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layout: default
title: Jtalk Smalltalk - documentation
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<div class="box last doc" id="documentation">
  <h2>Documentation</h2>
  <div class="content">

    <h3>Disclaimer</h3>

    <p class="warning">This documentation is a work in progress. If you find an error in the documentation, please <a href="https://github.com/NicolasPetton/jtalk/issues">file an issue</a>.</p>
    
    <p>This documentation <strong>doesn't aim to teach Smalltalk</strong>. Knowledge of Smalltalk is needed to understand the topics covered in this documentation. If you want to learn the Smalltalk language, you can read the excellent <a target="_blank" href="http://pharobyexamle.org">Pharo By Example</a> book.</p>


    <h3>Introduction</h3>

    <p class="information">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 <a href="https://github.com/NicolasPetton/jtalk/issues">file an issue</a> or a pull request on the <a href="https://github.com/NicolasPetton/jtalk">repository</a>.</p>

    <p>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.</p>

    <p>Jtalk includes the following features:</p>
    <ol>
      <li>It is semantically and syntaxically equivalent to <a href="http://www.pharo-project.org">Pharo Smalltalk</a> (the implementation considered as the reference)</li>
      <li>It is written in itself and compiles into efficient JavaScript</li>
      <li>A canvas API similar to <a href="http://www.seaside.st">Seaside</a> to generate HTML</li>
      <li>A <a href="http://www.jquery.com">jQuery</a> binding</li>
    </ol>

    <h3>Differences with other Smalltalk implementations</h3>

    Jtalk has some differences with other Smalltalk implementations. Because it maps Smalltalk constructs one-to-one with the JavaScript equivalent, including Smalltalk classes to JavaScript constructors, the core class library is simplified compared to Pharo Smalltalk. The following list explains the main differences:
    <ul>
      <li>There is no identity in Jtalk. Especially, there is no <code>==</code> method, or <code>Symbol</code> class. For convenience and compatibility, the Jtalk parser will recognize symbol literals as strings.</li>
      <li>The collection class hierarchy is simpler compared to most Smalltalk implementations. There is no <code>OrderedCollection</code>, <code>Set</code> or <code>SortedCollection</code>. However, the size of arrays is dynamic, and they behave like an ordered collection. They can also be sorted with the <code>#sort*</code> methods.</li>
      <li>The <code>Date</code> class behaves like the <code>Date</code> <em>and</em> <code>TimeStamp</code> classes in Pharo Smalltalk. Therefore both <code>Date today</code> and <code>Date now</code> are valid in Jtalk.</li>
      <li>Jtalk use solely <code>=</code> to test object equality and not the <code>#hash</code> method.</li>
      <li>Jtalk misses <code>thisContext</code> and does not support <code>#doesNotUnderstand</code>.</li>
    </ul>

    <h3>Committing changes to disk with the web-based IDE</h3>
    
    <p>The class browser is able to commit changes to disk. The <code>commit category</code> button will send a PUT request with the compiled JavaScript code of all classes in the selected class category in a file named <code>js/CATEGORY.js</code>.</p>
    <p>The easiest way to enable committing is probably to setup a webdav with Apache.</p>
    <p class="information">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.</p>
    <h4>Installing Apache and enabling the dav module</h4>
    <p>Evaluate the following as root:</p>
    <pre><span class="prompt">~#</span> <span class="kbd">apt-get install</span> <span class="kbd var">apache2</span>
<span class="prompt">~#</span> <span class="kbd">a2enmod</span> <span class="kbd var">dav</span>
<span class="prompt">~#</span> <span class="kbd">a2enmod</span> <span class="kbd var">dav_fs</span></pre>

    <h4>Creating a password for the webdav</h4>
    <pre><span class="prompt">~#</span> <span class="kbd">htpasswd -c /etc/apache2/htpasswd-webdav <span class="kbd var">USERNAME</span></span></pre>

    <h4>Setting up the webdav directory</h4>
    <p>Add the following lines to the default vhost (in <code>/etc/apache2/sites-available/default</code>):</p>
    <pre>Alias /jtalk/ "/path/to/jtalk/"
&lt;Directory "/path/to/jtalk/"&gt;
      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
      &lt;LimitExcept GET OPTIONS&gt;
            Require valid-user
      &lt;/LimitExcept&gt;

&lt;/Directory&gt;</pre>
    <p>Make sure the group <code>www-data</code> has required rights to make changes to files in the webdav directory.</p>
    
    <h4>Restarting Apache</h4>

    <p>To restart Apache, evaluate the following: </p>
    <pre><span class="prompt">~#</span> <span class="kbd">/etc/init.d/apache2</span> <span class="kbd var">restart</span></pre>
    <p>and go to <code>http://localhost/jtalk/</code>.</p>
    <p>The class browser should now be able to commit changes to disk.</p>

    <h3>The counter example</h3>

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

    <div id="counters"></div>
    <script type="text/javascript">
      jQuery(document).ready(function() {'#counters'._asJQuery()._append_(smalltalk.Counter._new())._append_(smalltalk.Counter._new())});
    </script>

    <p>Open a  <button onclick="smalltalk.Browser._openOn_(smalltalk.Counter);">browser</button> on the <code>Counter</code> class in the <code>Canvas</code> class category.
    <p>Each Jtalk widget is a subclass of <code>Widget</code>. A widget is a graphical component. The <code>#renderOn:</code> method is used to generate HTML using the HTML canvas.</p>

    <p class="information">Rendering methods should be placed in the <code>rendering</code> method protocol, and action methods in the <code>actions</code> protocol.</p>

    {% highlight smalltalk %}renderOn: html
    html h1 with: count asString.
    html button
    	with: '++';
    	onClick: [self increase].
    html button
    	with: '--';
    	onClick: [self decrease] {% endhighlight %}

    <h3>The HTML canvas</h3>
    <h3>Widgets</h3>
    <h3>jQuery</h3>

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