BatchingIterator
, (*1)
Small library providing an Iterator that batches requests for additional values.
This is useful as a foundation for iterators over data that is in an expensive to
access location, such as a database or a web API., (*2)
Class overview
Core interface:, (*3)
-
BatchingIterator - iterator that batches requests via a BatchingFetcher
-
BatchingFetcher - interface with fetchNext method. You will likely need to create an implementation
Utilities:, (*4)
-
MultipleBatchingFetcher - combines a number of BatchingFetcher instances into one
-
InMemoryBatchingFetcher - adapts an array to the BatchingFetcher interface
-
IteratorBasedBatchingFetcher - adapts an Iterator to the BatchingFetcher interface
Usage
Create a service that uses an Iterator., (*5)
class TweetImporter {
public function importTweets( Iterator $tweets ) {
foreach ( $tweets as $tweet ) {
$this->tweetStore->saveTweet( $tweet );
}
}
}
Note how this service only depends on Iterator. It is not aware of how the Iterator provides its
results. You thus decoupled the service from who retrieves the results, and from when this happens.
They could be coming from values already in memory, wrapped in an ArrayIterator, or be pulled from
a web service as iteration happens. Using an ArrayIterator is very helpful for testing., (*6)
Implement the BatchingFetcher interface. If you already have a service to retrieve the data, this
can be a simple wrapper., (*7)
class BatchingTweetFetcher implements BatchingFetcher {
public function fetchNext( $maxFetchCount ) {
// Make a call to some external service to fetch $tweets
return $tweets;
}
public function rewind() {
// Go back to the first tweet
}
}
Now you can easily instantiate the service, have the batching optimization, and have all
responsibilities nicely decoupled., (*8)
class TweetImportCli {
public function importTweets() {
$tweetIterator = new BatchingIterator( new BatchingTweetFetcher() );
$tweetIterator->setMaxBatchSize( 42 );
$this->tweetImporter->importTweets( $tweetIterator );
}
}
Installation
You can use Composer to download and install
this package as well as its dependencies., (*9)
To add this package as a local, per-project dependency to your project, simply add a
dependency on jeroen/batching-iterator to your project's composer.json file.
Here is a minimal example of a composer.json file that just defines a dependency on
BatchingIterator 3.x:, (*10)
{
"require": {
"jeroen/batching-iterator": "~3.0"
}
}
Release notes
Version 3.0.0 (2017-05-16)
- Dropped support for PHP 5.x
- Added scalar and return type hints
Version 2.1.2 (2014-11-02)
- The max batch size in
BatchingIterator now defaults to 10, avoiding usage of the
iterator without this value being set.
Version 2.1.1 (2014-08-19)
- Release with package name
jeroen/batching-iterator instead of jeroen-de-dauw/batching-iterator.
Version 2.1 (2014-07-19)
-
MultipleBatchingFetcher now accepts an array of BatchingFetcher in its constructor
Version 2.0 (2014-07-19)
Breaking changes:, (*11)
- Added
rewind method to the BatchingFetcher interface
- Renamed
BatchingIterator\InMemoryBatchingFetcher to BatchingIterator\Fetchers\InMemoryBatchingFetcher
New features and enhancements:, (*12)
-
BatchingIterator can now be iterated over multiple times
- Added
MultipleBatchingFetcher
- Added
IteratorBasedBatchingFetcher
Version 1.0 (2014-07-03)
Initial release with, (*13)
-
BatchingIterator class
-
BatchingFetcher interface
-
InMemoryBatchingFetcher trivial implementation of BatchingFetcher
Wallogit.com
