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 response body specifications 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]