Responder Guide

Responder is Mocket’s unified response protocol. Route handlers and middlewares return an object that implements Responder. The runtime uses it to populate HttpResponse headers and status, and to serialize the body.

Responder Trait

trait Responder {
  options(Self, res: HttpResponse) -> Unit
  output(Self, buf: @buffer.Buffer) -> Unit
}

Common constructs:

• Text: return String / StringView.
• JSON: return Json or an object’s .to_json(); or HttpResponse::json(...).
• Binary: return Bytes.
• HTML: use html(showable).
• Full response: return HttpResponse::new(...), or use .to_responder() when you need an explicit responder object.

Custom Responder

Implement Responder for your own type to control headers and serialization, e.g., CSV:

struct Csv(String)

impl @mocket.Responder for Csv with options(_, res) -> Unit {
  res.headers["Content-Type"] = "text/csv; charset=utf-8"
}

impl @mocket.Responder for Csv with output(self, buf) -> Unit {
  buf.write_bytes(@utf8.encode(self.0))
}

@mocket.HttpResponse::new(OK).body(Csv("a,b,c\n1,2,3"))

Usage Example

// Text Response
app.get("/", _event => "⚡️ Tadaa!")

// JSON Request
// curl --location 'localhost:4000/json' \
// --header 'Content-Type: application/json' \
// --data '{
//     "name": "oboard",
//     "age": 21
// }'
app.post("/json", event => {
  try {
    let payload : Json = event.req.json()
    guard payload is Object(obj) else {
      return HttpResponse::new(BadRequest).body("Invalid JSON")
    }
    guard obj.get("name") is Some(String(name)) else {
      return HttpResponse::new(BadRequest).body("Invalid JSON")
    }
    guard obj.get("age") is Some(Number(age, ..)) else {
      return HttpResponse::new(BadRequest).body("Invalid JSON")
    }
    "Hello, \{name}. You are \{age.to_int()} years old."
  } catch {
    _ => return HttpResponse::new(BadRequest).body("Invalid JSON")
  }
})

// Echo Server
app.post("/echo", e => e.req)

// HTML Response
app.get("/html", _ => {
  HttpResponse::new(OK).body(@mocket.html("<h1>Hello</h1>"))
})