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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)
• 🔒 Immutable DTOs with readonly properties
• ♻️ Consistent data shape enforcement across boundaries

📦 Installation

Install via Composer:

🚀 Quick Start

1. Define a DTO

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

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

2. Create an Assembler

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

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

3. Assemble a DTO

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

You can also batch transform arrays or collections:

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

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

ProductDTO with nested casting:

ProductDTOAssembler mapping input structure:

🎯 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.

Registering the Assembler

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.

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.

🎯 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:

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:

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

🔒 Immutable DTOs

For scenarios where data integrity is critical, ArgonautImmutableDTO provides a base class for creating DTOs with readonly properties that cannot be modified after construction.

When to Use Immutable DTOs

• API Responses: Ensure response data remains unchanged throughout the request lifecycle
• Event Sourcing: Immutable events that represent facts that happened
• Value Objects: Data that should never change once created
• Thread Safety: Prevent accidental mutations in concurrent operations
• Functional Patterns: Enable predictable, side-effect-free code

Defining an Immutable DTO

Usage

Immutable DTOs with Assemblers

Immutable DTOs work seamlessly with assemblers:

Nested Immutable DTOs

Immutable DTOs support all casting features including nested DTOs:

Comparison: Mutable vs Immutable

Note: Choose ArgonautDTO when you need mutable objects with custom setters. Choose ArgonautImmutableDTO when you want guaranteed immutability and don't need post-construction modifications.

🎯 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.

🔁 Casting Reference

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

BackedEnum Casting

PHP BackedEnum types are automatically detected and cast using Enum::from(). Existing enum instances are passed through unchanged. On serialization, enums are converted back to their backing value.

✅ Validation

Validate DTOs with Laravel’s validator:

📤 Serialization

Serialize DTOs for output, API responses, etc.

Partial Serialization

Use only() and except() to serialize a subset of properties:

🔄 Merging Attributes

Mutable DTOs support merging additional attributes after construction:

merge() returns the same instance, so it can be chained:

Note: merge() is only available on ArgonautDTO. Immutable DTOs do not support post-construction modification.

🧩 Trait-Based Architecture

Under the hood, both ArgonautDTO and ArgonautImmutableDTO compose shared behavior from three traits:

This is transparent to most users, but if you are extending internal behavior (e.g., overriding castInputValue() in a subclass), note that these methods now live in traits rather than directly on the base class. Method resolution is identical for inheritance purposes.

🛠️ DTO Collection Helper

Create DTO collections directly:

🧪 Testing

Run the test suite:

Run tests with coverage report:

Run static analysis (PHPStan):

Run code style fixer (Pint):

📚 Credits

• Yorda
• All Contributors

📃 License

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