Harry Seldon's blog

Fractals, Chaos, and Control Systems on Rails


How to add social bookmarking features to your (Typo) blog

Posted by Harry Seldon on December 28, 2008

As you can see below I have added the social bookmarks buttons at the bottom of each article. The buttons are for the following sites.

The links will direct you to their widget page.

The code to add these buttons is:

<script src="http://digg.com/tools/diggthis.js" type="text/javascript"></script>
<a href="http://delicious.com/save" onclick="window.open('http://delicious.com/save?v=5&amp;noui&amp;jump=close&amp;url='+encodeURIComponent(location.href)+'&amp;title='+encodeURIComponent(document.title), 'delicious','toolbar=no,width=550,height=550'); return false;">
<img src="http://static.delicious.com/img/delicious.small.gif" height="50" width="50" alt="Delicious" /></a>
<script type="text/javascript" src="http://www.reddit.com/button.js?t=3"></script>
<script language="javascript" src="http://widgets.dzone.com/widgets/zoneit.js"></script> 
<a href="http://technorati.com/faves?sub=addfavbtn&amp;add=http://harryseldon.thinkosphere.com">
  <img src="http://harryseldon.thinkosphere.com/files/technorati.jpeg" alt="Add to Technorati Favorites" height="50" width="50" /></a>
<a href="javascript:location.href='http://slashdot.org/slashdot-it.pl?op=basic&amp;url='+encodeURIComponent(location.href)">
  <img src="http://harryseldon.thinkosphere.com/files/slashdot.jpeg" alt="Slashdot" border="0" height="50" width="50"></a>

Notice that the one for technorati is special. I have not found exactly what I wanted. It favorites the blog itself not only the article. Therefore, this part of the code is not suitable for your blog ! You need to adapt it. For the other links they should work as such on your blog.

If your blog engine is Typo simply add the previous code to /themes/your_theme/views/articles/read.html.erb, typically after the line :

<%= render :partial => 'article', :object => @article %>

And you which social bookmarking websites do you use ?

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Grand Gardening with GIT

Posted by Harry Seldon on November 08, 2008

Why is GIT so interesting ?

With git, I have been doing some gardening these days. Indeed I growed trees, cut branches, grafted branches.
I have been using a Version Control System (VCS) only for one year. That is about since I started the Thinkosphere project. I have been using SVN. At first I was like “Hey this is so cool”. SVN is a real time machine or at least a past time machine. You can easily go back in time to get the state of your source code from months ago. Unfortunately you cannot go forward to the future (with GIT you will be somehow able to do that !).

So after the honeymoon with svn, I began to find some limitations. Mainly I was missing an easy way to have two repositories talking to each other. Let’s see why. Here is a concrete example of how a Distributed Version Control System (DVCS) can be useful. This blog is powered by Typo which is open source. I downloaded the source code and I put it into a repository of mine to be able to make some minor changes (for instance these ones). But doing this I lost the connection with the original repo. That means I cannot easily upload my changes to the “main” repo neither can I go forward in time by downloading the last changes on the main repo.
This is exactly the kind of situation which git was designed for. Indeed with git the various repos can easily communicate with each other. So I can merge the latest updates from the main repo to my own local repo.


Let us see the setup of such a configuration in details. I will not use the example of this blog because it is still theoretical as I have not migrated it to git yet. Instead, I will use the exact configuration I am using to contribute to Open Flash Chart plugin and its test app.
Notice the setup is well explained in the excellent GIT User’s Manual at this chapter from which I am taking the following graph:

                      you push
your personal repo ------------------> your public repo
      ^                                     |
      |                                     |
      | you pull                            | they pull
      |                                     |
      |                                     |
      |               they push             V
their public repo <------------------- their repo

Let us go over the steps. Imagine you want to download OFC test app, you want to make your own modifications while being able to regularly download the updates and you also want to upload your changes.
For the configuration resulting from the following tutorial, I can precise this:

  • your personal repo = local repo = repo on your computer = repo in your working copy
  • your public repo = repo on github, mine is here
  • their repo = repo on PullMonkey’s computer
  • their public repo = ‘official’ repo = repo on PullMonkey’s github

Let me precise also some GIT Vocabulary :

  • To upload your changes from a repo to a repo is to push.
  • To download your changes to a repo from a repo is to pull (to be precise pull fetches the changes and merge them to the current branch).
  • To upload your changes from your working copy (or working tree) to your repo is to commit.
  • To download changes from your repo to your working copy is to checkout (checkout command is also a simple command to switch between branches).
  • Downloading a repo to create a repo : clone.

First, your fork the public repo to a public repo of yours: You go there you click on fork. (you will need a github account)
Then you download (clone) your repo to your local repo :

git clone git://github.com/pullmonkey/ofc_test_app.git

(It both creates the repo and checks it out)

Now you make some changes. You commit them:

git commit -a -m "my changes"

You want to upload your changes to your public repo:

git push

You want them to take into account your changes. You send them a pull request through email or github.
They agree to try it, they pull from your repo to their repo. They love it. They push it to their public repo.

They also made some more changes. You want to get them.
The first time you need to add the address of the public repo:

git remote add their_public_repo git@github.com:pullmonkey/ofc_test_app.git

Then, here is the GIT’s beauty, you pushed to a repo but you pull from another repo:

git pull their_public_repo

You can add as many repos as you want. You can see all these repos from a part of the global tree of the application development. Each repo is a tree branch. More than that each repo can contain several branches. Each branch can have a purpose: development, test, release etc. So have a happy gardening and happy time travels with git !

Any mistake, any problem or everything works ? Leave a comment !

Git resources:


As I am a private pilot, all this push/pull stuff made me think about the push/pull aircraft :

Notice it has two propellers aligned with the fuselage one to pull and one to push.

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A test and example app for Open Flash Chart Rails plugin

Posted by Harry Seldon on November 07, 2008

On October 24th, David Lowenfels aka dfl added the beginning of a test app in OFC plugin. As I had myself a local test app used to play around with OFC I thought it would be nice to add my test code in the OFC plugin. This code is actually made mainly by Charlie’s examples taken from his blog and my own examples.

A test app would be useful for 2 main reasons. The first one, as it says, is for testing purposes. The recent changes brought to OFC plugin were great but they were lacking some tests (functional tests and backward compatibility tests). So more tests are definitely necessary. The other reason which is almost more important is the need for working examples. The examples exist on Charlie’s blog and they are very helpful. As they exist why not gather them in an example app ? The examples will be yet more useful and clear.

So first, I worked directly on the app put by dfl in the test directory. But quickly I found it weird to have an application inside a plugin and using this plugin with the application inside etc. You get the kind of recursive situation (not as bad as it seems though!). So I proposed to Charlie to simply make a side test app. For now, the app is here in my repo on github but as it is more natural to put it close to the OFC plugin, Charlie will fork it and the “official” repo will be on his github repo probably here [EDIT: this is done].

[EDIT] If you also have your own OFC test app, and you want to contribute, have a look at this post explaining how to do it with GIT.

Taken from the README :
Both a testing and tutorial application for Rails Open Flash Chart Plugin.
Version 0.2.0
1) Install with:

git clone git://github.com/harryseldon/ofc_test_app.git    

EDIT PullMonkey’s version not up to date.

git clone git://github.com/pullmonkey/ofc_test_app.git    

2) Run your server:

script/server -p 3000   

3) Go to http://localhost:3000/test_it/all_graphs
You will see all the graphs, like here.

EDIT 3/9/2009 This app is running live here.

All your comments on how to test a Rails plugin are welcome.

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Scatter line chart example with OFC2

Posted by Harry Seldon on October 22, 2008

Yesterday, I needed a scatter line chart for my project. I saw that my current version of OFC did not do it. However, I saw that a new version that has the feature had come out : OFC version 2 Gamera. Looking at pullmonkey’s blog, there was nothing new so I was afraid the update was not made yet. Another look, this time directly on github and good news Charlie had updated OFC2 plugin. To be precise, last commit says “open flash chart gamera not tested yet, but available for those that want to try it out”. So let’s try out the part that interests me: the scatter line chart. I am directly translating this example from Teethgrinder just like I had done for another OFC example.

For simplicity sake, I do not use the ajax way to draw the chart. Notice also that if you adhere to the skinny controller fat model policy, the graph_code function should be in your model. Before using the following code, you need to install the edge version of OFC2 plugin (script/plugin install git://github.com/pullmonkey/open_flash_chart.git –force). Do not forget to update public/open-flash-chart.swf and public/javascripts/swfobject.js.

Then, here is the controller (test_it_controller.rb). You still have the original php code (and I still hate the $ sign before every variable).

class TestItController < ApplicationController
  def index_scatterline
    @graph = open_flash_chart_object(600,300,"/test_it/graph_code_scatterline")

  def graph_code_scatterline
    # based on this example - http://teethgrinder.co.uk/open-flash-chart-2/scatter-line-chart.php
    #$chart = new open_flash_chart();
    chart =OpenFlashChart.new
    #$title = new title( date("D M d Y") );
    title = Title.new(Date.today.to_s)
    #$chart->set_title( $title );
    #$s = new scatter_line( '#FFD600', 3 );
    scatter_line = ScatterLine.new( '#FFD600', 3 )
    #$v = array();
    v = Array.new
    #$x = 0.0;
    x = 0
    #$y = 0;
    y = 0
    while x < 25 
      #  $v[] = new scatter_value( $x, $y );
      #    // move up or down in Y axis:
      #    $y += rand(-20, 20)/10;
      y += (-1+2*rand)*2
      #    if( $y > 10 )
      #        $y = 10;
      if y>10
      #    if( $y < -10 )
      #        $y = -10;
      if y<-10
      #    $x += rand(5, 15)/10;
      x += (5+10*rand)/10
      #while( $x < 25 );
    #$s->set_values( $v );
    #$chart->add_element( $s );
    #$x = new x_axis();
    x_axis = XAxis.new
    #$x->set_range( 0, 25 );
    #$chart->set_x_axis( $x );
    chart.x_axis = x_axis
    #$y = new x_axis();
    y_axis = YAxis.new
    #$y->set_range( -10, 10 );
    y_axis.set_range( -10, 10 )
    #$chart->add_y_axis( $y );
    chart.y_axis = y_axis
    #echo $chart->toPrettyString();
    render :text => chart.to_s

The view code is as simple as usual (index_scatterline.hml.erb):

<script type="text/javascript" src="/javascripts/swfobject.js"></script>
<%= @graph %>

You can check out here the graph that is made. The graph is randomly generated so if you refresh it, it is normal that it changes. As a bonus you notice this graph looks like a stock market chart (hum is stock market random? I will need another post to explain that. Until then use your common sense).

Thanks John and thanks Charlie.

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Tutorial Rails/OFC/Ajax : Alter the chart using Javascript

Posted by Harry Seldon on September 28, 2008

In a first example I showed how to load a chart using javascript. Here I will show you how to dynamically alter an OFC chart without recreating it. This example is a raw adaptation of this Teethgrinder’s example. The chart is hard coded in ajax code so it is not loaded by OFC rails plugin, this will be done in a next example. Indeed, the aim of all this is at some point to be able to create a chart and then modify it to hide one signal or to zoom in or to change the legend, or etc.

The controller code is simple. Well OK it is even void (as I said the graph is hard coded in the javascript, it gives you opportunity to see how an OFC graph is serialized in json):

class TestItController < ApplicationController
def index_js_4

Everything happens in the view (index_js_4.html.erb) through ajax code and OFC code. I assume you have installed OFC rails plugin. You need 2 more things: the json2 library available here and the ajax code from Teethgrinder available here. Put these 2 js files in your public/javascripts folder.

The view:

        <%#= javascript_include_tag :defaults, 'swfobject' %>
        <script type="text/javascript" src="/javascripts/swfobject.js">
        <script type="text/javascript" src="/javascripts/json2.js">
        <script type="text/javascript" src="/javascripts/tutorial-js.js">
        <script type="text/javascript">

            function ofc_ready(){

            function open_flash_chart_data(){
                // alert( 'reading data' );
                return JSON.stringify(data);

            function findSWF(movieName){
                if (navigator.appName.indexOf("Microsoft") != -1) {
                    return window[movieName];
                else {
                    return document[movieName];

            var data = {
                "elements": [{
                    "type": "hbar",
                    "values": [{
                        "left": 0,
                        "right": 5
                    }, {
                        "left": 0,
                        "right": 3
                    }, {
                        "left": 4,
                        "right": 8
                    }, {
                        "left": 4,
                        "right": 8
                    }, {
                        "left": 4,
                        "right": 8
                    "colour": "#AF99DF"
                "title": {
                    "text": "Sat Sep 27 2008"
                "y_axis": {
                    "labels": ["Job 1", "Job 2", "Job 3", "Job 4", "Job 5"]
                "x_axis": {
                    "offset": false,
                    "min": 0,
                    "max": 10
        <script type="text/javascript">
            swfobject.embedSWF("/open-flash-chart.swf", "my_chart", "550", "350", "9.0.0");
    Here is the chart:
    <div id="my_chart"></div>
        <a href="javascript:update(data)">Update</a>, <a href="javascript:save(data)">Save</a>

To understand this example have a look at the js file tutorial-js.js. It contains the update and save functions. It is understandable even by someone like me who does not speak javascript fluently. You can see the live example here.

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A quick SVN tutorial

Posted by Harry Seldon on August 06, 2008

Here is a quick tuto to setup a repository with svn on an online host assuming a ssh connexion. We will use the command line as you will probably need to use it to work on your remote server.

Your local source code is in /home/localaccount/myapp

Your remote space is on /home/remoteaccount/www/

Let’s create the repository directory on your remote account :

cd /home/remoteaccount/www
mkdir svn
cd svn
mkdir myapp

Now, we tell svn to make this directory a repository:

svnadmin create –fs-type fsfs ./myapp

As a good practice, we will create the usual branches, tags, and trunk subdirectories in the repository.
First we create a directory structure :

cd /home/remoteaccount/www/
mkdir structure
cd structure
mkdir branches tags trunk

Now we import the structure:

svn import /home/remoteaccount/www/structure/. file:///home/remoteaccount/www/svn/myapp –message ‘Initial repository layout’

Finally we import the source code:
Run this command on our local account:

cd /home/localaccount/
svn import /home/localaccount/myapp/. svn+ssh://remoteaccount@ssh.mydomain.com/home/remoteaccount/www/svn/myapp/trunk –message "initial import"

(do not forget the /trunk/) If you have a ssh properly setup with rsa key you won’t have to type any password.

I find this tuto quite hostile but my point is to use the command line. In general, I use a GUI (subclipse) but the only case where I have to actually type svn commands is when I setup a repo on my remote server. Maybe you are in the same case !

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