2.4.2 Bindings

(require web-server/http/bindings)

These functions, while convenient, could introduce subtle bugs into your application. Examples: that they are case-insensitive could introduce a bug; if the data submitted is not in UTF-8 format, then the conversion to a string will fail; if an attacker submits a form field as if it were a file, when it is not, then the request-bindings will hold a bytes? object and your program will error; and, for file uploads you lose the filename. Therefore, we recommend against their use, but they are provided for compatibility with old code.

(request-bindings req)

→   (listof (or/c (cons/c symbol? string?)               (cons/c symbol? bytes?)))

req : request?

Translates the request-bindings/raw of req by interpreting bytes? as string?s, except in the case of binding:file bindings, which are left as is. Ids are then translated into lowercase symbols.

(request-headers req) → (listof (cons/c symbol? string?))

req : request?

Translates the request-headers/raw of req by interpreting bytes? as string?s. Ids are then translated into lowercase symbols.

(extract-binding/single id binds) → string?

id : symbol?

binds : (listof (cons/c symbol? string?))

Returns the single binding associated with id in the a-list binds if there is exactly one binding. Otherwise raises exn:fail.

(extract-bindings id binds) → (listof string?)

id : symbol?

binds : (listof (cons/c symbol? string?))

Returns a list of all the bindings of id in the a-list binds.

(exists-binding? id binds) → boolean?

id : symbol?

binds : (listof (cons/c symbol? string))

Returns #t if binds contains a binding for id. Otherwise, #f.

Here is an example typical of what you will find in many applications:

(define (get-number req)

(string->number

(extract-binding/single

'number

(request-bindings req))))