dynamically add new Entry to row

[azngeek]

I do have one requirement where i need to add a new entry after a transformation. The pseudo-code would be something like this.

 public function transform(Rows $rows): Rows
            {
                foreach ($rows as $row) {
                    $entries = $row->entries();

                    // This will return a new entries object
                    $newEntries = $entries->add(new Row\Entry\StringEntry('name', 'Blabla'));

                    // The newEntries variable can not be used within the Rows-object. It would be great to have the option
                    // to dynamically add a new entry to an existing row.
                }
                return $rows;
            }

It seems like this is not a supported case at the moment. What i do instead is to create a new Rows-object instead. So something like this:

   public function transform(Rows $rows): Rows
            {
                foreach ($rows as $row) {
                    return new Rows(Row::create(
                        Entry::integer('name', '')
                    ));
                }
            }

[norberttech]

Hey, not sure if I fully understand your use case, could you maybe provide example of what you are trying to achieve in following format:

before:

[
   ['entry_a' => 'value', 'entry_b' => 'value'],
   ['entry_a' => 'value', 'entry_b' => 'value']
]

after:

[
   ['entry_a' => 'value', 'entry_b' => 'value', 'extra_value' => 1],
   ['entry_a' => 'value', 'entry_b' => 'value', 'extra_value' => 1],
]

[azngeek]

This is exactly what i am trying to do. I want to add a new entry to the existing row. However if i call this method $entries->add() the new entry will not be referenced in the existing Row.

 public function transform(Rows $rows): Rows
            {
                foreach ($rows as $row) {
                    $entries = $row->entries();

                    // This will return a new entries object
                    $newEntries = $entries->add(new Row\Entry\StringEntry('extra_value', '1'));

                    // The newEntries variable can not be used within the Rows-object. It would be great to have the option
                    // to dynamically add a new entry to an existing row.
                }
                return $rows;
            }

[norberttech]

Oh I see, so here are a few examples of how you can achieve it.
You were almost good, but you need to remember that Rows is immutable, which means that while iterating using foreach even if you change something at a single Row it wont affect Rows.
To adjust Rows you should use Rows::map(static fn (Row $row) : Row => $row) that will return a new instance of Rows that would include your changes at each Row you made through the anonymous function.

<?php

use Flow\ETL\DSL\Entry;
use Flow\ETL\DSL\From;
use Flow\ETL\DSL\To;
use Flow\ETL\DSL\Transform;
use Flow\ETL\Flow;
use Flow\ETL\Memory\ArrayMemory;
use Flow\ETL\Row;
use Flow\ETL\Rows;
use Flow\ETL\Transformer;

require __DIR__ . '/../vendor/autoload.php';

(new Flow())
    ->read(From::array(
        [
            ['entry_a' => 'value', 'entry_b' => 'value'],
            ['entry_a' => 'value', 'entry_b' => 'value']
        ]
    ))
    ->rows(Transform::array_unpack('row'))
    ->drop('row')
    ->write(To::stdout())
    ->rows(Transform::add_integer('extra_value', \random_int(1, 5)))
    ->write(To::stdout())
    ->run();

(new Flow())
    ->read(From::array(
        [
            ['entry_a' => 'value', 'entry_b' => 'value'],
            ['entry_a' => 'value', 'entry_b' => 'value']
        ]
    ))
    ->rows(Transform::array_unpack('row'))
    ->drop('row')
    ->write(To::stdout())
    ->map(static fn (Row $row) : Row => $row->add(Entry::integer('extra_value', \random_int(1, 5))))
    ->write(To::stdout())
    ->run();

(new Flow())
    ->read(From::array(
        [
            ['entry_a' => 'value', 'entry_b' => 'value'],
            ['entry_a' => 'value', 'entry_b' => 'value']
        ]
    ))
    ->rows(Transform::array_unpack('row'))
    ->drop('row')
    ->write(To::stdout())
    ->transform(
        new class implements Transformer {
            public function transform(Rows $rows): Rows
            {
                return $rows->map(function (Row $row) : Row {
                    return $row->add(Entry::integer('extra_value', \random_int(1, 10)));
                });
            }

            public function __unserialize(array $data): void
            {
            }

            public function __serialize(): array
            {
                return [];
            }
        }
    )
    ->write(To::stdout())
    ->run();

Let me know if that solves your problem, output of above script, below:

+-------+-------+
|entry_a|entry_b|
+-------+-------+
|  value|  value|
|  value|  value|
+-------+-------+
2 rows
+-------+-------+-----------+
|entry_a|entry_b|extra_value|
+-------+-------+-----------+
|  value|  value|          2|
|  value|  value|          2|
+-------+-------+-----------+
2 rows
+-------+-------+
|entry_a|entry_b|
+-------+-------+
|  value|  value|
|  value|  value|
+-------+-------+
2 rows
+-------+-------+-----------+
|entry_a|entry_b|extra_value|
+-------+-------+-----------+
|  value|  value|          3|
|  value|  value|          4|
+-------+-------+-----------+
2 rows
+-------+-------+
|entry_a|entry_b|
+-------+-------+
|  value|  value|
|  value|  value|
+-------+-------+
2 rows
+-------+-------+-----------+
|entry_a|entry_b|extra_value|
+-------+-------+-----------+
|  value|  value|          7|
|  value|  value|         10|
+-------+-------+-----------+
2 rows

[azngeek]

This examples helped me a lot. However i think i will go with the last approach using the custom transformer as it better fits my scenario.