Saturday, January 2, 2010

jQuery toggle

I recently found myself in a discussion about the best way to do a toggle link. Im not saying the problem is hard, but how do you solve it nicely? Since we all hate ifs ( 2 links on why: here and here )

In jQuery there is a nice way to handle this via the toggle method. Like this:

// hide a list of related items to
}, function(){

This means if you click the link the text will be 'show' and all the list items will be hidden. The second time you click it the text will switch to 'hide' and the list items will be shown. According to the specs the toggle function could take any number of functions, which would allow you to do something crazy like:

function(){ ... },
function(){ ... },
function(){ ... },
function(){ ... }

Or why not:

function f() { ... };
function g() { ... };
function h() { ... };


But if the toggle-function is given no arguments it will toggles the visibility of the matched element. The pattern where a function behaves differently depending on the number of arguments its given is fairly typical to jQuery. For example: click() that triggers the click-event and click(function(){}) that listens for the click-event.

Friday, January 1, 2010

remember_me, passwordless login in bash.

If you find yourself having to log in to remote servers a lot, ssh-keys could be nice to use. If you don't know about ssh-keys, here is a nice introduction.

Its quite easy to set up keys following a tutorial as this. But once you have it generated, it could be quite a hassle to do all the required steps on every machine you need to access. Especially if you find your self having to access many machines, often with more than one user.

Anyways, here's a nice bash-function to set up your keys for you.

function remember_me {
ssh $1 'mkdir -p .ssh && touch .ssh/authorized_keys \
&& chmod 0700 .ssh \
&& chmod 0600 .ssh/authorized_keys \
&& cat >> .ssh/authorized_keys' <~/.ssh/
Add this to your ~/.bashrc or ~/.bash_profile file. Reload your settings using

source ~/.bashrc
or equivalent. Then just type

You will be prompted for your credentials and then. BAM! Your keys are set up.
On the subject; an other related tip is to setup your servers as aliases adding something like

alias server="ssh"
to your ~/.bashrc file.
If you set up the ssh-keys correctly you just have to type

And there you are. Now you're on the remote server.

Friday, November 16, 2007

JQuery Interface.js issues.

We use the wonderful JQuery library when developing our site. Everything works fine, and with the new 1.2.x everything is super, super fast too.

But when we upgraded to the latest version of JQuery we started to get a very strange error :
jQuery.dequeue is not a function.

After som research it turns out this is due to compability problems with the interface.js library (used for nice visual effects) and the new JQuery version. You can read about it at this thread. However the thing is that JQuery has changed it's syntax for the dequeue function from : jQuery.dequeue(elem, effect);to:jQuery(elem).dequeue(effect);So before they fix this I just added a simple patch and now everything works fine :
/* Backwards compability to make JQuery to work with interface */
$.extend({ dequeue : function(elem, effect) {

Note: doing the (xxx)(JQuery) prevents us from getting a JQuery not defined error.

Monday, September 24, 2007


I'm doing some refactoring on my spare time. Sounds horrible? Well it is. But I have some old obligations that I'm trying to finish off so I can devote all my time and energy to my new job.

My main advise for refactoring is: take one small step at the time.

For me there are mainly two cases.

1) I know the code needs refactoring but don't know how/ where to start. What I do then is that I try to locate one line of bad code or duplication and try to refactor that. And with every change I run unittests to make sure that the piece of code still works.

2) I know the code needs refactoring and I see room for improvements in every single line of the code. What I do here is still to move in small steps. Change one thing at the time and run unittests. Bad code and little unittesting always seems to be tied together, so chances are you'll end up writing a complete testsuite for the module you're refactoring. But take that extra time! Unittests are essential for refactoring, without it you'll almost never know what the effects of your changes are.

I know that when you have many ideas of code improvements it can be a pain to stop and write tests. I mean, I have an idea and then I wanna try it right away, right? This really is a problem: you have to catch all these ideas or you might forget them, but you can't act on all of them at one time. I most often solve this by writing a comment saying: FIXME and then what I want to do. This has proven to be quite useful; often when you do major refactoring you'll end up not needing some of the old code. The unneeded code is often the one that you had a nice refactoring for. I think the reason for this is that, when you're refactoring you'll see a problem that needs to be solved. You then try out every solution you can find, but sooner or later you'll eventually stick with one and this makes parts of the others obsolete.

That was about what I had to say about refactoring. ( Besides the usual advises: always strive for DRYness, encapulation, orthogonality, etc ). I'll definitely get back to this subject when I finally get to read Martin Fowlers book Refactoring.

Mocking & BDD

First of all I wanna say, if you find a bug try to catch it with a test before you fix it. When you're done, see to that the test passes. This can be hard but I think it is a great way to get better at writing tests; you'll see what you let slip the last time and then (hopfully) take it into accout the next time you implement and write tests. No, of couse it should be write tests & then implement.

I recently came across stubbing & mocking and I must say that it's great. Before I used to think that there are situations you just can't test, even if you want to. At one peticular time I was writing this file reader that needed testing, but since it used a low level C api it seemed impossible to test. Or rather, fit into our testing system. I could of course put loads of test data in our repositary, but that would really increase our testtimes. And, even more important, chances are that I then end up just testing the C api. Well you never know, you might discover some bugs but that's not really what you wanna do, is it?

For me this was a very common problem, I tried to have the tests generate the right sort of data. The problem is that these generations are complex at best and even if you manage to get it right it makes the tests hard to read as hell. Once I actually had the program I currently was developing genereate data and then manually opened it in Excel to manipulate it. Then I saved the different data with smart names like 'data_with_none_existing_article_entry.dat' and so on...

As you can imaging this is very errorprone and you'll eventually end up testing your functions against data that you don't know is right in the first place. So this is not the way to do it, so how do you do it then? The answer is that you mock.

Mocking means that you create an object. Then you tell this object to return whatever you want to have from it. Or here we have to introduce the term 'stubbing'. When you mock you expect the method you mock to be called, if it's not called exactly the number of times you specify an error will be raised. When you stub an object you just supply a couple of methods and if they happends to be called they return the specified value.

Sounds easy? Well it is. Say you developing a class that keeps track of all the grades in a school class. You're storing all the data in a database and then just do some calculations before you show it for the user. There is no need to test the database and it accessors, that belongs to another testcase possibly even to another programmer in another company. You mock the database. This can be done in a number of ways but there exists good mocking frameworks for most languages. So let me show.

def test_calc_median_grade
grades = [2, 2, 3, 3, 4, 4 , 5]
pupil = mock(' A ordinary pupil')
pupil.should_recieve(:grades).and_return( grades )
assert pupil.calc_median_grade == 3

By the way, if I do it in a more behavior driven way it would be like
describe Pupil, "grades" do

it "should have a correcly calculated median" do
grades = ....
pupil.calc_median_grade.should eql(3)


It's hard to explain why the behavior driven way is so powerful, it just is. Try it for a while and you'll see. I too was very sceptical a first.

But now back to the file reader. How do you do that? The trick is to stub /mock the 'open' function. To do this you just have to go on like I showed before but at this peticular time I was developing in python and didn't seem to find a good mocking framework for it. In the end I decided to write my own stubbed object and that's actually very easy (at least in none-typed-languages such as python). So this is what I did:
class Reader:
def open(self, foo = None):
return self
def readlines(self):
return ["foo", "bar"]
def close(self):

class SomeTestCase(testcase):
def test_module_depending_on_filereader(self):
module.Reader = Reader()
# call what ever function you wanna call
# assert what you wan't to assert.

Wednesday, September 19, 2007

A bit about security

I must admit that I don't know that much about the securing of websites. After asking around it seems that bad user input such as XSS (cross-side-scripting) are about 90% of the problem, so if you secure your website from malicious users trying to script you, you've done quite a bit about it.

I'm kind of new to XSS but now it is up to me to prevent it from happening on our site. So lets start with what XSS is. The thing is if you intend to have user input on your site and then present that input, then you are a target for scripting. (Which means that almoste every site out there are) Why? Say that you have a ordinary description field for a user. You would probably use a text area or something. Say that you just take the info from the user and then show it to him/her (I actually have a feeling that it's mostly a him), then it's totaly open for him to put every HTML-tag in the book in it, including the script-tag, and the site will render it next time it is show along with all the other HTML.

If I, for example, go <script>alert('This site sucks');</script> a ugly popup will show next time I reload the site. This could be used, and has been, for porn ads and other disturbing things you don't want on your site. But it could actually be put to use to more harmful things which I nor gonna show och know much about.

So what do you do about it? The answer is to escape it, which means that you translate all the tags into something that won't be interpretated as HTML and therefore just will be shown as text. The former example will then just show '<script>alert('This site sucks');</script>' as your presentation, which isn't that harmful.

You also have to be aware of SQL injections. which is when a user, via input, extends your queries to your database. This way they can get loads of info you don't wont to supply to a random user, such as passwords and creditcard numbers.

These problems is, as I said, very common and therefore most webframeworks have build in HTMLescaping and SQLinject prevention. So just use it. The motto is: 'Never trust user input'. Even if a users shouldn't be able to insert things in your queries or fields via your site they could do many bad things with scripts or commandline utilities such as curl.

I highly recommend that you watch this rails cast (and this and this) on this subject. And by the way, the functiion that escapes HTML for you in rails is h(). Just go : h(<script>alert('This site sucks');</script>) and your problem is solved, just don't forget to put it everywhere where malicious input/output can occur.

Tuesday, September 18, 2007

Get it real. Coding examples.

Enough theory, lets code. I guess you could prove all of your algorithms on paper. But most of the time we use an algorithm from a paper or from examples on the Internet and all you wanna do is to ensure that you've got it right.

Lets take a sorting method as an example. You wouldn't wanna invent an new algorithm for this, you probably wanna stick to quicksort or mergesort. These algorithms has already been proved so... let's go:

First write a test like:

def test_typical_sort()
array1 = [ 1, 5, 7]
array2 = [ 2, 4, 6 ]
sorted_array = sort(array2, array1)
assert sorted_array == [1, 2, 4, 5, 6, 7]

this will definitely break, I mean, we don't even have the method. So lets implement it.

def sort(array1, array2)
# insert random sort algorithm here

Now your test will work just fine. So lets test for some extremes.

def test_empty_test()
assert sort( [] , [] ) == []

And you could go on like that, you probably wanna test for some errorprone data, and so on. So when do you stop? Some say: 'test everything that could possible break'. I don't know if I agree, but it's a good thought. Some very useful hints on what to test are showed in this railscast. (Railscasts are a site with free video tutorial for rails but I think many of the stuff there is applicable for webprogramming in general. Check it out. )