Zend\Stdlib\Hydrator\Filter

The hydrator filters, allows you to manipulate the behavior, when you want to extract() your stuff to arrays. This is especially useful, if you want to extract() your objects to the userland and strip some internals (e.g. getServiceManager()).

It comes with a helpful Composite Implementation and a few filters for common use cases. The filters are implemented on the AbstractHydrator, so you can directly start using them if you extend it - even on custom hydrators.

namespace Zend\Stdlib\Hydrator\Filter;

interface FilterInterface
{
    /**
     * Should return true, if the given filter
     * does not match
     *
     * @param string $property The name of the property
     * @return bool
     */
    public function filter($property);
}

If it returns true, the key / value pairs will be in the extracted arrays - if it will return false, you’ll not see them again.

Filter implementations

• Zend\Stdlib\Hydrator\Filter\GetFilter

  This filter is used in the ClassMethods hydrator, to decide that getters will be extracted. It checks, if the key that should be extracted starts with get or looks like this Zend\Foo\Bar::getFoo

• Zend\Stdlib\Hydrator\Filter\HasFilter

  This filter is used in the ClassMethods hydrator, to decide that has methods will be extracted. It checks, if the key that should be extracted starts with has or looks like this Zend\Foo\Bar::hasFoo

• Zend\Stdlib\Hydrator\Filter\IsFilter

  This filter is used in the ClassMethods hydrator, to decide that is methods will be extracted. It checks, if the key that should be extracted starts with is or looks like this Zend\Foo\Bar::isFoo

• Zend\Stdlib\Hydrator\Filter\MethodMatchFilter

  This filter allows you to strip methods from the extraction with the correct condition in the composite. It checks, if the key that should be extracted matches a method name. Either getServiceLocator or Zend\Foo::getServicelocator. The name of the method is specified in the constructor of this filter. The 2nd parameter decides whether to use white or blacklisting to decide. Default is blacklisting - pass false to change it.

• Zend\Stdlib\Hydrator\Filter\NumberOfParameterFilter

  This filter is used in the ClassMethods hydrator, to check the number of parameters. By convention, the get, has and is methods do not get any parameters - but it may happen. You can add your own number of needed parameters, simply add the number to the constructor. The default value is 0

Remove filters

If you want to tell e.g. the ClassMethods hydrator, to not extract methods that start with is, you can do so:

$hydrator = new ClassMethods(false);
$hydrator->removeFilter("is");

The key / value pairs for is methods will not end up in your extracted array anymore. The filters can be used in any hydrator, but the ClassMethods hydrator is the only one, that has pre-registered filters:

$this->filterComposite->addFilter("is", new IsFilter());
$this->filterComposite->addFilter("has", new HasFilter());
$this->filterComposite->addFilter("get", new GetFilter());
$this->filterComposite->addFilter("parameter", new NumberOfParameterFilter(), FilterComposite::CONDITION_AND);

If you’re not fine with this, you can unregister them as above.

Note

The parameter for the filter on the ClassMethods looks like this by default Zend\Foo\Bar::methodName

Add filters

You can easily add filters to any hydrator, that extends the AbstractHydrator. You can use the FilterInterface or any callable:

$hydrator->addFilter("len", function($property) {
    if (strlen($property) !== 3) {
        return false;
    }
    return true;
});

By default, every filter you add will be added with a conditional or. If you want to add it with and (as the NumberOfParameterFilter that is added to the ClassMethods hydrator by default) you can do that too:

$hydrator->addFilter("len", function($property) {
    if (strlen($property) !== 3) {
        return false;
    }
    return true;
}, FilterComposite::CONDITION_AND);

Or you can add the shipped ones:

$hydrator->addFilter(
  "servicemanager",
  new MethodMatchFilter("getServiceManager"),
  FilterComposite::CONDITION_AND
);

The example above will exclude the getServiceManager method or the key from the extraction, even if the get filter wants to add it.

Use the composite for complex filters

The composite implements the FilterInterface too, so you can add it as a regular filter to the hydrator. One goody of this implementation, is that you can add the filters with a condition and you can do even more complex stuff with different composites with different conditions. You can pass the condition to the 3rd parameter, when you add a filter:

Zend\Stdlib\Hydrator\Filter\FilterComposite::CONDITION_OR

At one level of the composite, one of all filters in that condition block has to return true in order to get extracted

Zend\Stdlib\Hydrator\Filter\FilterComposite::CONDITION_AND

At one level of the composite, all of the filters in that condition block has to return true in order to get extracted

This composition will have a similar logic as the if below:

 $composite = new FilterComposite();

 $composite->addFilter("one", $condition1);
 $composite->addFilter("two", $condition2);
 $composite->addFilter("three", $condition3);
 $composite->addFilter("four", $condition4, FilterComposite::CONDITION_AND);
 $composite->addFilter("five", $condition5, FilterComposite::CONDITION_AND);

 // This is what's happening internally
 if (
      (
         $condition1
         || $condition2
         || $condition3
      ) && (
         $condition4
         && $condition5
      )
  ) {
 //do extraction
 }

If you’ve only one condition (only and or or) block, the other one will be completely ignored.

A bit more complex filter can look like this:

 $composite = new FilterComposite();
 $composite->addFilter(
     "servicemanager",
     new MethodMatchFilter("getServiceManager"),
     FilterComposite::CONDITION_AND
 );
 $composite->addFilter(
     "eventmanager",
     new MethodMatchFilter("getEventManager"),
     FilterComposite::CONDITION_AND
 );

 $hydrator->addFilter("excludes", $composite, FilterComposite::CONDITION_AND);

 // Internal
 if (
      (  // default composite inside the hydrator
         (
             $getFilter
             || $hasFilter
             || $isFilter
          ) && (
             $numberOfParameterFilter
          )
      ) && (  // new composite, added to the one above
         $serviceManagerFilter
         && $eventManagerFilter
      )
 ) {
 // do extraction
 }

If you perform this on the ClassMethods hydrator, all getters will get extracted, but not getServiceManager and getEventManager.

Using the provider interface

There is also a provider interface, that allows you to configure the behavior of the hydrator inside your objects.

 namespace Zend\Stdlib\Hydrator\Filter;

 interface FilterProviderInterface
 {
     /**
      * Provides a filter for hydration
      *
      * @return FilterInterface
      */
     public function getFilter();
 }

The getFilter() method is getting automatically excluded from extract(). If the extracted object implements the Zend\Stdlib\Hydrator\Filter\FilterProviderInterface, the returned FilterInterface instance can also be a FilterComposite.

For example:

Class Foo implements FilterProviderInterface
{
     public function getFoo()
     {
         return "foo";
     }

     public function hasFoo()
     {
         return true;
     }

     public function getServiceManager()
     {
         return "servicemanager";
     }

     public function getEventManager()
     {
         return "eventmanager";
     }

     public function getFilter()
     {
         $composite = new FilterComposite();
         $composite->addFilter("get", new GetFilter());

         $exclusionComposite = new FilterComposite();
         $exclusionComposite->addFilter(
             "servicemanager",
             new MethodMatchFilter("getServiceManager"),
             FilterComposite::CONDITION_AND
             );
         $exclusionComposite->addFilter(
             "eventmanager",
             new MethodMatchFilter("getEventManager"),
             FilterComposite::CONDITION_AND
         );

         $composite->addFilter("excludes", $exclusionComposite, FilterComposite::CONDITION_AND);

         return $composite;
     }
}

$hydrator = new ClassMethods(false);
$extractedArray = $hydrator->extract(new Foo());

The $extractedArray does only have “foo” => “foo” in. All of the others are excluded from the extraction.

Note

All pre-registered filters from the ClassMethods hydrator are ignored if this interface is used.