.. _request_type:

The type of request definitions
===============================

All request definitions have type ``RequestT[U, T, S]`` (RequestT as in Request Template). If this looks a bit complex, don't worry, what the three type parameters stand for is the only thing you'll hopefully have to remember when using the API!

Going one-by-one:

* ``U[_]`` specifies if the request method and URL are specified. Using the API, this can be either ``type Empty[X] = None``, meaning that the request has neither a method nor an URI. Or, it can be ``type Id[X] = X`` (type-level identity), meaning that the request has both a method and an URI specified. Only requests with a specified URI & method can be sent.
* ``T`` specifies the type to which the response will be read. By default, this is ``String``. But it can also be e.g. ``Array[Byte]`` or ``Unit``, if the response should be ignored. Response body handling can be changed by calling the ``.response`` method. With backends which support streaming, this can also be a supported stream type. See :ref:`response body specifications <responsebodyspec>` for more details.
* ``S`` specifies the stream type that this request uses. Most of the time this will be ``Nothing``, meaning that this request does not send a streaming body or receive a streaming response. So most of the time you can just ignore that parameter. But, if you are using a streaming backend and want to send/receive a stream, the ``.streamBody`` or ``response(asStream[S])`` will change the type parameter. 

There are two type aliases for the request template that are used:

* ``type Request[T, S] = RequestT[Id, T, S]``. A sendable request.
* ``type PartialRequest[T, S] = RequestT[Empty, T, S]``

As ``sttp``, the starting request, by default reads the body into a ``String``, its type is::

  sttp: PartialRequest[String, Nothing]