<com:TContent ID="Main"> <h1>Creating Active Record Classes</h1> <p> We need to create two <a href="http://www.pradosoft.com/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="http://www.pradosoft.com/demos/quickstart/?page=GettingStarted.CommandLine">PRADO command line tool</a> again to generate the classes for us. </p> <p> Under the <tt>blog</tt> directory, run the following command to enter into the interactive mode of the command line tool: </p> <com:TTextHighlighter CssClass="source cli" Language="text"> php path/to/prado-cli.php shell . </com:TTextHighlighter> <p> We should see </p> <com:TTextHighlighter CssClass="source cli" Language="text"> Command line tools for Prado 3.1.0. ** Loaded PRADO appplication in directory "protected". PHP-Shell - Version 0.3.1 (c) 2006, Jan Kneschke <jan@kneschke.de> >> use '?' to open the inline help >> </com:TTextHighlighter> <p> At the prompt, enter the following two commands to create <tt>UserRecord</tt> and <tt>PostRecord</tt> classes: </p> <com:TTextHighlighter CssClass="source cli" Language="text"> >> generate users Application.database.UserRecord >> generate posts Application.database.PostRecord </com:TTextHighlighter> <p> Here we used the <a href="http://www.pradosoft.com/demos/quickstart/?page=Fundamentals.Components">namespace format</a> again to specify the classes to be created. The path <tt>Application.database.UserRecord</tt> indicates that we want the <tt>UserRecord</tt> class file to be <tt>protected/database/UserRecord.php</tt>. </p> <p> 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 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); } } </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> <p> We can use the command line tool to do some testing with our newly created Active Record classes. Still in the interactive mode of the command line tool, we enter a PHP statement and should see the following. Interested readers may try some other PHP statements, such as <tt>UserRecord::finder()->findAll()</tt>. </p> <com:TTextHighlighter CssClass="source cli" Language="text"> >> PostRecord::finder()->findAll() array ( [0] => PostRecord#1 ( [post_id] => '1' [author_id] => 'admin' [create_time] => '1175708482' [title] => 'first post' [content] => 'this is my first post' [status] => '0' [TActiveRecord:_readOnly] => false [TActiveRecord:_connection] => null [TComponent:_e] => array() ) ) </com:TTextHighlighter> <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> We can model the relationship between <tt>posts</tt> and <tt>users</tt> table in Active Record by modifying the <tt>PostRecord</tt> and <tt>UserRecord</tt> classes as follows. </p> <com:TTextHighlighter CssClass="source" Language="php"> class PostRecord extends TActiveRecord { //... properties and methods as before public $author; //holds an UserRecord public static $RELATIONS=array ( 'author' => array(self::BELONGS_TO, 'UserRecord'), ); } </com:TTextHighlighter> <p> The static <tt>$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>. The <tt>UserRecord</tt> is defined similarly below, the difference is that, the user record has many <tt>PostRecord</tt>s. </p> <com:TTextHighlighter CssClass="source" Language="php"> class UserRecord extends TActiveRecord { //... properties and methods as before public $posts=array(); //holds an array of PostRecord public static $RELATIONS=array ( 'posts' => array(self::HAS_MANY, 'PostRecord'), ); } </com:TTextHighlighter> <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.pradosoft.com/demos/quickstart/?page=Database.ActiveRecord">Active Record</a> docs. </p> </com:TContent>