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Small bug in tutorial

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svn: r15800
This commit is contained in:
Jay McCarthy 2009-08-26 15:00:01 +00:00
parent 7bc34a406e
commit e49bd5d60a
1 changed files with 12 additions and 12 deletions
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24
collects/web-server/scribblings/tutorial/continue.scrbl
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@ -341,19 +341,19 @@ web-server/insta
@code:comment{phase-1: request -> html-response} @code:comment{phase-1: request -> html-response}
(define (phase-1 request) (define (phase-1 request)
(local [(define (response-generator make-url) (local [(define (response-generator embed/url)
`(html `(html
(body (h1 "Phase 1") (body (h1 "Phase 1")
(a ((href ,(make-url phase-2))) (a ((href ,(embed/url phase-2)))
"click me!"))))] "click me!"))))]
(send/suspend/dispatch response-generator))) (send/suspend/dispatch response-generator)))
@code:comment{phase-2: request -> html-response} @code:comment{phase-2: request -> html-response}
(define (phase-2 request) (define (phase-2 request)
(local [(define (response-generator make-url) (local [(define (response-generator embed/url)
`(html `(html
(body (h1 "Phase 2") (body (h1 "Phase 2")
(a ((href ,(make-url phase-1))) (a ((href ,(embed/url phase-1)))
"click me!"))))] "click me!"))))]
(send/suspend/dispatch response-generator))) (send/suspend/dispatch response-generator)))
] ]
@ -366,15 +366,15 @@ cycle repeats.
Let's look more closely at the @scheme[send/suspend/dispatch] mechanism. Let's look more closely at the @scheme[send/suspend/dispatch] mechanism.
@scheme[send/suspend/dispatch] consumes a response-generating function, and it @scheme[send/suspend/dispatch] consumes a response-generating function, and it
gives that response-generator a function called @scheme[make-url] that we'll gives that response-generator a function called @scheme[embed/url] that we'll
use to build special URLs. What makes these URLs special is this: use to build special URLs. What makes these URLs special is this:
when a web browser visits these URLs, our web application restarts, when a web browser visits these URLs, our web application restarts,
but not from start, but from the handler that we associate to the URL. but not from start, but from the handler that we associate to the URL.
In @scheme[phase-1], the use of @scheme[make-url] associates the link with @scheme[phase-2], and In @scheme[phase-1], the use of @scheme[embed/url] associates the link with @scheme[phase-2], and
vice versa. vice versa.
We can be more sophisticated about the handlers associated with We can be more sophisticated about the handlers associated with
@scheme[make-url]. Because the handler is just a request-consuming function, @scheme[embed/url]. Because the handler is just a request-consuming function,
it can be defined within a @scheme[local]. Consequently, a local-defined it can be defined within a @scheme[local]. Consequently, a local-defined
handler knows about all the variables that are in the scope of its handler knows about all the variables that are in the scope of its
definition. Here's another loopy example: definition. Here's another loopy example:
@ -389,10 +389,10 @@ web-server/insta
@code:comment{Displays a number that's hyperlinked: when the link is pressed,} @code:comment{Displays a number that's hyperlinked: when the link is pressed,}
@code:comment{returns a new page with the incremented number.} @code:comment{returns a new page with the incremented number.}
(define (show-counter n request) (define (show-counter n request)
(local [(define (response-generator make-url) (local [(define (response-generator embed/url)
`(html (head (title "Counting example")) `(html (head (title "Counting example"))
(body (body
(a ((href ,(make-url next-number-handler))) (a ((href ,(embed/url next-number-handler)))
,(number->string n))))) ,(number->string n)))))
(define (next-number-handler request) (define (next-number-handler request)
@ -542,13 +542,13 @@ should let us add comments.
Each point in the diagram corresponds to a request-consuming handler. Each point in the diagram corresponds to a request-consuming handler.
As we might suspect, we'll be using @scheme[send/suspend/dispatch] some more. As we might suspect, we'll be using @scheme[send/suspend/dispatch] some more.
Every arrow in the diagram will be realized as a URL that we generate Every arrow in the diagram will be realized as a URL that we generate
with @scheme[make-url]. with @scheme[embed/url].
This has a slightly messy consequence: previously, we've been This has a slightly messy consequence: previously, we've been
rendering the list of posts without any hyperlinks. But since any rendering the list of posts without any hyperlinks. But since any
function that generates a special dispatching URL uses make-url to do function that generates a special dispatching URL uses @scheme[embed/url] to do
it, we'll need to adjust @scheme[render-posts] and @scheme[render-post] to consume and it, we'll need to adjust @scheme[render-posts] and @scheme[render-post] to consume and
use @scheme[make-url] itself when it makes those hyperlinked titles. use @scheme[embed/url] itself when it makes those hyperlinked titles.
Our web application now looks like: Our web application now looks like: