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Validation

The source given to a mapper can never be trusted, this is actually the very goal of this library: transforming an unstructured input to a well-defined object structure. If the mapper cannot guess how to cast a certain value, it means that it is not able to guarantee the validity of the desired object thus it will fail.

Any issue encountered during the mapping will add an error to an upstream exception of type \CuyZ\Valinor\Mapper\MappingError. It is therefore always recommended wrapping the mapping function call with a try/catch statement and handle the error properly.

More specific validation should be done in the constructor of the value object, by throwing an exception if something is wrong with the given data. A good practice would be to use lightweight validation tools like Webmozart Assert.

When the mapping fails, the exception gives access to the root node. This recursive object allows retrieving all needed information through the whole mapping tree: path, values, types and messages, including the issues that caused the exception.

final class SomeClass
{
    public function __construct(private string $someValue)
    {
        Assert::startsWith($someValue, 'foo_');
    }
}

try {
   (new \CuyZ\Valinor\MapperBuilder())
        ->mapper()
        ->map(
            SomeClass::class,
            ['someValue' => 'bar_baz']
        );
} catch (\CuyZ\Valinor\Mapper\MappingError $error) {
    // Get flatten list of all messages through the whole nodes tree
    $node = $error->node();
    $messages = new \CuyZ\Valinor\Mapper\Tree\Message\MessagesFlattener($node);

    // If only errors are wanted, they can be filtered
    $errorMessages = $messages->errors();

    // Should print something similar to:
    // > Expected a value to start with "foo_". Got: "bar_baz"
    foreach ($errorMessages as $message) {
        echo $message;
    }
}
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