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Body

The HTTP.Body represents the payload of an HTTP.Message, and is used to pass the underlying data. Some examples of this in practice would be JSON, HTML text, or the bytes of an image. Let's look at the implementation:

public enum Body {
    case data(Bytes)
    case chunked((ChunkStream) throws -> Void)
}

Data Case

The data case is by far the most common use for a Body in an HTTP.Message. It is simply an array of bytes. The serialization protocol or type associated with these bytes is usually defined by the Content-Type header. Let's look at some examples.

Application/JSON

If our Content-Type header contains application/json, then the underlying bytes represent serialized JSON.

if let contentType = req.headers["Content-Type"], contentType.contains("application/json"), let bytes = req.body.bytes {
  let json = try JSON(bytes: bytes)
  print("Got JSON: \(json)")
}

Image/PNG

If our Content-Type contains image/png, then the underlying bytes represent an encoded png.

if let contentType = req.headers["Content-Type"], contentType.contains("image/png"), let bytes = req.body.bytes {
  try database.save(image: bytes)
}

Chunked Case

The chunked case only applies to outgoing HTTP.Messages in Vapor. It is traditionally a responder's role to collect an entire chunked encoding before passing it on. We can use this to send a body asynchronously.

let body: Body = Body.chunked(sender)
return Response(status: .ok, body: body)

We can implement this manually, or use Vapor's built in convenience initializer for chunked bodies:

return Response(status: .ok) { chunker in
  for name in ["joe", "pam", "cheryl"] {
      sleep(1)
      try chunker.send(name)
  }

  try chunker.close()
}

Make sure to call close() before the chunker leaves scope.

BodyRepresentable

In addition to the concrete Body type, as is common in Vapor, we also have wide support for BodyRepresentable. This means objects that we're commonly converting to Body type can be used interchangeably. For example:

return Response(body: "Hello, World!")

In the above example, string is converted to bytes and added to the body.

In practice, it is better to use return "Hello, World!". Vapor will automatically be able to set the Content-Type to appropriate values.

Let's look at how it's implemented:

public protocol BodyRepresentable {
    func makeBody() -> Body
}

Custom

We can conform our own types to this as well where applicable. Let's pretend we have a custom data type, .vpr. Let's conform our VPR file type model:

extension VPRFile: HTTP.BodyRepresentable {
  func makeBody() -> Body {
    // collect bytes
    return .data(bytes)
  }
}

You may have noticed above, that the protocol throws, but our implementation does not. This is completely valid in Swift and will allow you to not throw if you're ever calling the function manually.

Now we're able to include our VPR file directly in our Responses.

drop.get("files", ":file-name") { request in
  let filename = try request.parameters.extract("file-name") as String
  let file = VPRFileManager.fetch(filename)
  return Response(status: .ok, headers: ["Content-Type": "file/vpr"], body: file)
}

In practice, if we're repeating this often, we'll probably conform VPRFile directly to ResponseRepresentable

extension VPRFile: HTTP.ResponseRepresentable {
  func makeResponse() -> Response {
    return Response(
      status: .ok,
      headers: ["Content-Type": "file/vpr"],
      body: file
    )
  }
}

Here's our above example now:

drop.get("files", ":file-name") { request in
  let filename = try request.parameters.extract("file-name") as String
  return VPRFileManager.fetch(filename)
}

We could also use type-safe routing to make this even more concise:

drop.get("files", String.self) { request, filename in
  return VPRFileManager.fetch(filename)
}