Getters & Setters

Throughout ICanBoogie, magic properties are used in favor of explicit getters and setters. For instance, DateTime instances provide a minute property instead of getMinute() and setMinute() methods.

<?php

use ICanBoogie\MutableDateTime;

$time = new MutableDateTime('2013-05-17 12:30:45', 'utc');
echo $time;         // 2013-05-17T12:30:45Z
echo $time->minute; // 30
$time->minute += 120;
echo $time;         // 2013-05-17T14:30:45Z

What is a getter/setter anyway?

A getter is a method that gets the value of a specific property. On the other hand, a setter is a method that sets the value of a specific property. Getters and setters are defining with help from the AccessorTrait trait. The HasAccessor interface can be used to inform instance users of the feature.

Something to remember: Getters and setters are only invoked when their corresponding property is not accessible. This is most notably important to remember when using lazy loading, which creates the associated property when it is invoked.

Another thing to remember: You don't need to use getter/setter for everything and their cats, PHP is no Java, and it's okay to have public properties. With great power comes great responsibility. So enjoy getters/setters, but please use them wisely.

Using a combination of getters, setters, properties, and property visibilities, you can create read-only properties, write-only properties, virtual properties; but also provide a default value until a property is set, control types and guard, and lazy load values.

Read-only properties

Read-only properties are created by defining only a getter. A PropertyNotWritable exception is thrown in attempt to set a read-only property.

The following example demonstrates how a property read-only property can be implemented:

<?php

use ICanBoogie\Accessor\AccessorTrait;

/**
 * @property-read mixed $property
 */
class ReadOnlyProperty
{
    use AccessorTrait;

    protected function get_property()
    {
        return 'value';
    }
}

$a = new ReadOnlyProperty;
echo $a->property;     // value
$a->property = null;   // throws ICanBoogie\PropertyNotWritable

An existing property can be made read-only by setting its visibility to protected or private:

<?php

use ICanBoogie\Accessor\AccessorTrait;

/**
 * @property-read mixed $property
 */
class ReadOnlyProperty
{
    use AccessorTrait;

    private $property = "value";

    protected function get_property()
    {
        return $this->property;
    }
}

$a = new ReadOnlyProperty;
echo $a->property;     // value
$a->property = null;   // throws ICanBoogie\PropertyNotWritable

Protecting a construct property

Read-only properties are often used to provide read access to a property that was provided during construct, which should stay unchanged during the life time of an instance.

The following example demonstrates how a connection property passed during construct can only be read afterwards. The visibility of the property is set to private so that even an extending class cannot modify the property.

<?php

use ICanBoogie\Accessor\AccessorTrait;

class Connection
{
    …
}

/**
 * @property-read Connection $connection
 */
class Model
{
    use AccessorTrait;

    /**
     * @var Connection
     */
    private $connection;

    protected function get_connection()
    {
        return $this->connection;
    }

    protected $options;

    public function __construct(Connection $connection, array $options)
    {
        $this->connection = $connection;
        $this->options = $options;
    }
}

$connection = new Connection(…);
$model = new Model($connection, …);

$connection === $model->connection;   // true
$model->connection = null;            // throws ICanBoogie\PropertyNotWritable

Write-only properties

Write-only properties are created by defining only a setter. A PropertyNotReadable exception is thrown in attempt to get a write-only property.

The following example demonstrates how a property write-only property can be implemented:

<?php

use ICanBoogie\Accessor\AccessorTrait;

/**
 * @property-write mixed $property
 */
class WriteOnlyProperty
{
    use AccessorTrait;

    protected function set_property($value)
    {
        // …
    }
}

$a = new WriteOnlyProperty;
$a->property = 'value';
echo $a->property;   // throws ICanBoogie\PropertyNotReadable

An existing property can be made write-only by setting its visibility to protected or private:

<?php

use ICanBoogie\Accessor\AccessorTrait;

/**
 * @property-write mixed $property
 */
class WriteOnlyProperty
{
    use AccessorTrait;

    private $property = 'value';

    protected function set_property($value)
    {
        $this->property = $value;
    }
}

$a = new WriteOnlyProperty;
$a->property = 'value';
echo $a->property;   // throws ICanBoogie\PropertyNotReadable

Virtual properties

A virtual property is created by defining a getter and a setter but no corresponding property. Virtual properties are usually providing an interface to another property or data structure.

The following example demonstrates how a minutes virtual property can be implemented as an interface to a seconds property.

<?php

use ICanBoogie\Accessor\AccessorTrait;

/**
 * @property int $minutes
 */
class Time
{
    use AccessorTrait;

    public $seconds;

    protected function set_minutes($minutes)
    {
        $this->seconds = $minutes * 60;
    }

    protected function get_minutes()
    {
        return $this->seconds / 60;
    }
}

$time = new Time;
$time->seconds = 120;
echo $time->minutes;   // 2

$time->minutes = 4;
echo $time->seconds;   // 240

Provide a default value until a property is set

Because getters are invoked while their corresponding property is inaccessible, and because an unset property is of course inaccessible, it is possible to define getters providing default values until a value is actually set.

The following example demonstrates how a default value can be provided while a property is inaccessible (unset in that case). During construct, if the slug property is empty it is unset, making it inaccessible. Thus, until the property is actually set, when the slug property is read its getter is invoked and returns a default value created from the title property.

<?php

use ICanBoogie\Accessor\AccessorTrait;

class Article
{
    use AccessorTrait;

    public $title;
    public $slug;

    public function __construct($title, $slug = null)
    {
        $this->title = $tile;

        if ($slug)
        {
            $this->slug = $slug;
        }
        else
        {
            unset($this->slug);
        }
    }

    protected function get_slug()
    {
        return \ICanBoogie\normalize($this->slug);
    }
}

$article = new Article("This is my article");
echo $article->slug;   // this-is-my-article
$article->slug = "my-article";
echo $article->slug;   // my-article
unset($article->slug);
echo $article->slug;   // this-is-my-article

Façade properties (and type control)

Sometimes you want to be able to manage the type of a property, what can be stored, what can be retrieved, the most transparently possible. This can be achieved with façade properties.

Façade properties are implemented by defining a private property along with its getter and setter.

The following example demonstrates how a created_at property is implemented. It can be set to a mixed value, but is always read as a DateTime instance.

<?php

use ICanBoogie\Accessor\AccessorTrait;
use ICanBoogie\DateTime;

/**
 * @property DateTime $created_at
 */
class Article
{
    use AccessorTrait;

    private $created_at;

    protected function set_created_at($datetime)
    {
        $this->created_at = $datetime;
    }

    protected function get_created_at()
    {
        $datetime = $this->created_at;

        if ($datetime instanceof DateTime)
        {
            return $datetime;
        }

        return $this->created_at = ($datetime === null) ? DateTime::none() : new DateTime($datetime, 'utc');
    }
}

Façade properties are exported on serialization

Although façade properties are defined using private properties, they are exported when the instance is serialized, just like they would if they were public or protected.

<?php

$article = new Article;
$article->created_at = 'now';

$test = unserialize(serialize($article));
echo get_class($test->created_at);           // ICanBoogie/DateTime
$article->created_at == $test->created_at;   // true

Lazy loading

Lazy loading creates the associated property when it is invoked, making subsequent accesses using the property rather than the getter.

In the following example, the lazy_get_pseudo_uniqid() getter returns a unique value, but because the pseudo_uniqid property is created with the public visibility after the getter was called, any subsequent access to the property returns the same value:

<?php

use ICanBoogie\Accessor\AccessorTrait;

/**
 * @property string $pseudo_uniqid
 */
class PseudoUniqID
{
    use AccessorTrait;

    protected function lazy_get_pseudo_uniqid()
    {
        return uniqid();
    }
}

$a = new PseudoUniqID;

echo $a->pseudo_uniqid; // 5089497a540f8
echo $a->pseudo_uniqid; // 5089497a540f8

Of course, unsetting the created property resets the process.

<?php

unset($a->pseudo_uniqid);

echo $a->pseudo_uniqid; // 508949b5aaa00
echo $a->pseudo_uniqid; // 508949b5aaa00

Setting a lazy property

Lazy properties are implemented similarly to read-only properties, by defining a method to get a value, but unlike read-only properties lazy properties can be written too:

<?php

$a = new PseudoUniqID;

echo $a->pseudo_uniqid;   // a009b3a984a50
$a->pseudo_uniqid = 123456
echo $a->pseudo_uniqid;   // 123456

unset($a->pseudo_uniqid);
echo $a->pseudo_uniqid;   // 57e5ada092180

You need to remember that lazy properties actually create a property, thus the getter won't be invoked if the property is already accessible.

Overloading getters and setters

Because getters and setters are classic methods, they can be overloaded. That is, the setter or getter of a parent class can be overloaded by an extending class.

The following example demonstrates how an Awesome class extending an Plain class can turn a plain getter into an awesome getter:

<?php

use ICanBoogie\Accessor\AccessorTrait

/**
 * @property-read string $property
 */
class Plain
{
    use AccessorTrait;

    protected function get_property()
    {
        return "value";
    }
}

class Awesome extends
{
    protected function get_property()
    {
        return "awesome " . parent::get_property();
    }
}

$plain = new Plain;
echo $plain->property;     // value

$awesome = new Awesome;
echo $awesome->property;   // awesome value