Note: This is taken from the Chicken Wiki, where a more recent version could be available.


The sxml-templates egg uses sxml-transforms to perform variable substitution on SXML expressions. It defines a record type which represents a SXML template, and includes some procedures for substituting values into that template. The general idea is to enable the use of on-disk files containing only SXML expressions which are loaded and substituted-into as necessary, as opposed to defining procedures which return quasiquoted SXML.


sxml-templates is in the Public Domain and may be reproduced or copied without permission.


Moe Aboulkheir



Uselessly simple example

(use sxml-templates)

(printf "~A\n" (sxml-template:fill-string
                 (make-sxml-template '(%data key))
                 '((key . "value"))))

Will print the string value.

Using with Spiffy

(use sxml-templates spiffy)

(define (my-app:read-sxml-template basename)
    (read (open-input-file (string-append "templates/" basename ".scm")))))

  (lambda (req args)
    (let* ((login-form-template
             (my-app:read-sxml-template "login-form-body"))
             '((form-method . "POST")
               (form-action . "/login-form-post-target")
               (username-input-name . "username")
               (password-input-name . "password")))
             (sxml-templates:fill login-form-template login-form-namespace)))
      ; write some response headers, etc
          (my-app:read-sxml-template "shell")
          `((body . ,login-form-template)))))))

templates/shell.scm would look something like:

  (head (title "My Application"))
  (body (%data body)))

templates/login-form-body.scm would look something like:

 (@ (method (%data form-method))
    (action (%data form-action)))
 (label "Username")
 (input (@ (type "text")
           (name (%data username-input-name))))
 (label "Password")
 (input (@ (type "password")
           (name (%data password-input-name))))
 (input (@ (type "submit"))))

The resource handler in the example first subtitutes some variables into the login-form-body template, and then substitutes the result into the shell template.



[procedure] (make-sxml-template sxml)

Where sxml is an SXML expression. Returns a sxml-template record.


[procedure] (sxml-template:fill sxml-template namespace)

Where sxml-template is a sxml-template record and namespace is an association list mapping variable names to values. This will replace all instances of (%data name) in sxml-template's underlying SXML with the result of (alist-ref 'name alist), and return a new sxml-template record. If a value in namespace is a filled sxml-template, then the right thing will happen. If a value is a list, then it is assumed to be vanilla SXML and will be converted using SXML's universal-conversion-rules. If a value is mentioned in the template's SXML which does not have a corresponding entry in the alist, then an error will be signalled. See sxml-template:fill-string for an equivalent which results in a string of XML, and sxml-template->string for a procedure which will convert a filled sxml-template record (as returned by this procedure) to a string of XML.



 [procedure] (sxml-template? x)

Returns a boolean indicating whether x is of the sxml-template record type.


[procedure] (sxml-template:filled? sxml-template)

Returns a boolean indicating whether sxml-template has been filled (see sxml-template:fill).



[procedure] (sxml-template:sxml sxml-template)

Returns the value of the sxml argument in the make-sxml-template call which was used to construct the given sxml-template.



[procedure] (sxml-template:fill-string sxml-template namespace)

Similar to sxml-template:fill, but results in an XML string. Defined as (compose sxml-template->string sxml-template:fill).


[procedure] (sxml-template->string sxml-template)

Converts a filled sxml-template record (as returned by sxml-template:fill) into an XML string.