callback.md

Callback transformer

The callback transformer helps quickly set up transformers for data streams that have no generic implementation.

<?php
use ZeroConfig\Cli\Transformer\Callback\CallbackTransformer;
use ZeroConfig\Cli\Transformer\TransformerChain;
use ZeroConfig\Cli\Transformer\String\LineEnding;
use ZeroConfig\Cli\Writer\File;

$doubler = new CallbackTransformer(
    function (iterable $prices) : iterable {
        foreach ($prices as $price) {
            yield sprintf('%.2f', $price * 2);
        }
    }
);

$writer = new File('price-feed.txt');

$transformer = new TransformerChain(
    $doubler,
    new LineEnding()
);

$prices = ['12.34', '56.00'];

$writer($transformer($prices));

The contents of price-feed.txt will be:

24.68
112.00

Further reading

See other available transformers.