118 lines
3.9 KiB
Markdown
118 lines
3.9 KiB
Markdown
---
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title: Access Interceptor Value Holder Proxy
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---
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# Access Interceptor Value Holder Proxy
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An access interceptor value holder is a smart reference proxy that allows you to dynamically
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define logic to be executed before or after any of the wrapped object's methods
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logic.
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It wraps around a real instance of the object to be proxied, and can be useful for things like:
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* caching execution of slow and heavy methods
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* log method calls
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* debugging
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* event triggering
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* handling of orthogonal logic, and [AOP](http://en.wikipedia.org/wiki/Aspect-oriented_programming) in general
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## Example
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Here's an example of how you can create and use an access interceptor value holder:
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```php
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<?php
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use ProxyManager\Factory\AccessInterceptorValueHolderFactory as Factory;
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require_once __DIR__ . '/vendor/autoload.php';
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class Foo
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{
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public function doFoo()
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{
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echo "Foo!\n";
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}
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}
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$factory = new Factory();
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$proxy = $factory->createProxy(
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new Foo(),
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['doFoo' => function () { echo "PreFoo!\n"; }],
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['doFoo' => function () { echo "PostFoo!\n"; }]
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);
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$proxy->doFoo();
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```
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This send something like following to your output:
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```
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PreFoo!
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Foo!
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PostFoo!
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```
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## Implementing pre- and post- access interceptors
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A proxy produced by the
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[`ProxyManager\Factory\AccessInterceptorValueHolderFactory`](https://github.com/Ocramius/ProxyManager/blob/master/src/ProxyManager/Factory/AccessInterceptorValueHolderFactory.php)
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implements the
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[`ProxyManager\Proxy\AccessInterceptorValueHolderInterface`](https://github.com/Ocramius/ProxyManager/blob/master/src/ProxyManager/Proxy/AccessInterceptorValueHolderInterface.php).
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Therefore, you can set an access interceptor callback by calling:
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```php
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$proxy->setMethodPrefixInterceptor('methodName', function () { echo 'pre'; });
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$proxy->setMethodSuffixInterceptor('methodName', function () { echo 'post'; });
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```
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You can also listen to public properties access by attaching interceptors to `__get`, `__set`, `__isset` and `__unset`.
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A prefix interceptor (executed before method logic) should have the following signature:
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```php
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/**
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* @var object $proxy the proxy that intercepted the method call
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* @var object $instance the wrapped instance within the proxy
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* @var string $method name of the called method
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* @var array $params sorted array of parameters passed to the intercepted
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* method, indexed by parameter name
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* @var bool $returnEarly flag to tell the interceptor proxy to return early, returning
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* the interceptor's return value instead of executing the method logic
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*
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* @return mixed
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*/
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$prefixInterceptor = function ($proxy, $instance, $method, $params, & $returnEarly) {};
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```
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A suffix interceptor (executed after method logic) should have the following signature:
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```php
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/**
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* @var object $proxy the proxy that intercepted the method call
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* @var object $instance the wrapped instance within the proxy
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* @var string $method name of the called method
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* @var array $params sorted array of parameters passed to the intercepted
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* method, indexed by parameter name
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* @var mixed $returnValue the return value of the intercepted method
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* @var bool $returnEarly flag to tell the proxy to return early, returning the interceptor's
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* return value instead of the value produced by the method
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*
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* @return mixed
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*/
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$suffixInterceptor = function ($proxy, $instance, $method, $params, $returnValue, & $returnEarly) {};
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```
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## Known limitations
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* methods using `func_get_args()`, `func_get_arg()` and `func_num_arg()` will not function properly
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for parameters that are not part of the proxied object interface: use
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[variadic arguments](http://php.net/manual/en/functions.arguments.php#functions.variable-arg-list)
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instead.
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## Tuning performance for production
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See [Tuning ProxyManager for Production](https://github.com/Ocramius/ProxyManager/blob/master/docs/tuning-for-production.md).
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