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<com:TContent ID="Main">
<h1>Creating Active Record Classes</h1>
<p>
We need to create two <a href="http://www.pradoframework.net/site/demos/quickstart/?page=Database.ActiveRecord">Active Record</a> classes, <tt>UserRecord</tt> and <tt>PostRecord</tt>, to represent data records in the <tt>users</tt> and <tt>posts</tt> tables, respectively. Active Record classes must extend from the base class <tt>ActiveRecord</tt>, and must define property names that matches with the field names of the corresponding table.
</p>
<p>
To better organize our directories, we create a new directory <tt>protected/database</tt> to hold the class files. We also modify our application configuration by inserting the following lines. It is equivalent to adding the directory <tt>protected/database</tt> to PHP include_path, which allows us to use the classes without explicitly including them.
</p>
<com:TTextHighlighter CssClass="source" Language="xml">
<paths>
<using namespace="Application.database.*" />
</paths>
</com:TTextHighlighter>
<p>
Instead of writing the classes manually, we will use the <a href="?page=GettingStarted.Wsat">PRADO Web Site Administration Tool</a> to generate the classes for us.
So we need to modify again our application configuration in the services section like follows:
</p>
<p class="block-content">
<com:TTextHighlighter CssClass="source" Language="xml">
<services>
...
<service id="wsat" class="System.Wsat.TWsatService" Password="my_secret_password" />
</services>
</com:TTextHighlighter>
</p>
<p class="block-content">
Then you are ready to go to: http://localhost/yoursite/index.php?wsat=TWsatLogin where you should see
the following page:
</p>
<img src="<%~wsat_login.png%>" style="width: 700px;" />
<p class="block-content">
In the text field you need to type the password previosly specified in the service inclusion. This
is part of a basic security system to avoid undesirable persons to use this tool.
</p>
<p class="block-content">
In order to generate AR classes you need to go to: http://localhost/divermania/index.php?wsat=TWsatGenerateAR
by clicking the proper links in the welcome page. Then you should see the following page:
</p>
<img src="<%~blog_wsat_generate_ar.png%>" style="width: 700px;" />
<p>
In the <tt>Output Folder</tt> field we used the <a href="http://www.pradoframework.net/site/demos/quickstart/?page=Fundamentals.Components">namespace format</a> again, the path <tt>Application.database</tt> indicates that we want to put our class's files in the <tt>protected/database/</tt> folder.
The <tt>*</tt> in the <tt>Table Name</tt> field means that we want to generate all AR classes, you can specify a table name instead if you want to generate just a specific AR class.
</p>
<p>
Afterward we should see the following directory structure with two new files under <tt>protected/database</tt>:
</p>
<img src="<%~ directories2.gif %>" class="output" />
<p>
If we check the <tt>PostRecord</tt> class file, we should see something similar to the following content:
</p>
<com:TTextHighlighter CssClass="source" Language="php">
class PostRecord extends TActiveRecord
{
const TABLE='posts';
public $post_id;
public $author_id;
public $create_time;
public $title;
public $content;
public $status;
public static function finder($className=__CLASS__)
{
return parent::finder($className);
}
public static $RELATIONS = array (
'author' => array(self::BELONGS_TO, 'UserRecord', 'author_id')
);
public function __toString()
{
return $this->title;
}
}
</com:TTextHighlighter>
<p>
As we see, for each field in the <tt>posts</tt> table, the class has a corresponding data member. The constant <tt>TABLE</tt> specifies the table name for the <tt>PostRecord</tt>. The static method <tt>finder()</tt> allows us to perform query and retrieve post data in terms of <tt>PostRecord</tt> objects.
</p>
<h1>Relationship Between Posts and Users</h1>
<p>
Recall that there was a foreign key relationship between the <tt>users</tt> and <tt>posts</tt> table. The entity-relationship diagram is shown below for convienence.
</p>
<img src="<%~ ER.gif %>" class="output" />
<p>
From the entity-relationship diagram above, we see that the <tt>posts</tt> table contains a field named <tt>author_id</tt>. This <tt>author_id</tt> field is a foreign key to the reference table <tt>users</tt>. In particular, the values in the <tt>author_id</tt> field should be of that from the <tt>users</tt> table's <tt>username</tt> field. One of the consequence of this relationship, thinking in terms of objects, is that each "post" belongs to an "author" and one "author" may have many "posts".
</p>
<p>
The static <tt>$RELATIONS</tt> property of <tt>PostRecord</tt> defines that the property <tt>$author</tt> belongs to an <tt>UserRecord</tt>. In <tt>array(self::BELONGS_TO, 'UserRecord')</tt>, the first element defines the relationship type, in this case <tt>self::BELONGS_TO</tt>. The second element is the name of related record, in this case an <tt>UserRecord</tt>.
</p>
<p>
An array of <tt>UserRecord</tt> with and its corresponding posts may be fetched as follows.
</p>
<com:TTextHighlighter CssClass="source" Language="php">
$users = UserRecord::finder()->withPosts()->findAll();
</com:TTextHighlighter>
<com:TipBox>
The method <tt>withXXX()</tt> (where XXX is the relationship property name, in this case, <tt>Posts</tt>) fetches the corresponding <tt>PostRecords</tt> using a second query (not by using a join). The <tt>withXXX()</tt> method accepts the same arguments as other finder methods of TActiveRecord, e.g. <tt>withPosts('status = ?', 0)</tt>.
</com:TipBox>
<p>
Further detailed documentation can be found in the quickstart <a href="http://www.pradoframework.net/site/demos/quickstart/?page=Database.ActiveRecord">Active Record</a> docs.
</p>
</com:TContent>
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