suzanne.soy/racket
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

Small bug in tutorial

Browse Source 
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
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

24
collects/web-server/scribblings/tutorial/continue.scrbl
View File

@ -341,19 +341,19 @@ web-server/insta
@code:comment{phase-1: request -> html-response}
(define (phase-1 request)
(local [(define (response-generator make-url)
(local [(define (response-generator embed/url)
`(html
(body (h1 "Phase 1")
(a ((href ,(make-url phase-2)))
(a ((href ,(embed/url phase-2)))
"click me!"))))]
(send/suspend/dispatch response-generator)))
@code:comment{phase-2: request -> html-response}
(define (phase-2 request)
(local [(define (response-generator make-url)
(local [(define (response-generator embed/url)
`(html
(body (h1 "Phase 2")
(a ((href ,(make-url phase-1)))
(a ((href ,(embed/url phase-1)))
"click me!"))))]
(send/suspend/dispatch response-generator)))
]
@ -366,15 +366,15 @@ cycle repeats.
Let's look more closely at the @scheme[send/suspend/dispatch] mechanism.
@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:
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.
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.
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
handler knows about all the variables that are in the scope of its
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{returns a new page with the incremented number.}
(define (show-counter n request)
(local [(define (response-generator make-url)
(local [(define (response-generator embed/url)
`(html (head (title "Counting example"))
(body
(a ((href ,(make-url next-number-handler)))
(a ((href ,(embed/url next-number-handler)))
,(number->string n)))))
(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.
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
with @scheme[make-url].
with @scheme[embed/url].
This has a slightly messy consequence: previously, we've been
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
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: