(app ["hi"] {:get "Hello World!"})
Moustache is a micro web framework/internal DSL to wire Ring handlers and middlewares.
Well, there’s only one macro you need to know: app.
Every other public var is public only because app needs it in its expansion.
See syntax.html
A (app ...) form returns a Ring application (handler).
There’s currently four usages of app:
- to wrap a Ring handler,
- to define routes,
- to dispatch on HTTP methods
- and to render plain text.
(app my-handler) ; identity, returns my-handler
You can simply wrap a handler into middlewares:
(app
middleware1
(middleware2 arg)
my-handler)
; equivalent to (→ my-handler (middleware2 arg) middleware1)
; ie (middleware1 (middleware2 my-handler arg))
Note that every usage of app supports middleware-wrapping.
With Moustache you don’t write routes as encoded uri (eg "/Thank%20you%20Mario/But%20our%20princess%20is%20in%20another%20castle"), you write vectors of decoded segments (eg ["Thank you Mario" "But our princess is in another castle"]).
(app ["foo"] my-handler) ; will route requests to "/foo" to my-handler (app ["foo" ""] my-handler) ; will route requests to "/foo/" to my-handler (app ["foo" "bar"] my-handler) ; will route requests to "/foo/bar" to my-handler (app ["foo" &] my-handler) ; will route requests to "/foo", "/foo/", "/foo/bar" and "/foo/bar/baz/" to my-handler (and will chop "/foo" off from the uri) (app ["foo" name] my-handler) ; will route requests to "/foo/", "/foo/bar" to my-handler and bind @name@ (a local) to the matched segment (eg "" or "bar") (app ["foo" x & xs] my-handler) ; "/foo/bar/baz/bloom" will bind x to bar and xs to ["baz" "bloom"]
You can catch all URIs with the route [&]. If you don’t provide a handler for [&] and there’s no handler for a request Moustache sends a 404 (not found) response.
(defn integer [s]
"returns nil if s does not represent an integer
(try
(Integer/parseInt s)
(catch Exception e)))
(app ["order" [id integer]] my-handler) ; for "/order/134" @id@ will be bind to 134 (not "134"), this route will not match "/order/abc".
(app ["agenda" [[_ year month day] #"(\d{4})-(\d{2})-(\d{2})"]]
{:get [month "-" day "-" year " agenda"]})
The routes are tried in order until one route matches the request uri and the associated handler does not return nil.
That’s why:
(app ["foo" &] (app ["bar"] handler1) ["foo" "baz"] handler2)
returns a 404 for /foo/baz: the nested app form returns a 404 for /baz and this 404 bubbles up.
You can prevent such behavior by writing:
(app ["foo" &] (app ["bar"] handler1 [&] pass) ["foo" "baz"] handler2)
(app :get handler-for-get :post handler-for-post)
You can add a catch-all using the :any keyword.
If you don’t specify a handler for :any, Moustache sends a 405 response (method not allowed).
When the right-hand form of a route or of a method dispatch is a (app ...) form, you can write the form as a vector: (app ["foo" &] (app ["bar"] handler)) can be shortened to (app ["foo" &] [["bar"] handler]).
Besides when the right-hand form is a method dispatch without middlewares you can write the form as a map: (app ["foo"] (app :get handler)) can be shortened to (app ["foo"] {:get handler}).