Creating a transformer

Transformers take complex values and transform them into simple types. For example, a Carbon object could be transformed to 16-05-1994T00:00:00+00.

A transformer implements the following interface:

interface Transformer
{
    public function transform(DataProperty $property, mixed $value, TransformationContext $context): mixed;
}

The following parameters are provided:

• property: a DataProperty object which represents the property for which the value is transformed. You can read more about the internal structures of the package here
• value: the value that should be transformed, this will never be null
• context: a TransformationContext object which contains the current transformation context with the following properties:
  • transformValues indicates if values should be transformed or not
  • mapPropertyNames indicates if property names should be mapped or not
  • wrapExecutionType the execution type that should be used for wrapping values
  • transformers a collection of transformers that can be used to transform values

In the end, the transformer should return a transformed value.

##Combining transformers and casts

You can transformers and casts in one class:

class ToUpperCastAndTransformer implements Cast, Transformer
{
    public function cast(DataProperty $property, mixed $value, array $properties, CreationContext $context): string
    {
        return strtoupper($value);
    }
    
    public function transform(DataProperty $property, mixed $value, TransformationContext $context): string
    {
        return strtoupper($value);
    }
}

Within your data object, you can use the WithCastAndTransformer attribute to use the cast and transformer:

class SongData extends Data
{
    public function __construct(
        public string $title,
        #[WithCastAndTransformer(SomeCastAndTransformer::class)]
        public string $artist,
    ) {
    }
}