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Behaviors

Behaviors are a great way to package model extensions for reusability. They are powerful, versatile, fast, and help you organize your code in a better way.

Pre and Post Hooks For save() And delete() Methods

The save() and delete() methods of your generated objects are easy to override. In fact, Propel looks for one of the following methods in your objects and executes them when needed:

  • preInsert: code executed before insertion of a new object
  • postInsert: code executed after insertion of a new object
  • preUpdate: code executed before update of an existing object
  • postUpdate: code executed after update of an existing object
  • preSave: code executed before saving an object (new or existing)
  • postSave: code executed after saving an object (new or existing)
  • preDelete: code executed before deleting an object
  • postDelete: code executed after deleting an object

For example, you may want to keep track of the creation date of every row in the book table. In order to achieve this behavior, you can add a created_at column to the table in schema.xml:

<table name="book">
  ...
  <column name="created_at" type="timestamp" />
</table>

Then, you can force the update of the created_at column before every insertion as follows:

<?php
class Book extends BaseBook
{
  public function preInsert(ConnectionInterface $con = null)
  {
    $this->setCreatedAt(time());
    return true;
  }
}

Whenever you call save() on a new object, Propel now executes the preInsert() method on this objects and therefore update the created_at column:

<?php
$b = new Book();
$b->setTitle('War And Peace');
$b->save();
echo $b->getCreatedAt(); // 2009-10-02 18:14:23

Warning: If you implement preInsert(), preUpdate(), preSave() or preDelete(), these methods must return a boolean value. Any return value other than true stops the action (save or delete). This is a neat way to bypass persistence on some cases, but can also create unexpected problems if you forget to return true.

Tip
Since this feature adds a small overhead to write operations, you can disable it completely in your build properties by setting propel.addHooks to false.

# -------------------
#  TEMPLATE VARIABLES
# -------------------
propel.addHooks = false

Introducing Behaviors

When several of your custom model classes end up with similar methods added, it is time to refactor the common code.

For example, you may want to add the same ability you gave to Book to all the other objects in your model. Let's call this the "Timestampable behavior", because then all of your rows have a timestamp marking their creation. In order to achieve this behavior, you have to repeat the same operations on every table. First, add a created_at column to the other tables:

<table name="book">
  ...
  <column name="created_at" type="timestamp" />
</table>
<table name="author">
  ...
  <column name="created_at" type="timestamp" />
</table>

Then, add a preInsert() hook to the object stub classes:

<?php
class Book extends BaseBook
{
  public function preInsert()
  {
    $this->setCreatedAt(time());
    return true;
  }
}

class Author extends BaseAuthor
{
  public function preInsert()
  {
    $this->setCreatedAt(time());
    return true;
  }
}

Even if the code of this example is very simple, the repetition of code is already too much. Just imagine a more complex behavior, and you will understand that using the copy-and-paste technique soon leads to a maintenance nightmare.

Propel offers three ways to achieve the refactoring of the common behavior. The first one is to use a custom builder during the build process. This can work if all of your models share one single behavior. The second way is to use table inheritance. The inherited methods then offer limited capabilities. And the third way is to use Propel behaviors. This is the right way to refactor common model logic.

Behaviors are special objects that use events called during the build process to enhance the generated model classes. Behaviors can add attributes and methods to both the tableMap and model classes, they can modify the course of some of the generated methods, and they can even modify the structure of a database by adding columns or tables.

For instance, Propel bundles a behavior called timestampable, which does exactly the same thing as described above. But instead of adding columns and methods by hand, all you have to do is to declare it in a <behavior> tag in your schema.xml, as follows:

<table name="book">
  ...
  <behavior name="timestampable" />
</table>
<table name="author">
  ...
  <behavior name="timestampable" />
</table>

Then rebuild your model, and there you go: two columns, created_at and updated_at, were automatically added to both the book and author tables. Besides, the generated BaseBook and BaseAuthor classes already contain the code necessary to auto-set the current time on creation and on insertion.

Bundled Behaviors

Propel currently bundles several behaviors. Check the behavior documentation for details on usage:

You can also look at user contributed behaviors.

Behaviors bundled with Propel require no further installation and work out of the box.

Customizing Behaviors

Behaviors often offer some parameters to tweak their effect. For instance, the timestampable behavior allows you to customize the names of the columns added to store the creation date and the update date. The behavior customization occurs in the schema.xml, inside <parameter> tags nested in the <behavior> tag. So let's set the behavior to use created_on instead of created_at for the creation date column name (and same for the update date column):

<table name="book">
  ...
  <behavior name="timestampable">
    <parameter name="create_column" value="created_on" />
    <parameter name="update_column" value="updated_on" />
  </behavior>
</table>

If the columns already exist in your schema, a behavior is smart enough not to add them one more time.

<table name="book">
  ...
  <column name="created_on" type="timestamp" />
  <column name="updated_on" type="timestamp" />
  <behavior name="timestampable">
    <parameter name="create_column" value="created_on" />
    <parameter name="update_column" value="updated_on" />
  </behavior>
</table>

Using Third-Party Behaviors

As a Propel behavior can be packaged into a single class, behaviors are quite easy to reuse and distribute across several projects. All you need to do is to copy the behavior file into your project, and declare it in build.properties, as follows:

# ----------------------------------
#  B E H A V I O R   S E T T I N G S
# ----------------------------------

propel.behavior.timestampable.class = propel.engine.behavior.timestampable.TimestampableBehavior
# Add your custom behavior paths here
propel.behavior.formidable.class = path.to.FormidableBehavior

Propel will then find the FormidableBehavior class whenever you use the formidable behavior in your schema:

<table name="author">
  ...
  <behavior name="timestampable" />
  <behavior name="formidable" />
</table>

Tip
If you use autoloading during the build process, and if the behavior classes benefit from the autoloading, then you don't even need to declare the path to the behavior class.

Applying a Behavior To All Tables

You can add a <behavior> tag directly under the <database> tag. That way, the behavior will be applied to all the tables of the database.

<database name="propel">
  <behavior name="timestampable" />
  <table name="book">
    ...
  </table>
  <table name="author">
    ...
  </table>
</database>

In this example, both the book and author table benefit from the timestampable behavior, and therefore automatically update their created_at and updated_at columns upon saving.

Going one step further, you can even apply a behavior to all the databases of your project, provided the behavior doesn't need parameters - or can use default parameters. To add a behavior to all databases, simply declare it in the project's build.properties under the propel.behavior.default key, as follows:

propel.behavior.default = archivable, timestampable

Writing a Behavior

Check the behaviors bundled with Propel to see how to implement your own behavior: they are the best starting point to understanding the power of behaviors and builders.

Modifying the Data Model

Behaviors can modify their table, and even add another table, by implementing the modifyTable method. In this method, use $this->getTable() to retrieve the table buildtime model and manipulate it.

For instance, to add a new column named 'foo' in the current table, add the following method to a behavior:

<?php
class MyBehavior extends Behavior
{
  // default parameters value
  protected $parameters = array(
    'column_name' => 'foo',
  );

  public function modifyTable()
  {
    $table = $this->getTable();
    $columnName = $this->getParameter('column_name');
    // add the column if not present
    if(!$this->getTable()->hasColumn($columnName)) {
      $column = $this->getTable()->addColumn(array(
        'name'    => $columnName,
        'type'    => 'INTEGER',
      ));
    }
  }
}

Modifying the ActiveRecord Classes

Behaviors can add code to the generated model object by implementing one of the following methods:

  • objectAttributes: add attributes to the object
  • objectMethods: add methods to the object
  • preInsert: add code to be executed before insertion of a new object
  • postInsert: add code to be executed after insertion of a new object
  • preUpdate: add code to be executed before update of an existing object
  • postUpdate: add code to be executed after update of an existing object
  • preSave: add code to be executed before saving an object (new or existing)
  • postSave: add code to be executed after saving an object (new or existing)
  • preDelete: add code to be executed before deleting an object
  • postDelete: add code to be executed after deleting an object
  • objectCall: add code to be executed inside the object's __call()
  • objectFilter($script): do whatever you want with the generated code, passed as reference

Modifying the Query Classes

Behaviors can also add code to the generated query objects by implementing one of the following methods:

  • queryAttributes: add attributes to the query class
  • queryMethods: add methods to the query class
  • preSelectQuery: add code to be executed before selection of a existing objects
  • preUpdateQuery: add code to be executed before update of a existing objects
  • postUpdateQuery: add code to be executed after update of a existing objects
  • preDeleteQuery: add code to be executed before deletion of a existing objects
  • postDeleteQuery: add code to be executed after deletion of a existing objects
  • queryFilter(&$script): do whatever you want with the generated code, passed as reference

Modifying the TableMap Classes

Behaviors can also add code to the generated TableMap objects by implementing one of the following methods:

  • staticAttributes: add static attributes to the TableMap class
  • staticMethods: add static methods to the TableMap class
  • tableMapFilter(&$script): do whatever you want with the generated code, passed as reference

Adding New Classes

Behaviors can add entirely new classes based on the data model. To build a new class, a behavior must provide an array of builder class names (in return to getAdditionalBuilders()) and the builder classes themselves.

For instance, to add an empty child class for the ActiveRecord class, create the following behavior:

<?php
require_once 'AddChildBehaviorBuilder.php';

class AddChildBehavior extends Behavior
{
    protected $additionalBuilders = array('AddChildBehaviorBuilder');
}

Next, write a builder extending the OMBuilder class, and implement the getUnprefixedClassName(), addClassOpen(), and addClassBody() methods:

<?php
class AddChildBehaviorBuilder extends OMBuilder
{

    public function getUnprefixedClassname()
    {
        return $this->getStubObjectBuilder()->getUnprefixedClassname() . 'Child';
    }

    protected function addClassOpen(&$script)
    {
        $table = $this->getTable();
        $tableName = $table->getName();
        $script .= "
/**
 * Test class for Additional builder enabled on the '$tableName' table.
 *
 */
class " . $this->getClassname() . " extends " . $this->getStubObjectBuilder() . "
{
";
    }

    protected function addClassBody(&$script)
    {
        $script .= "  // no code";
    }

    protected function addClassClose(&$script)
    {
        $script .= "
}";
    }
}

By default, classes added by a behavior are generated each time the model is rebuilt. To limit the generation to the first time (for instance for stub classes), add a public $overwrite attribute to the builder and set it to false.

You can set the additional class to be generated in a subfolder by implementing the getPackage() method.

Replacing or Removing Existing Methods

Behaviors can modify existing methods even if no hook is called in the builders, thanks to a service class called PropelPHPParser. This class can remove a method, replace a method by another one, or add a new method before or after an existing one.

The PropelPHPParser constructor takes a string as input, so it is best used inside "filter" hooks in behaviors. For instance, to replace the findPk() method in the generated query class by a custom one, use the following syntax:

<?php
class FastPkFindBehavior extends Behavior
{
    public function queryFilter(&$script)
    {
      $newFindPkMethod = "
public function findPk(\$key, \$con = null)
{
  \$query = 'SELECT * from `%s` WHERE id = ?';
  if (null === \$con) {
    \$con = Propel::getReadConnection(%sTableMap::DATABASE_NAME);
  }
  \$stmt = \$con->prepare(\$query);
  \$stmt->bindValue(1, \$key);
  \$res = \$stmt->execute();
  // hydrate ActiveRecord objects with the result
  \$formatter = new \Propel\Runtime\Formatter\ObjectFormatter();
  \$formatter->setClass('%s');
  return \$formatter->formatOne(\$con->getSingleDataFetcher($stmt));
}
";
    $table = $this->getTable();
    $newFindPkMethod = sprintf($newFindPkMethod, $table->getName(), $table->getPhpName(), $table->getPhpName());
    $parser = new PropelPHPParser($script, true);
    $parser->replaceMethod('findPk', $newFindPkMethod);
    $script = $parser->getCode();
  }
}

The PropelPHPParser class provides the following utility methods:

  • removeMethod($methodName)
  • replaceMethod($methodName, $newCode)
  • addMethodAfter($methodName, $newCode)
  • addMethodBefore($methodName, $newCode)

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