343 lines
13 KiB
Racket
343 lines
13 KiB
Racket
#lang scribble/doc
|
|
@(require "web-server.rkt")
|
|
@(require (for-label web-server/servlet
|
|
xml))
|
|
|
|
@(define xexpr @tech[#:doc '(lib "xml/xml.scrbl")]{X-expression})
|
|
|
|
@title[#:tag "formlets"]{Formlets: Functional Form Abstraction}
|
|
|
|
@defmodule[web-server/formlets]
|
|
|
|
The @web-server provides a kind of Web form abstraction called a @tech{formlet}.
|
|
|
|
@margin-note{@tech{Formlet}s originate in the work of the @link["http://groups.inf.ed.ac.uk/links/"]{Links} research group in
|
|
their paper @link["http://groups.inf.ed.ac.uk/links/formlets/"]{The Essence of Form Abstraction}.}
|
|
|
|
@section{Basic Formlet Usage}
|
|
|
|
Suppose we want to create an abstraction of entering a date in an HTML form. The following
|
|
@tech{formlet} captures this idea:
|
|
|
|
@racketblock[
|
|
(define date-formlet
|
|
(formlet
|
|
(div
|
|
"Month:" ,{input-int . => . month}
|
|
"Day:" ,{input-int . => . day})
|
|
(list month day)))
|
|
]
|
|
|
|
The first part of the @racket[formlet] syntax is the template of an @xexpr that is the rendering
|
|
of the formlet. It can contain elements like @racket[,(_formlet . => . _name)] where @racket[_formlet]
|
|
is a formlet expression and @racket[_name] is an identifier bound in the second part of the @racket[formlet]
|
|
syntax.
|
|
|
|
This formlet is displayed (with @racket[formlet-display]) as the following @xexpr forest (list):
|
|
|
|
@racketblock[
|
|
(list
|
|
'(div "Month:" (input ([name "input_0"]))
|
|
"Day:" (input ([name "input_1"]))))
|
|
]
|
|
|
|
@racket[date-formlet] not only captures the rendering of the form, but also the request processing
|
|
logic. If we send it an HTTP request with bindings for @racket["input_0"] to @racket["10"] and
|
|
@racket["input_1"] to @racket["3"], with @racket[formlet-process], then it returns:
|
|
|
|
@racketblock[
|
|
(list 10 3)
|
|
]
|
|
|
|
which is the second part of the @racket[formlet] syntax, where @racket[month] has been replaced with the
|
|
integer represented by the @racket["input_0"] and @racket[day] has been replaced with the
|
|
integer represented by the @racket["input_1"].
|
|
|
|
The real power of formlet is that they can be embedded within one another. For instance, suppose we want to
|
|
combine two date forms to capture a travel itinerary. The following formlet does the job:
|
|
|
|
@racketblock[
|
|
(define travel-formlet
|
|
(formlet
|
|
(div
|
|
"Name:" ,{input-string . => . name}
|
|
(div
|
|
"Arrive:" ,{date-formlet . => . arrive}
|
|
"Depart:" ,{date-formlet . => . depart})
|
|
(list name arrive depart))))
|
|
]
|
|
|
|
(Notice that @racket[date-formlet] is embedded twice.) This is rendered as:
|
|
|
|
@racketblock[
|
|
(list
|
|
'(div
|
|
"Name:"
|
|
(input ([name "input_0"]))
|
|
(div
|
|
"Arrive:"
|
|
(div "Month:" (input ([name "input_1"]))
|
|
"Day:" (input ([name "input_2"])))
|
|
"Depart:"
|
|
(div "Month:" (input ([name "input_3"]))
|
|
"Day:" (input ([name "input_4"]))))))
|
|
]
|
|
|
|
Observe that @racket[formlet-display] has automatically generated unique names for each input element. When we pass
|
|
bindings for these names to @racket[formlet-process], the following list is returned:
|
|
|
|
@racketblock[
|
|
(list "Jay"
|
|
(list 10 3)
|
|
(list 10 6))
|
|
]
|
|
|
|
The rest of the manual gives the details of @tech{formlet} usage and extension.
|
|
|
|
@section{Syntactic Shorthand}
|
|
|
|
@(require (for-label web-server/formlets/syntax))
|
|
@defmodule[web-server/formlets/syntax]{
|
|
|
|
Most users will want to use the syntactic shorthand for creating @tech{formlet}s.
|
|
|
|
@defform[(formlet rendering yields-expr)]{
|
|
Constructs a @tech{formlet} with the specified @racket[rendering] and the processing
|
|
resulting in the @racket[yields-expr] expression. The @racket[rendering] form is a quasiquoted
|
|
@xexpr, with two special caveats:
|
|
|
|
@racket[,{_formlet-expr . => . _name}] embeds the
|
|
@tech{formlet} given by @racket[_formlet-expr]; the result of this processing this formlet is
|
|
available in the @racket[yields-expr] as @racket[_name].
|
|
|
|
@racket[,{_formlet-expr . => . (values _name ...)}] embeds the
|
|
@tech{formlet} given by @racket[_formlet-expr]; the results of this processing this formlet is
|
|
available in the @racket[yields-expr] as @racket[_name ...].
|
|
|
|
@racket[(#%# _xexpr ...)] renders an @xexpr forest.
|
|
}
|
|
|
|
@defidform[#%#]{Only allowed inside @racket[formlet].}
|
|
|
|
}
|
|
|
|
@section{Functional Usage}
|
|
|
|
@(require (for-label web-server/formlets/lib))
|
|
@defmodule[web-server/formlets/lib]{
|
|
|
|
The syntactic shorthand abbreviates the construction of @deftech{formlet}s with the following library.
|
|
These combinators may be used directly to construct low-level formlets, such as those for new INPUT element
|
|
types. Refer to @secref["input-formlets"] for example low-level formlets using these combinators.
|
|
|
|
@defthing[xexpr-forest/c contract?]{
|
|
Equivalent to @racket[(listof xexpr/c)]
|
|
}
|
|
|
|
@defproc[(formlet/c [content any/c] ...) contract?]{
|
|
Equivalent to @racket[(integer? . -> .
|
|
(values xexpr-forest/c
|
|
((listof binding?) . -> . (values (coerce-contract 'formlet/c content) ...))
|
|
integer?))].
|
|
|
|
A @tech{formlet}'s internal representation is a function from an initial input number
|
|
to an @xexpr forest rendering, a processing function, and the next allowable
|
|
input number.
|
|
}
|
|
|
|
@defthing[formlet*/c contract?]{
|
|
Equivalent to @racket[(formlet/c any/c ...)].
|
|
}
|
|
|
|
@defproc[(pure [value any/c]) (formlet/c any/c)]{
|
|
Constructs a @tech{formlet} that has no rendering and always returns @racket[value] in
|
|
the processing stage.
|
|
}
|
|
|
|
@defproc[(cross [f (formlet/c procedure?)]
|
|
[g (formlet/c any/c ...)])
|
|
(formlet/c any/c ...)]{
|
|
Constructs a @tech{formlet} with a rendering equal to the concatenation of the renderings of @tech{formlet}s @racket[f] and @racket[g];
|
|
a processing stage that applies @racket[g]'s processing results to @racket[f]'s processing result.
|
|
}
|
|
|
|
@defproc[(cross* [f (formlet/c (() () #:rest (listof any/c) . ->* . any/c))]
|
|
[g (formlet/c any/c)] ...)
|
|
(formlet/c any/c)]{
|
|
Equivalent to @racket[cross] lifted to many arguments.
|
|
}
|
|
|
|
@defproc[(xml-forest [r xexpr-forest/c])
|
|
(formlet/c procedure?)]{
|
|
Constructs a @tech{formlet} with the rendering @racket[r] and the identity procedure as the processing step.
|
|
}
|
|
|
|
@defproc[(xml [r xexpr/c])
|
|
(formlet/c procedure?)]{
|
|
Equivalent to @racket[(xml-forest (list r))].
|
|
}
|
|
|
|
@defproc[(text [r string?])
|
|
(formlet/c procedure?)]{
|
|
Equivalent to @racket[(xml r)].
|
|
}
|
|
|
|
@defproc[(tag-xexpr [tag symbol?]
|
|
[attrs (listof (list/c symbol? string?))]
|
|
[inner (formlet/c any/c)])
|
|
(formlet/c any/c)]{
|
|
Constructs a @tech{formlet} with the rendering @racket[(list (list* tag attrs inner-rendering))] where @racket[inner-rendering] is
|
|
the rendering of @racket[inner] and the processing stage identical to @racket[inner].
|
|
}
|
|
|
|
@defproc[(formlet-display [f (formlet/c any/c)])
|
|
xexpr-forest/c]{
|
|
Renders @racket[f].
|
|
}
|
|
|
|
@defproc[(formlet-process [f (formlet/c any/c ...)]
|
|
[r request?])
|
|
(values any/c ...)]{
|
|
Runs the processing stage of @racket[f] on the bindings in @racket[r].
|
|
}
|
|
|
|
}
|
|
|
|
@section[#:tag "input-formlets"]{Predefined Formlets}
|
|
|
|
@(require (for-label web-server/formlets/input))
|
|
@defmodule[web-server/formlets/input]{
|
|
|
|
These @tech{formlet}s are the main combinators for form input.
|
|
|
|
@defproc[(make-input [render (string? . -> . xexpr/c)])
|
|
(formlet/c (or/c false/c binding?))]{
|
|
This @tech{formlet} is rendered with @racket[render], which is passed the input name, and results in the
|
|
extracted @racket[binding].
|
|
}
|
|
|
|
@defproc[(make-input* [render (string? . -> . xexpr/c)])
|
|
(formlet/c (listof binding?))]{
|
|
This @tech{formlet} is rendered with @racket[render], which is passed the input name, and results in all the
|
|
@racket[binding]s that use the name.
|
|
}
|
|
|
|
@defproc[(text-input [#:value value (or/c false/c bytes?) #f]
|
|
[#:size size (or/c false/c exact-nonnegative-integer?) #f]
|
|
[#:max-length max-length (or/c false/c exact-nonnegative-integer?) #f]
|
|
[#:read-only? read-only? boolean? #f]
|
|
[#:attributes attrs (listof (list/c symbol? string?)) empty])
|
|
(formlet/c (or/c false/c binding?))]{
|
|
This @tech{formlet} renders using an INPUT element with the TEXT type and the attributes given in the arguments.
|
|
}
|
|
|
|
@defproc[(password-input [#:value value (or/c false/c bytes?) #f]
|
|
[#:size size (or/c false/c exact-nonnegative-integer?) #f]
|
|
[#:max-length max-length (or/c false/c exact-nonnegative-integer?) #f]
|
|
[#:read-only? read-only? boolean? #f]
|
|
[#:attributes attrs (listof (list/c symbol? string?)) empty])
|
|
(formlet/c (or/c false/c binding?))]{
|
|
This @tech{formlet} renders using an INPUT element with the PASSWORD type and the attributes given in the arguments.
|
|
}
|
|
|
|
@defproc[(textarea-input)
|
|
(formlet/c string?)]{
|
|
This @tech{formlet} renders using an TEXTAREA element.
|
|
}
|
|
|
|
@defproc[(checkbox [value bytes?]
|
|
[checked? boolean?]
|
|
[#:attributes attrs (listof (list/c symbol? string?)) empty])
|
|
(formlet/c (or/c false/c binding?))]{
|
|
This @tech{formlet} renders using a INPUT elemen with the CHECKBOX type and the attributes given in the arguments.
|
|
}
|
|
|
|
@defproc[(multiselect-input [l sequence?]
|
|
[#:multiple? multiple? boolean? #t]
|
|
[#:selected? selected? (any/c . -> . boolean?) (λ (x) #f)]
|
|
[#:display display (any/c . -> . xexpr/c) (λ (x) x)])
|
|
(formlet/c list?)]{
|
|
This @tech{formlet} renders using an SELECT element with an OPTION for each element of the sequence. If @racket[multiple?] is @racket[#t], then multiple options may be selected. An element is selected if @racket[selected?] returns @racket[#t]. Elements are displayed with @racket[display].
|
|
}
|
|
|
|
@defproc[(select-input [l sequence?]
|
|
[#:selected? selected? (any/c . -> . boolean?) (λ (x) #f)]
|
|
[#:display display (any/c . -> . xexpr/c) (λ (x) x)])
|
|
(formlet/c any/c)]{
|
|
This @tech{formlet} renders using an SELECT element with an OPTION for each element of the sequence. An element is selected if @racket[selected?] returns @racket[#t]. Elements are displayed with @racket[display].
|
|
}
|
|
|
|
@defproc[(required [f (formlet/c (or/c false/c binding?))])
|
|
(formlet/c bytes?)]{
|
|
Constructs a @tech{formlet} that extracts the @racket[binding:form-value] from the binding produced by @racket[f], or errors.
|
|
}
|
|
|
|
@defproc[(default
|
|
[def bytes?]
|
|
[f (formlet/c (or/c false/c binding?))])
|
|
(formlet/c bytes?)]{
|
|
Constructs a @tech{formlet} that extracts the @racket[binding:form-value] from the binding produced by @racket[f], or returns @racket[def].
|
|
}
|
|
|
|
@defproc[(to-string [f (formlet/c bytes?)])
|
|
(formlet/c string?)]{
|
|
Converts @racket[f]'s output to a string. Equivalent to @racket[(cross (pure bytes->string/utf-8) f)].
|
|
}
|
|
|
|
@defproc[(to-number [f (formlet/c string?)])
|
|
(formlet/c number?)]{
|
|
Converts @racket[f]'s output to a number. Equivalent to @racket[(cross (pure string->number) f)].
|
|
}
|
|
|
|
@defproc[(to-symbol [f (formlet/c string?)])
|
|
(formlet/c symbol?)]{
|
|
Converts @racket[f]'s output to a symbol. Equivalent to @racket[(cross (pure string->symbol) f)].
|
|
}
|
|
|
|
@defproc[(to-boolean [f (formlet/c bytes?)])
|
|
(formlet/c boolean?)]{
|
|
Converts @racket[f]'s output to a boolean, if it is equal to @racket[#"on"].
|
|
}
|
|
|
|
@defthing[input-string (formlet/c string?)]{
|
|
Equivalent to @racket[(to-string (required (text-input)))].
|
|
}
|
|
|
|
@defthing[input-int (formlet/c integer?)]{
|
|
Equivalent to @racket[(to-number input-string)].
|
|
}
|
|
|
|
@defthing[input-symbol (formlet/c symbol?)]{
|
|
Equivalent to @racket[(to-symbol input-string)].
|
|
}
|
|
|
|
}
|
|
|
|
@section{Utilities}
|
|
|
|
@(require (for-label web-server/formlets/servlet))
|
|
@defmodule[web-server/formlets/servlet]{
|
|
|
|
A few utilities are provided for using @tech{formlet}s in Web applications.
|
|
|
|
@defproc[(send/formlet [f (formlet/c any/c ...)]
|
|
[#:wrap wrapper
|
|
(xexpr/c . -> . response/c)
|
|
(lambda (form-xexpr)
|
|
`(html (head (title "Form Entry"))
|
|
(body ,form-xexpr)))])
|
|
(values any/c ...)]{
|
|
Uses @racket[send/suspend] to send @racket[f]'s rendering (wrapped in a FORM tag whose action is
|
|
the continuation URL (wrapped again by @racket[wrapper])) to the client.
|
|
When the form is submitted, the request is passed to the
|
|
processing stage of @racket[f].
|
|
}
|
|
|
|
@defproc[(embed-formlet [embed/url embed/url/c]
|
|
[f (formlet/c any/c ...)])
|
|
xexpr/c]{
|
|
Like @racket[send/formlet], but for use with @racket[send/suspend/dispatch].
|
|
}
|
|
|
|
}
|