🛸Data Transfer Objects

When building API integrations, sometimes dealing with a raw response or a JSON response can be tedious and unpredictable. Data transfer objects are a good solution as they allow you to define a structure for a request and response. Saloon supports casting a response from an API request into a DTO.

Defining DTOs from responses

In your request, extend the createDtoFromResponse method. Within this method, you get access to the Response object containing the response to cast into a data transfer object.

<?php

use Saloon\Http\Request;
use Saloon\Http\Response;

class GetServerRequest extends Request
{
    // {...}
    
    public function createDtoFromResponse(Response $response): mixed
    {
        $data = $response->json();
    
        return new Server(
            id: $data['id'],
            name: $data['name'],
            ipAddress: $data['ip'],
        );
    }
}

This is what the Server DTO looks like:

<?php

class Server
{
    public function __construct(
        public readonly int $id,
        public readonly string $name,
        public readonly string $ipAddress,
    ){}
}

Retrieving your DTO from responses

Now we have defined our DTO on our request or connector, we can use the build in dto or dtoOrFail methods on our response class.

<?php

$connector = new ForgeConnector;

$response = $connector->send(new GetServerRequest(id: 12345));

// Create a DTO even if the response was a failure
$server = $response->dto();

// Create a DTO or throw an exception if the response is not successful
$server = $response->dtoOrFail();

Saloon will attempt to create a DTO from your response no matter the status of the response. This allows you to create "error" data transfer objects. If you don't want to use this functionality, you can use the dtoOrFail method which will throw a LogicException if the response is a failure. You can customise what is considered a failed response here.

PHPStan / TypeHinting DTOs

Due to the way DTOs are created in Saloon, you can lose the type of DTO. This can reduce the developer experience. There are two ways to get around this issue.

You can use an inline-doc block above the dto/dtoOrFail method call.

/** @var Server $server */
$server = $response->dto();

Or you can use the createDtoFromResponse method directly on your connector or request - which will use the return type specified.

$server = $request->createDtoFromResponse($response);

Using a DTO to populate request data

You may also allow your data transfer objects to go both ways, back into requests. You can do this easily with Saloon, just accept your DTO as an argument in the constructor of your request and then use the DTO to set default properties inside of the request.

Definition

<?php

use Saloon\Http\Request;
use Saloon\Enums\Method;
use Saloon\Http\Response;
use Saloon\Contracts\Body\HasBody;
use Saloon\Traits\Body\HasJsonBody;

class UpdateServerRequest extends Request implements HasBody
{
    use HasJsonBody;

    protected Method $method = Method::PUT;
    
    public function __construct(readonly protected Server $server)
    {
        //
    }
    
    public function resolveEndpoint(): string
    {
        return '/servers/' . $this->server->id;
    }
    
    protected function defaultBody(): array
    {
        return [
            'name' => $this->server->name,
        ];
    }
    
    public function createDtoFromResponse(Response $response): mixed
    {
        $data = $response->json();
    
        return new Server(
            id: $data['id'],
            name: $data['name'],
            ipAddress: $data['ip'],
        );
    }
}

Usage

Accessing the response from your DTO

Sometimes debugging a DTO can be difficult, especially if you have passed the data object through your application and no longer have access to the original Response that you created the DTO from. Saloon can inject the response into your data transfer object for you if you use the HasResponse trait and the WithResponse interface. Let's add it to our existing Server DTO.

<?php

use Saloon\Http\Response;
use Saloon\Traits\Responses\HasResponse;
use Saloon\Contracts\DataObjects\WithResponse;

class Server implements WithResponse
{
    use HasResponse;

    public function __construct(
        public readonly int $id,
        public readonly string $name,
        public readonly string $ipAddress,
    ){}
}

Now whenever we retrieve an instance of our data transfer object, you will be able to access the underlying response that was created with it!

<?php

$server = $response->dto();

$response = $server->getResponse();