Jtalk Smalltalk - documentation

Documentation

1. Introduction ¶

This documentation is a work in progress.

Jtalk is a young piece of code and evolves quickly. Some features are still incomplete and you may very well encounter bugs, in which case you can file an issue or a pull request on the repository.

Jtalk is an implementation of the Smalltalk-80 language. It allows developers to write client-side heavy web applications in Smalltalk. Jtalk includes an integrated development environment with a class browser, workspace and transcript.

Jtalk includes the following features:

It is semantically and syntaxically equivalent to Pharo Smalltalk (the implementation considered as the reference)
It is written in itself and compiles into efficient JavaScript
A canvas API similar to Seaside to generate HTML
A jQuery binding

2. Differences with other Smalltalk implementations ¶

3. Committing changes to disk with the web-based IDE ¶

The class browser is able to commit changes to disk. The commit category button will send a PUT request with the compiled JavaScript code of all classes in the selected class category in a file named js/CATEGORY.js.

The easiest way to enable committing is probably to setup a webdav with Apache.

The following steps explain how to setup a webdav for Jtalk with Debian, but the setup on OSX and other Linux distros should be similar.

Installing Apache and enabling the dav module

Evaluate the following as root:

~# apt-get install apache2
~# a2enmod dav
~# a2enmod dav_fs

Creating a password for the webdav

htpasswd -c /etc/apache2/htpasswd-webdav USERNAME

Setting up the webdav directory

Add the following lines to the default vhost (in /etc/apache2/sites-available/default):

Alias /jtalk/ "/path/to/jtalk/"
      <Directory "/path/to/jtalk/">
      Options Indexes MultiViews FollowSymLinks
      DirectoryIndex index.html
      AllowOverride None
      Order allow,deny
      allow from all

      Dav on

      AuthType Basic
      AuthName "jtalk"
      AuthUserFile /etc/apache2/htpasswd-webdav
      <LimitExcept GET OPTIONS>
      Require valid-user
      </LimitExcept>

      </Directory>

Make sure the group www-data has required rights to make changes to files in the webdav directory.

Restarting Apache

To restart Apache, evaluate the following:

~# /etc/init.d/apache2 restart

and go to http://localhost/jtalk/.

The class browser should now be able to commit changes to disk.

4. The counter example ¶

The following example is the traditional Seaside-like multi-counter application. The buttons at the bottom of each counter increase or decrease the counter.

Open a on the Counter class in the Canvas class category.

Each Jtalk widget is a subclass of Widget. A widget is a graphical component. The #renderOn: method is used to generate HTML using the HTML canvas.