Spin

Write RESTful web apps in Racket.

Spin layers some convenience functions on top of Racket's built-in web server to simplify defining routes and route handlers.

Overview

Define routes with one of get, post, put, patch, delete and pass it the route string and a handler function.

#lang racket

(require (planet dmac/spin))

(get "/"
  (lambda () "Hello!"))

(run)

Your handler function will be passed the request object if an argument is specified.

It can be given to the params function along with a key to search for values in the query-string, post-body, or url.

(get "/hi" (lambda (req)
  (string-append "Hello, " (params req 'name) "!")))

$ curl "http://localhost:8000/hi?name=Charlotte"
Hello, Charlotte!

$ curl "http://localhost:8000/hi" -X POST -d "name=Anansi"
Hello, Anansi!

Retrieve params from the url string itself:

(get "/hi/:name" (lambda (req)
  (string-append "Hello, " (params req 'name) "!")))

$ curl "http://localhost:8000/hi/Peter"
Hello, Peter!

Your handler function need only return a string to render. You can easily use existing templating libraries with Spin.

app.rkt

(require web-server/templates)

(get "/template" (lambda (req)
  (define name (params req 'name))
  (include-template "index.html")))

(run)

index.html

<html>
  <body>
    <p>Hello, @|name|!</p>
  </body>
</html>

$ curl "http://localhost:8000/template?name=Aragog"
<html>
  <body>
    <p>Hello, Aragog!</p>
  </body>
</html>

In addition to the response body, you can specify response status and custom headers if you return a list instead of a string from your handler:

(get "/headers" (lambda ()
  (define h (header #"Custom-Header" #"Itsy bitsy"))
  `(201 (,h) "Look for the custom header!")))