Generating a Response

To generate a response a class should implement the GeneratesResponseInterface interface and define the 'generateResponse()' method.

UrlHandler objects implement this interface however they usually instantiate a specialist class that generates the real response.

The class should return a Response object, normally a HtmlResponse for web requests or a JsonResponse for a REST API.

A simple response generator might look like this:

class GreetingResponder implements GeneratesResponseInterface
{
    public function generateResponse(Request $request)
    {
        $response = new HtmlResponse();
        $response->setContent("<p>Welcome friend!</p>");

        return $response;
    }
}

To connect this with a URL you can use the ClassMappedUrlHandler. For example here we configure it to serve the homepage of our site:

// In registerUrlHandlers of your module class:
$this->addUrlHandlers(
[
    "/" => new ClassMappedUrlHandler(GreetingResponser::class)
]);

Creating HTML directly in a response generating object is something usually reserved for very simple, non interactive use cases. For normal interactive screen design it's better to use a design pattern like MVP which you can find in the leaf module.