first installment I'll talk about one I encountered these couple of days...

Ever get this IE error?
When you click "Ok", this is what you see:

Ouch! Can this be any more catastrophic?(Yeah, that's my Chandler impression.)

According to this forum post, this happens if you have script tags in your document that's modifying other parts of the dom before the document finishes loading. Umm, okay, but I still had a hard time finding out the exact point this caused the problem. I used the comment-out-code-and-see-if-it-still-breaks-binary-search methodology, and came up with some work arounds which involved delaying the execution of some setup code. But, this catastrophic error came back to haunt be time and time again. Clearly I didn't find the root cause of this error or I wouldn't be committing it repeatedly.

But finally, I found it(I think, well at least one of the root causes). I am using firebug lite in development, which creates iframes and panels in the pages that pops out and in just like firebug. When you call console.log with firebug lite, guess what happens? Yeah, it modifies the console output window - a part of the dom that is outside of where the script tag is. Got rid of those console.log statements and fixed it.

In conclusion, do not do what I did!

IE getElementById looks up "name"

toby ho — Tue, 09 Dec 2008 16:29:00 -0500

IE, are you kidding me?

dissecting the prototype chaining

toby ho — Mon, 08 Dec 2008 14:36:17 -0500

I realized when I was trying to explain the prototype chain to my wife the other day that I didn't get it completely. So I went back to the drawing board and this is the example that I came up with:

function inherit(parent){
    var obj = function(){};
    obj.prototype = parent;
    return new obj();
}

toby = {};
toby.name = 'Toby';
toby.age = 27;
toby.eyeColor = 'brown';
toby.hairColor = 'dark';

console.log(toby);
// Object name=Toby age=27 eyeColor=brown hairColor=dark

emma = inherit(toby);
emma.name = 'Emma';
emma.age = 1

console.log(emma);
// Object name=Emma age=1 eyeColor=brown hairColor=dark

console.log("Toby is Emma's parent: " + (emma.__proto__ == toby));
// true

Windows XP tip: Hide Desktop Icons

toby ho — Sat, 06 Dec 2008 12:23:41 -0500

You can hide your desktop icons in XP by right clicking on your desktop and unchecking Arrange Icons by -> Show Desktop Icons.

Y Combinator

toby ho — Thu, 27 Nov 2008 10:29:36 -0500

This is a great article on the Y-Combinator. It talks in laymans terms. I understand now what it does and why it is useful. However, I still have no clue how the code for the Y-Combinator works.

Great Break Down Of th e Coolist Languages

toby ho — Wed, 26 Nov 2008 23:47:33 -0500

This is a great great read.