README

Installation

You can install the package via composer:

composer require digiservnet/data-transfer-object

Usage

The goal of this package is to make constructing objects from arrays of (serialized) data as easy as possible. Here's what a DTO looks like:

use Digiservnet\DataTransferObject\Attributes\MapFrom;
use Digiservnet\DataTransferObject\DataTransferObject;

class MyDTO extends DataTransferObject
{
    public OtherDTO $otherDTO;
    
    public OtherDTOCollection $collection;
    
    #[CastWith(ComplexObjectCaster::class)]
    public ComplexObject $complexObject;
    
    public ComplexObjectWithCast $complexObjectWithCast;
    
    #[NumberBetween(1, 100)]
    public int $a;
    
    #[MapFrom('address.city')]
    public string $city;
}

You could construct this DTO like so:

$dto = new MyDTO(
    a: 5,
    collection: [
        ['id' => 1],
        ['id' => 2],
        ['id' => 3],
    ],
    complexObject: [
        'name' => 'test',
    ],
    complexObjectWithCast: [
        'name' => 'test',
    ],
    otherDTO: ['id' => 5],
);

Let's discuss all possibilities one by one.

Named arguments

Constructing a DTO can be done with named arguments. It's also possible to still use the old array notation. This example is equivalent to the one above.

$dto = new MyDTO([
    'a' => 5,
    'collection' => [
        ['id' => 1],
        ['id' => 2],
        ['id' => 3],
    ],
    'complexObject' => [
        'name' => 'test',
    ],
    'complexObjectWithCast' => [
        'name' => 'test',
    ],
    'otherDTO' => ['id' => 5],
]);

Value casts

If a DTO has a property that is another DTO or a DTO collection, the package will take care of automatically casting arrays of data to those DTOs:

$dto = new MyDTO(
    collection: [ // This will become an object of class OtherDTOCollection
        ['id' => 1],
        ['id' => 2], // Each item will be an instance of OtherDTO
        ['id' => 3],
    ],
    otherDTO: ['id' => 5], // This data will be cast to OtherDTO
);

Custom casters

You can build your own caster classes, which will take whatever input they are given, and will cast that input to the desired result.

Take a look at the ComplexObject:

class ComplexObject
{
    public string $name;
}

And its caster ComplexObjectCaster:

use Digiservnet\DataTransferObject\Caster;

class ComplexObjectCaster implements Caster
{
    /**
     * @param array|mixed $value
     *
     * @return mixed
     */
    public function cast(mixed $value): ComplexObject
    {
        return new ComplexObject(
            name: $value['name']
        );
    }
}

Class-specific casters

Instead of specifying which caster should be used for each property, you can also define that caster on the target class itself:

class MyDTO extends DataTransferObject
{
    public ComplexObjectWithCast $complexObjectWithCast;
}

#[CastWith(ComplexObjectWithCastCaster::class)]
class ComplexObjectWithCast
{
    public string $name;
}

Default casters

It's possible to define default casters on a DTO class itself. These casters will be used whenever a property with a given type is encountered within the DTO class.

#[
    DefaultCast(DateTimeImmutable::class, DateTimeImmutableCaster::class),
    DefaultCast(MyEnum::class, EnumCaster::class),
]
abstract class BaseDataTransferObject extends DataTransferObject
{
    public MyEnum $status; // EnumCaster will be used
    
    public DateTimeImmutable $date; // DateTimeImmutableCaster will be used
}

Using custom caster arguments

Any caster can be passed custom arguments, the built-in ArrayCaster implementation is a good example of how this may be used.

Using named arguments when passing input to your caster will help make your code more clear, but they are not required.

For example:

    /** @var \Digiservnet\DataTransferObject\Tests\Foo[] */
    #[CastWith(ArrayCaster::class, itemType: Foo::class)]
    public array $collectionWithNamedArguments;
    
    /** @var \Digiservnet\DataTransferObject\Tests\Foo[] */
    #[CastWith(ArrayCaster::class, Foo::class)]
    public array $collectionWithoutNamedArguments;

Note that the first argument passed to the caster constructor is always the array with type(s) of the value being casted. All other arguments will be the ones passed as extra arguments in the CastWith attribute.

Validation

This package doesn't offer any specific validation functionality, but it does give you a way to build your own validation attributes. For example, NumberBetween is a user-implemented validation attribute:

class MyDTO extends DataTransferObject
{
    #[NumberBetween(1, 100)]
    public int $a;
}

It works like this under the hood:

#[Attribute(Attribute::TARGET_PROPERTY | Attribute::IS_REPEATABLE)]
class NumberBetween implements Validator
{
    public function __construct(
        private int $min,
        private int $max
    ) {
    }

    public function validate(mixed $value): ValidationResult
    {
        if ($value < $this->min) {
            return ValidationResult::invalid("Value should be greater than or equal to {$this->min}");
        }

        if ($value > $this->max) {
            return ValidationResult::invalid("Value should be less than or equal to {$this->max}");
        }

        return ValidationResult::valid();
    }
}

Mapping

You can map a DTO property from a source property with a different name using the #[MapFrom] attribute.

It works with a "dot" notation property name or an index.

class PostDTO extends DataTransferObject
{
    #[MapFrom('postTitle')]
    public string $title;
    
    #[MapFrom('user.name')]
    public string $author;
}

$dto = new PostDTO([
    'postTitle' => 'Hello world',
    'user' => [
        'name' => 'John Doe'
    ]
]);

class UserDTO extends DataTransferObject
{

    #[MapFrom(0)]
    public string $firstName;
    
    #[MapFrom(1)]
    public string $lastName;
}

$dto = new UserDTO(['John', 'Doe']);

Sometimes you also want to map them during the transformation to Array. A typical usecase would be transformation from camel case to snake case. For that you can use the #[MapTo] attribute.

class UserDTO extends DataTransferObject
{

    #[MapFrom(0)]
    #[MapTo('first_name')]
    public string $firstName;
    
    #[MapFrom(1)]
    #[MapTo('last_name')]
    public string $lastName;
}

$dto = new UserDTO(['John', 'Doe']);
$dto->toArray() // ['first_name' => 'John', 'last_name'=> 'Doe'];
$dto->only('first_name')->toArray() // ['first_name' => 'John'];

Strict DTOs

The previous version of this package added the FlexibleDataTransferObject class which allowed you to ignore properties that didn't exist on the DTO. This behaviour has been changed, all DTOs are flexible now by default, but you can make them strict by using the #[Strict] attribute:

class NonStrictDto extends DataTransferObject
{
    public string $name;
}

// This works
new NonStrictDto(
    name: 'name',
    unknown: 'unknown'
);

use \Digiservnet\DataTransferObject\Attributes\Strict;

#[Strict]
class StrictDto extends DataTransferObject
{
    public string $name;
}

// This throws a \Digiservnet\DataTransferObject\Exceptions\UnknownProperties exception
new StrictDto(
    name: 'name',
    unknown: 'unknown'
);

Helper functions

There are also some helper functions provided for working with multiple properties at once.

$postData->all();

$postData
    ->only('title', 'body')
    ->toArray();
    
$postData
    ->except('author')
    ->toArray();

Note that all() will simply return all properties, while toArray() will cast nested DTOs to arrays as well.

You can chain the except() and only() methods:

$postData
    ->except('title')
    ->except('body')
    ->toArray();

It's important to note that except() and only() are immutable, they won't change the original data transfer object.

Immutable DTOs and cloning

This package doesn't force immutable objects since PHP doesn't support them, but you're always encouraged to keep your DTOs immutable. To help you, there's a clone method on every DTO which accepts data to override:

$clone = $original->clone(other: ['name' => 'a']);

Note that no data in $original is changed.

Collections of DTOs

This version removes the DataTransferObjectCollection class. Instead you can use simple casters and your own collection classes.

Here's an example of casting a collection of DTOs to an array of DTOs:

class Bar extends DataTransferObject
{
    /** @var \Digiservnet\DataTransferObject\Tests\Foo[] */
    #[CastWith(FooArrayCaster::class)]
    public array $collectionOfFoo;
}

class Foo extends DataTransferObject
{
    public string $name;
}

class FooArrayCaster implements Caster
{
    public function cast(mixed $value): array
    {
        if (! is_array($value)) {
            throw new Exception("Can only cast arrays to Foo");
        }

        return array_map(
            fn (array $data) => new Foo(...$data),
            $value
        );
    }
}

If you don't want the redundant typehint, or want extended collection functionality; you could create your own collection classes using any collection implementation. In this example, we use Laravel's:

class Bar extends DataTransferObject
{
    #[CastWith(FooCollectionCaster::class)]
    public CollectionOfFoo $collectionOfFoo;
}

class Foo extends DataTransferObject
{
    public string $name;
}

use Illuminate\Support\Collection;

class CollectionOfFoo extends Collection
{
    // Add the correct return type here for static analyzers to know which type of array this is 
    public function offsetGet($key): Foo
    {
        return parent::offsetGet($key);
    }
}

class FooCollectionCaster implements Caster
{
    public function cast(mixed $value): CollectionOfFoo
    {
        return new CollectionOfFoo(array_map(
            fn (array $data) => new Foo(...$data),
            $value
        ));
    }
}

Simple arrays of DTOs

For a simple array of DTOs, or an object that implements PHP's built-in ArrayAccess, consider using the ArrayCaster which requires an item type to be provided:

class Bar extends DataTransferObject
{
    /** @var \Digiservnet\DataTransferObject\Tests\Foo[] */
    #[CastWith(ArrayCaster::class, itemType: Foo::class)]
    public array $collectionOfFoo;
}

Testing

composer test

Changelog

Please see CHANGELOG for more information on what has changed recently.

Contributing

Please see CONTRIBUTING for details.

Security

If you've found a bug regarding security please mail ian.h@digiserv.net instead of using the issue tracker.

External tools

json2dto: a GUI to convert JSON objects to DTO classes (with nesting support). Also provides a CLI tool for local usage.
Data Transfer Object Factory: Intelligently generates a DTO instance using the correct content for your properties based on its name and type.

Credits

Our Arr class contains functions copied from Laravels Arr helper.

License

The MIT License (MIT). Please see License File for more information.

digiservnet / data-transfer-object

Maintainers

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