@@ -60,8 +60,8 @@ ;; (define-syntax body-as-url (syntax-rules () - ((_ (identifiers ...) body ...) - (closure-key->url (body-as-closure-key (identifiers ...) body ...))))) + ((_ (spec ...) body ...) + (closure-key->url (body-as-closure-key (spec ...) body ...))))) (define (closure-key->url clos-key) (format "~A?~A=~A" closures.scm @@ -167,6 +167,26 @@ When you define a session page, the session is automatically fetched for you (an @defproc[(session-put-val! (session session) (key symbol) (val any)) session] +@subsection{Storing closures in URLs} + +LeftParen provides a simple way to create closures and attach them to a URL. Using this technique is often much simpler than the more traditional encoding of values in a URL by hand. + +@defform[ +#:id body-as-url +(body-as-url (req-iden [key] [#:sticky]) body ...) +]{Creates a URL which, when visited, will execute the given @scheme[body]. If @scheme[key] is provided, then it will be used as the id to represent the closure. It's more common, however, to not pass your own key--in which case, a unique, random one will be chosen for you. @scheme[req-iden] will be bound to the request created when the link is executed and available for use in @scheme[body]. If @scheme[#:sticky] is provided, then the closure will be available for execution until the server is stopped. Otherwise, it is available for execution just once. + +@schemeblock[ +(define-page (index-page req) + (let ((x 0)) + (web-link "Click to increment" + (body-as-url (req) + (set! x (+ x 1)) + (format "x is ~A" x))))) +] + +This creates a link, which, when clicked, prints @tt{x is 1}. If you reload the page, however, you'll see something like @tt{Expired or missing function 'q7c5ysd4935xhbhx2xbu'}. Changing the first sub-form passed to @scheme[body-as-url] to @scheme[(req #:sticky)] makes it so that successive hits to the link result in increasing values of @scheme[x]. +} @subsection{Users} scribblings/leftparen.scrbl 2a332f6de9b79d49d62de16e9e3033cf72638f7a Rob Hunter rob.hunter@gmail.com http://github.com/vegashacker/leftparen/commit/126f8489442bc52f3c990c913813a021fb6d9920 126f8489442bc52f3c990c913813a021fb6d9920 2009-05-15T11:53:46-07:00 2009-05-15T11:53:46-07:00 added some documentation on body-as-url c7b50d9182a249aef59c9d9c96987e760beaf84b Rob Hunter rob.hunter@gmail.com