113 lines
3.1 KiB
ReStructuredText
113 lines
3.1 KiB
ReStructuredText
Implementing ArrayAccess for Domain Objects
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===========================================
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.. sectionauthor:: Roman Borschel (roman@code-factory.org)
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This recipe will show you how to implement ArrayAccess for your
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domain objects in order to allow more uniform access, for example
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in templates. In these examples we will implement ArrayAccess on a
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`Layer Supertype <http://martinfowler.com/eaaCatalog/layerSupertype.html>`_
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for all our domain objects.
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Option 1
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--------
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In this implementation we will make use of PHPs highly dynamic
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nature to dynamically access properties of a subtype in a supertype
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at runtime. Note that this implementation has 2 main caveats:
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- It will not work with private fields
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- It will not go through any getters/setters
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.. code-block:: php
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<?php
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abstract class DomainObject implements ArrayAccess
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{
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public function offsetExists($offset) {
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return isset($this->$offset);
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}
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public function offsetSet($offset, $value) {
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$this->$offset = $value;
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}
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public function offsetGet($offset) {
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return $this->$offset;
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}
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public function offsetUnset($offset) {
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$this->$offset = null;
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}
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}
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Option 2
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--------
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In this implementation we will dynamically invoke getters/setters.
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Again we use PHPs dynamic nature to invoke methods on a subtype
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from a supertype at runtime. This implementation has the following
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caveats:
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- It relies on a naming convention
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- The semantics of offsetExists can differ
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- offsetUnset will not work with typehinted setters
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.. code-block:: php
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<?php
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abstract class DomainObject implements ArrayAccess
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{
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public function offsetExists($offset) {
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// In this example we say that exists means it is not null
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$value = $this->{"get$offset"}();
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return $value !== null;
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}
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public function offsetSet($offset, $value) {
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$this->{"set$offset"}($value);
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}
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public function offsetGet($offset) {
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return $this->{"get$offset"}();
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}
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public function offsetUnset($offset) {
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$this->{"set$offset"}(null);
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}
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}
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Read-only
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---------
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You can slightly tweak option 1 or option 2 in order to make array
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access read-only. This will also circumvent some of the caveats of
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each option. Simply make offsetSet and offsetUnset throw an
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exception (i.e. BadMethodCallException).
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.. code-block:: php
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<?php
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abstract class DomainObject implements ArrayAccess
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{
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public function offsetExists($offset) {
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// option 1 or option 2
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}
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public function offsetSet($offset, $value) {
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throw new BadMethodCallException("Array access of class " . get_class($this) . " is read-only!");
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}
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public function offsetGet($offset) {
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// option 1 or option 2
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}
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public function offsetUnset($offset) {
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throw new BadMethodCallException("Array access of class " . get_class($this) . " is read-only!");
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}
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}
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