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access-interceptor-scope-localizer.md
001 # Access Interceptor Scope Localizer Proxy
002
003 An access interceptor scope localizer is a smart reference proxy that allows you to dynamically
004 define logic to be executed before or after any of the proxied object's methods' logic.
005
006 It works exactly like the [access interceptor value holder](access-interceptor-value-holder.md),
007 with some minor differences in behavior.
008
009 The working concept of an access interceptor scope localizer is to localize scope of a proxied object:
010
011 ```php
012 class Example
013 {
014 protected $foo;
015 protected $bar;
016 protected $baz;
017
018 public function doFoo()
019 {
020 // ...
021 }
022 }
023
024 class ExampleProxy extends Example
025 {
026 public function __construct(Example $example)
027 {
028 $this->foo = & $example->foo;
029 $this->bar = & $example->bar;
030 $this->baz = & $example->baz;
031 }
032
033 public function doFoo()
034 {
035 return parent::doFoo();
036 }
037 }
038 ```
039
040 This allows to create a mirror copy of the real instance, where any change in the proxy or in the real
041 instance is reflected in both objects.
042
043 The main advantage of this approach is that the proxy is now safe against fluent interfaces, which
044 would break an [access interceptor value holder](access-interceptor-value-holder.md) instead.
045
046 ## Differences with [access interceptor value holder](access-interceptor-value-holder.md):
047
048 * It does **NOT** implement the `ProxyManager\Proxy\ValueHolderInterface`, since the proxy itself
049 does not keep a reference to the original object being proxied
050 * In all interceptor methods (see [access interceptor value holder](access-interceptor-value-holder.md)),
051 the `$instance` passed in is the proxy itself. There is no way to gather a reference to the
052 original object right now, and that's mainly to protect from misuse.
053
054 ## Known limitations
055
056 * It is **NOT** possible to intercept access to public properties
057 * It is **NOT** possible to proxy interfaces, since this proxy relies on `parent::method()` calls.
058 Interfaces obviously don't provide a parent method implementation.
059 * calling `unset` on a property of an access interceptor scope localizer (or the real instance)
060 will cause the two objects to be un-synchronized, with possible unexpected behaviour.
061 * serializing or un-serializing an access interceptor scope localizer (or the real instance)
062 will not cause the real instance (or the proxy) to be serialized or un-serialized
063 * if a proxied object contains private properties, then an exception will be thrown if you use
064 PHP `< 5.4.0`.
065
066 ## Example
067
068 Here's an example of how you can create and use an access interceptor scope localizer :
069
070 ```php
071 <?php
072
073 use ProxyManager\Factory\AccessInterceptorScopeLocalizerFactory as Factory;
074
075 require_once __DIR__ . '/vendor/autoload.php';
076
077 class Foo
078 {
079 public function doFoo()
080 {
081 echo "Foo!\n";
082 }
083 }
084
085 $factory = new Factory();
086
087 $proxy = $factory->createProxy(
088 new Foo(),
089 array('doFoo' => function () { echo "PreFoo!\n"; }),
090 array('doFoo' => function () { echo "PostFoo!\n"; })
091 );
092
093 $proxy->doFoo();
094 ```
095
096 This send something like following to your output:
097
098 ```
099 PreFoo!
100 Foo!
101 PostFoo!
102 ```
103
104 This is pretty much the same logic that you can find
105 in [access interceptor value holder](access-interceptor-value-holder.md).
106