Laravel Argonaut DTO

Laravel Argonaut DTO is a lightweight, highly composable package for transforming arrays, objects, or collections into structured DTOs (Data Transfer Objects), with built-in support for:

• 🧱 Deep nested transformation and casting
• 🔁 Type-safe data conversion
• ✅ Validation using Laravel’s validator
• 🧠 Explicit attribute prioritization
• 📦 Clean serialization (toArray, toJson)
• ♻️ Consistent data shape enforcement across boundaries

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📦 Installation

Install via Composer:

composer require yorcreative/laravel-argonaut-dto

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🚀 Quick Start

1. Define a DTO

DTOs extend ArgonautDTO, and define your expected structure via public properties, casting rules, and validation.

class UserDTO extends ArgonautDTO
{
    public string $username;
    public string $email;

    protected array $casts = [
        'username' => 'string',
        'email' => 'string',
    ];

    public function rules(): array
    {
        return [
            'username' => ['required', 'string'],
            'email' => ['required', 'email'],
        ];
    }
}

This defines a strongly typed DTO with both validation rules and simple type casting.

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2. Create an Assembler

Assemblers are responsible for mapping raw inputs (arrays or objects) into your DTOs.

// static usage example
class UserDTOAssembler extends ArgonautAssembler
{
    public static function toUserDTO(object $input): UserDTO
    {
        return new UserDTO([
            'username' => $input->display_name,
            'email' => $input->email,
        ]);
    }
}

// instance usage example
class UserDTOAssembler extends ArgonautAssembler
{
    public function __construct(protected UserFormattingService $formattingService) 
    {
        //
    }
    
    public static function toUserDTO(object $input): UserDTO
    {
        return new UserDTO([
            'username' => $formatingService->userName($input->display_name),
            'email' => $formatingService->email($input->email),
        ]);
    }
}

Assembler method names must follow the format to<ClassName> or from<ClassName>, and are resolved automatically using class_basename.

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3. Assemble a DTO

Use the assembler to transform raw data into structured, casted DTO instances.

// static usage example
$dto = UserDTOAssembler::assemble([
    'display_name' => 'jdoe',
    'email' => '[email protected]',
], UserDTO::class);

// instance usage example
$dto = $userDTOAssemblerInstance->assembleInstance([
    'display_name' => 'jdoe',
    'email' => '[email protected]',
], UserDTO::class);

You can also batch transform arrays or collections:

// static usage
UserDTOAssembler::fromArray($userArray, UserDTO::class);
UserDTOAssembler::fromCollection($userCollection, UserDTO::class);

// instance usage
UserDTOAssembler::fromArray($userArray, UserDTO::class, $userDTOAssemblerInstance);
UserDTOAssembler::fromCollection($userCollection, UserDTO::class, $userDTOAssemblerInstance);

// or using the assembler instance's static methods
$userDTOAssemblerInstance::fromArray($userArray, UserDTO::class, $userDTOAssemblerInstance);
$userDTOAssemblerInstance::fromCollection($userCollection, UserDTO::class, $userDTOAssemblerInstance);

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🧪 Real-World Static Usage Example: Product + Features + Reviews

This example demonstrates nested relationships and complex type casting in action.

ProductDTO with nested casting:

class ProductDTO extends ArgonautDTO
{
    public string $title;
    public array $features;
    public Collection $reviews;
    public ?UserDTO $user = null;

    protected array $casts = [
        'features' => [ProductFeatureDTO::class],
        'reviews' => Collection::class . ':' . ProductReviewDTO::class,
        'user' => UserDTO::class,
    ];

    public function rules(): array
    {
        return [
            'title' => ['required', 'string'],
            'reviews' => ['sometimes', 'required', 'collection', 'min:1'],
        ];
    }
}

ProductDTOAssembler mapping input structure:

class ProductDTOAssembler extends ArgonautAssembler
{
    public static function toProductDTO(object $input): ProductDTO
    {
        return new ProductDTO([
            'title' => $input->product_name,
            'user' => $input->user,
            'features' => $input->features ?? [],
            'reviews' => $input->reviews ?? [],
        ]);
    }

    public static function toProductFeatureDTO(object $input): ProductFeatureDTO
    {
        return new ProductFeatureDTO([
            'name' => $input->name ?? 'Unnamed Feature',
            'description' => $input->description ?? null,
        ]);
    }

    public static function toProductReviewDTO(object $input): ProductReviewDTO
    {
        return new ProductReviewDTO([
            'rating' => (int) ($input->rating ?? 0),
            'comment' => $input->comment ?? '',
        ]);
    }
}

🎯 Dependency Injection in Assemblers

ArgonautAssembler offers enhanced flexibility for your Assembler logic by supporting dependency injection. This allows you to leverage services or custom logic, whether defined in static or non-static methods, during the DTO assembly process. This is particularly powerful when integrating with Laravel's service container.

This feature enables you to:

• Integrate Application Services: Easily inject your existing application services (e.g., a custom formatting utility, a validation service) directly into your assembler methods.
• Decouple Complex Logic: Keep your assembler methods focused on the core task of data mapping by delegating more complex operations or external data fetching/processing to injected dependencies.
• Improve Testability: By injecting dependencies, you can more easily mock them in your unit tests, leading to more robust and isolated tests for your assemblers.

How Dependency Injection Works

ArgonautAssembler supports dependency injection in non-static transformation methods (e.g., toUserDTO or fromUserDTO) by leveraging Laravel’s service container. When you call ArgonautAssembler::assemble(), fromCollection(), fromArray(), or assembleInstance() with an instance of the assembler, the transformation method is invoked on that instance. Laravel’s container automatically resolves and injects any dependencies declared in the method’s signature.

• Static Methods: Static transformation methods (e.g., public static function toUserDTO($input)) do not support dependency injection, as they are called statically without an instance.
• Instance Methods: Non-static transformation methods (e.g., public function toUserDTO($input)) are called on an assembler instance, allowing Laravel to inject dependencies into the method.

Example: Using Dependency Injection

Below is an example of an assembler with a non-static transformation method that uses dependency injection to format a user’s name via an injected service.

<?php

namespace App\Assemblers;

use App\DTOs\UserDTO;
use App\Services\UserFormattingService;
use YorCreative\LaravelArgonautDTO\ArgonautAssembler;

class UserAssembler extends ArgonautAssembler
{
    public function __construct(protected UserFormattingService $formattingService) 
    {
        //
    }
    
    /**
     * Transform input data into a UserDTO with dependency injection.
     *
     * @param object $input Input data (e.g., from a model or array cast to object).
     * @param UserFormattingService $formatter Injected service for formatting user data.
     * @return UserDTO
     */
    public function toUserDTO(object $input): UserDTO
    {
        return new UserDTO([
            'full_name' => $formattingService->formatName($input->first_name, $input->last_name),
            'email' => $input->email,
            'created_at' => $input->created_at,
        ]);
    }
}

Registering the Assembler

// ServiceProvider
<?php

namespace App\Providers;

use Illuminate\Support\ServiceProvider;

class YourServiceProvider extends ServiceProvider
{
    public function register()
    {
        $this->app->bind(FormattingServiceInterface::class, function($app) {
            return new FormattingService();
        })
         $this->app->bind(YourArgonautAssembler::clas, function ($app) {
             return new YourArgonautAssembler($app->get(FormattingServiceInterface::class));
         });
    }

    public function provides()
    {
        return [
               YourArgonautAssembler::class,
               FormattingServiceInterface::class
        ]       
    }
}

Using the Assembler

To use the assembler with dependency injection, you need to provide an instance of the assembler to the assemble method or related methods (fromCollection, fromArray, or assembleInstance). Laravel’s container will resolve the dependencies when the method is invoked.

<?php

use App\Assemblers\UserAssembler;
use App\DTOs\UserDTO;

// Example input (e.g., a model or object)
$input = (object) [
    'first_name' => 'John',
    'last_name' => 'Doe',
    'email' => '[email protected]',
    'created_at' => now(),
];

// Creating an assembler instance
$formattingService = new UserFormattingService();
$assembler = new UserAssembler($formattingService);
// or using the container instance
$assembler = resolve(YourArgonautAssembler::class);

// Pass the $assembler instance 
$userDTO = UserAssembler::assemble($input, UserDTO::class, $assembler);
// Or use the instance method
$userDTO = $assembler->assembleInstance($input, UserDTO::class);

// Transform a collection passing the $assembler instance
$array = [$input, $input];
$collection = collect($array);
$userDTOs = UserAssembler::fromCollection($collection, UserDTO::class, $assembler);
$userDTOs = $assembler::fromArray($array, UserDTO::class, $assembler)

In this example:

• The toUserDTO method requires a UserFormattingService dependency.
• The assembler instance ($assembler) is passed to assemble, fromArray or fromCollection, ensuring the non-static toUserDTO method is invoked on the instance.

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🎯 Nested Assemblers for Deep Transformations

Nested assemblers enhance the casting process by allowing you to specify an assembler class for individual fields in your DTO. When a value is assigned to that field during construction or attribute setting, the raw input is first passed through the assembler's transformation method (e.g., toUserDTO) before the cast is applied. This is ideal for handling complex, nested data structures where raw inputs need preprocessing or mapping.

Nested assemblers integrate seamlessly with casting:

• For single casts (e.g., UserDTO::class), the assembler transforms the input value directly.
• For array or collection casts (e.g., [ProductFeatureDTO::class] or Collection::class . ':' . ProductReviewDTO::class), the assembler is applied to each item in the iterable value.
• Assemblers used in nested contexts must have static transformation methods, as they are invoked statically without an instance.

Defining Nested Assemblers

Add a protected array $nestedAssemblers property to your DTO, mapping field names to assembler classes:

class ProductDTO extends ArgonautDTO
{
    public string $title;
    public array $features;
    public Collection $reviews;
    public ?UserDTO $user = null;

    protected array $casts = [
        'features' => [ProductFeatureDTO::class],
        'reviews' => Collection::class . ':' . ProductReviewDTO::class,
        'user' => UserDTO::class,
    ];

    protected array $nestedAssemblers = [
        'user' => UserDTOAssembler::class
    ];

    public function rules(): array
    {
        return [
            'title' => ['required', 'string'],
            'reviews' => ['sometimes', 'required', 'collection', 'min:1'],
        ];
    }
}

In this example:

• The user field will use UserDTOAssembler::toUserDTO() (or fromUserDTO()) to transform raw input (e.g., an array or object with display_name and email) before casting it to a UserDTO instance.
• If added, features or reviews would apply the assembler to each item in the array/collection.

How It Works

When setting attributes (via constructor or setAttributes):

1. If a nested assembler is defined for the key and a cast exists, the assembler transforms the value (or each item for iterables).
2. The transformed value is then cast according to $casts (e.g., into a DTO, collection, etc.).
3. Scalars (non-array/object values) skip the assembler to avoid type errors.

This ensures deep, automatic transformations while maintaining type safety and structure.

Example Usage

With the above ProductDTO and a raw input:

$rawProduct = [
    'title' => 'Standing Desk',
    'user' => ['display_name' => 'jdoe', 'email' => '[email protected]'],
    'features' => [['name' => 'Height Adjustable']],
    'reviews' => [['rating' => 5, 'comment' => 'Great!']],
];

$productDTO = ProductDTOAssembler::assemble($rawProduct, ProductDTO::class);

// $productDTO->user is now a fully assembled UserDTO instance
$this->assertInstanceOf(UserDTO::class, $productDTO->user);
$this->assertSame('jdoe', $productDTO->user->username);

Nested assemblers promote composability, making it easier to handle multi-layered data in APIs, services, or complex domain logic.

🎯 DTOs with Prioritized Attributes and Custom Setters

ArgonautDTO allows you to prioritize the assignment of specific fields using $prioritizedAttributes, which is critical for cases where one field influences others.

class UserDTO extends ArgonautDTO
{
    public ?string $firstName = null;
    public ?string $lastName = null;
    public string $username;
    public string $email;
    public ?string $fullName = null;

    protected array $prioritizedAttributes = ['firstName', 'lastName'];

    protected array $casts = [
        'firstName' => 'string',
        'lastName' => 'string',
        'username' => 'string',
        'email' => 'string',
        'fullName' => 'string',
    ];

    public function setFirstName($value)
    {
        $this->firstName = $value;
        $this->fullName = $this->firstName . ' ' . $this->lastName;
    }

    public function setLastName($value)
    {
        $this->lastName = $value;
        $this->fullName = $this->firstName . ' ' . $this->lastName;
    }

    public function rules(): array
    {
        return [
            'firstName' => ['nullable', 'string', 'max:32'],
            'lastName' => ['nullable', 'string', 'max:32'],
            'username' => ['required', 'string', 'max:64'],
            'email' => ['required', 'email', 'max:255'],
        ];
    }
}

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🔁 Casting Reference

Casting allows you to automatically transform values into other DTOs, Laravel Collections, arrays, dates, and more.

protected array $casts = [
    'registeredAt' => \Illuminate\Support\Carbon::class,
    'profile' => ProfileDTO::class,
    'roles' => [RoleDTO::class],
    'permissions' => Collection::class . ':' . PermissionDTO::class,
];

Cast Type	Example	Description
Scalar	'string', 'int', etc.	Native PHP type cast
Single DTO	ProfileDTO::class	Cast an array to a DTO instance
Array of DTOs	[RoleDTO::class]	Cast to array of DTOs
Collection of DTOs	Collection::class . ':' . CommentDTO::class	Cast to a Laravel Collection
Date casting	Carbon::class	Cast to Carbon/DateTime instance

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✅ Validation

Validate DTOs with Laravel’s validator:

$userDTO->validate();         // Throws ValidationException
$userDTO->validate(false);    // Returns array of errors (non-throwing)
$userDTO->isValid();          // Returns true/false

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📤 Serialization

Serialize DTOs for output, API responses, etc.

$userDTO->toArray(); // Recursively converts nested DTOs
$userDTO->toJson();  // JSON output (throws on encoding errors)

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🛠️ DTO Collection Helper

Create DTO collections directly:

UserDTO::collection([
    ['username' => 'john', 'email' => '[email protected]'],
]);

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🧪 Testing

Run the test suite using:

composer test

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📚 Credits

• Yorda
• All Contributors

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📃 License

This package is open-sourced software licensed under the MIT license.