writers.md

Plum is a data processing pipeline that helps you to write structured, reusable and well tested data processing code.

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Index Workflow Readers Writers Filters Converters Extensions

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Use writers to write the result of the workflow. The target doesn't necessarily have to write to a persistent storage, you can also write, for example, into arrays or objects. Writers must implement the WriterInterface that provides three methods: writeItem(), prepare() and finish(). The workflow calls prepare() before it reads the first item and finish() after it read the last item.

Multiple writers can be added to a workflow in any ordering. Therefore it is possible to filter the read items, write them somewhere, further filter them and then write them elsewhere.

Table of Contents

• Adding Writers
• Conditional Writers
• Default Writers
• Custom Writers

Adding Writers

Writer can be added to a workflow by calling addWriter() with an instance of Plum\Plum\Writer\WriterInterface.

use Plum\Plum\Writer\ArrayWriter;

$workflow = new Workflow();
$workflow->addWriter(['writer' => new ArrayWriter()]);

You can also directly pass the writer to addWriter() if you don't want to set any other options.

use Plum\Plum\Writer\ArrayWriter;

$workflow = new Workflow();
$workflow->addWriter(new ArrayWriter());

By default writers are appended at the end of the workflow. You can use the position option to change the default behaviour.

use Plum\Plum\Writer\ArrayWriter;

$workflow = new Workflow();
$workflow->addWriter([
    'writer'   => new ArrayWriter(),
    'position' => Workflow::PREPEND
]);

Conditional Writers

Very much like Conditional Converters writers can be conditional and an item will only be written if a filter returns true for the given item. Filters can be an instance of Plum\Plum\Filter\FilterInterface or a function.

$workflow->addWriter([
    'writer' => $writer,
    'filter' => $filter,
]);

Unlike converters, writers currently do not support the filterField option.

Conditional writers can be used to split data from one source and write it to different targets. For example,

$workflow->addWriter([
    'writer' => $writer1,
    'filter' => function ($item) { return $item['year'] < 2010; },
]);
$workflow->addWriter([
    'writer' => $writer2,
    'filter' => function ($item) { return $item['year'] >= 2010; },
]);

Default Writers

The core Plum package currently contains only ArrayWriter.

ArrayWriter

The Plum\Plum\Writer\ArrayWriter writes the data into an array that can be retrieved using the getData() method.

use Plum\Plum\Writer\ArrayWriter;

$writer = new ArrayWriter();
// Workflow processing
$writer->getData() // -> [...]

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Index Workflow Readers Writers Filters Converters Extensions