[Serializer] Introduce the concept of AttributeTransformer #15761

dosten · 2015-09-11T03:59:09Z

Hi folks!

In a recent project I found that if some define a callback when normalize a object (i.e. Convert a DateTime object to a ISO8601 string) there isn't a easy way to convert the ISO8601 string into a DateTime object, so, I propose to introduce the concept of AttributeTransformers as a replacement of the concept of callbacks.
The idea is very similar to the concept of DataTransformers in the Form component.
We would have a interface that should be implemented by all transformers:

<?php

namespace Symfony\Component\Serializer;

interface AttributeTransformerInterface
{
    public function transform($value);
    public function reverseTransform($value);
}

The transform method will be called in the normalization (Similar to the current behavior).
The reverseTransform will be called in the denormalization.

This will require a new method AbstractNormalizer::setTransformer($attribute, AttributeTransformerInterface $transformer).

IMO this can be implemented in a BC way, the idea is deprecate the concept of callbacks in favor of the concept of attribute transformers.

The text was updated successfully, but these errors were encountered:

derrabus · 2015-09-14T13:30:56Z

What would be the difference between a normalizer and a transformer in this context?

dosten · 2015-09-14T14:24:15Z

The normalizer converts a whole object into an array, a transformer convert a single property of this object into any thing you want (i.e A DateTime object into a ISO8601 string). Think that a transformer is an extended version of the "callbacks" provided by normalizers (http://symfony.com/doc/current/components/serializer.html#using-callbacks-to-serialize-properties-with-object-instances) but the callbacks only works in the normalization, if you want to denormalize an array into an object, you can't.

derrabus · 2015-09-14T14:39:07Z

I see. But if I had a normalizer that handles DateTime instances and a mechanism to indicate the type of a certain property (like described in #14844 for instance), would I still need those transformers?

dunglas · 2015-09-21T15:19:14Z

We do it the same way as described by @derrabus in API Platform: https://github.com/dunglas/DunglasApiBundle/blob/master/JsonLd/Serializer/DateTimeNormalizer.php

dunglas added the Serializer label Sep 21, 2015

dosten closed this as completed Nov 28, 2015

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[Serializer] Introduce the concept of AttributeTransformer #15761

[Serializer] Introduce the concept of AttributeTransformer #15761

[Serializer] Introduce the concept of AttributeTransformer #15761

[Serializer] Introduce the concept of AttributeTransformer #15761

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