继我的解决方案之后，将第 4 章中的代码用作 here , 我需要一些帮助调试 lisp webtales 第 5 章中的应用程序“linkdemo” .
我已经仔细输入了所有代码并消除了书中包含的一个错字。
在 CCL如果我发出 (ql:quickload "linkdemo")我明白了:
CCL is free software. It is distributed under the terms of the Apache
Licence, Version 2.0.
? (ql:quickload "linkdemo")
To load "linkdemo":
Load 1 ASDF system:
linkdemo
; Loading "linkdemo"
.
;;; Checking for wide character support... yes, using code points.
;;; Checking for wide character support... yes, using code points.
;;; Building Closure with CHARACTER RUNES
.
> Error: The value NIL is not of the expected type STRING.
> While executing: ENSURE-SIMPLE-STRING, in process listener(1).
> Type :POP to abort, :R for a list of available restarts.
> Type :? for other options.
1 >
如果我输入
:R我明白了:1 > :R
> Type (:C <n>) to invoke one of the following restarts:
0. Return to break level 1.
1. #<RESTART ABORT-BREAK #x133AEDD>
2. Retry compiling #P"/Users/m/quicklisp/local-projects/linkdemo/defmodule.lisp"
3. Skip compiling #P"/Users/m/quicklisp/local-projects/linkdemo/defmodule.lisp"
4. Retry compiling #<CL-SOURCE-FILE "linkdemo" "defmodule">.
5. Continue, treating compiling #<CL-SOURCE-FILE "linkdemo" "defmodule"> as having been successful.
6. Retry ASDF operation.
7. Retry ASDF operation after resetting the configuration.
8. Give up on "linkdemo"
9. Return to toplevel.
10. #<RESTART ABORT-BREAK #x133C53D>
11. Reset this thread
12. Kill this thread
1 >
我从中推断出错误在
defmodule.lisp .然后，我发现如果我注释掉
defmodule.lisp 中的以下整个 block :(restas:define-policy datastore
(:interface-package #:linkdemo.policy.datastore)
(:interface-method-template "DATASTORE-~A")
(:internal-package #:linkdemo.datastore)
(define-method init ()
"Initiate the datastore")
(define-method find-user (username)
"Find the user by username")
(define-method auth-user (username password)
"Check if a user exists and has the supplied password")
(define-method register-user (username password)
"Register a new user")
(define-method upvoted-p (link-id username)
"Check if a user has upvoted a link")
(define-method upvote (link-id user)
"Upvote a link")
(define-method post-link (url title user)
"Post a new link")
(define-method get-all-links (&optional user)
"Get all of the links in the datastore")
(define-method upvote-count (link-id)
"Get the number of upvotes for a given link"))
然后重新发布
(ql:quickload "linkdemo") ，我没有错误。(另外，如果我再次评论它，并使用快速加载重新加载，我也没有收到错误。我不确定那里发生了什么或原因。)
无论我是否快速加载了上面有问题的部分，我都可以在
pg-datastore.lisp 中探索一个功能。 ，像这样:1 > (linkdemo.pg-datastore::hash-password "42")
(:PASSWORD-HASH "71a8c8f54475acb5afee9eae061fa5f7ba838215f280259855e59a7c0ac768f8" :SALT "a283c5328f67c36595dd7277c54342f3")
似乎还不能尝试启动服务器，因为需要第 6 章中的代码才能完全发挥作用(我们还没有路由，只有带有
postmodern 的 DAO 层)。所以不知道如何继续测试第 5 章中的代码/调试这个。
该错误似乎是restas本身的东西-也许。
寻求有关如何进行的任何有根据的猜测。
只需执行
(ql:quickload "restas") 即可重现该错误。然后评估上面给出的 block 。这给出了 Error: The value NIL is not of the expected type STRING.我不熟悉在 LISP 中使用其他人的代码，所以我对如何进行有点困惑。更多信息 :这是对
define-method 的调用给出这个错误，源是文件policy.lisp here ，目前这有点超出我的理解。我试过
sbcl也:* (ql:quickload "linkdemo")
To load "linkdemo":
Load 1 ASDF system:
linkdemo
; Loading "linkdemo"
.
;;; Checking for wide character support... WARNING: Lisp implementation doesn't use UTF-16, but accepts surrogate code points.
yes, using code points.
;;; Building Closure with CHARACTER RUNES
.........
debugger invoked on a SB-KERNEL:CASE-FAILURE in thread
#<THREAD "main thread" RUNNING {10004F04C3}>:
NIL fell through ETYPECASE expression.
Wanted one of (SIMPLE-STRING STRING SB-FORMAT::FMT-CONTROL).
...
(SB-FORMAT::%FORMAT #<SB-IMPL::CHARACTER-STRING-OSTREAM {1003BD1673}> NIL ("UPVOTE-COUNT") ("UPVOTE-COUNT"))
0]
最佳答案
仅定义一种方法时，我可以重现测试用例:
(restas:define-policy datastore
(:interface-package #:linkdemo.policy.datastore)
(:interface-method-template "DATASTORE-~A")
(:internal-package #:linkdemo.datastore)
(define-method init ()
"Initiate the datastore"))
这里的问题是，当您展开上述宏时，您会获得对
RESTAS::%DEFINE-POLICY 的函数调用。在哪里 :INTERNAL-FUNCTION-TEMPLATE给出 NIL ，这不是适当的格式字符串。这是因为 define-policy 的方式宏解析选项。这是一个简化的示例:
(defun my-function (&key (x 0))
(print x))
MY-FUNCTION :x 的默认值为 0 .如果您调用(my-function) ，它打印 0。但宏执行如下操作:(defmacro my-macro (args)
(let ((x-arg))
(loop for (k v) in args
do (case k (:x (setf x-arg v))))
`(my-function :x ,x-arg)))
它遍历参数列表以检查
:x 的某些关键字是否参数存在，然后将一个局部变量(初始化为 nil)设置为相应的值。在所有情况下，它都会扩展为对
my-function 的调用。并显式绑定(bind) x值为 x-arg ，即使它为零。事实上，如果我们宏展开 (my-macro ()) , 如果给出 (my-function :x nil) .由于函数已经定义了默认值，我们希望避免在其他地方重复这个默认值，所以宏应该注意不要给出
:x当其对应的值为 nil 时。或者更准确地说，当关键字参数不存在时(这里我不区分两种情况)。通常，这样做如下:(defmacro my-macro (args)
(flet ((maybe (k v) (and v (list k v))))
(let ((x-arg))
(loop for (k v) in args do (case k (:x (setf x-arg v))))
`(my-function ,@(maybe :x x-arg)))))
,@拼接运算符用于根据值是否为 nil 将关键字参数注入(inject)到调用中。为 nil 时，拼接空列表。否则，属性列表 (list k v)是拼接的。因此，调用 (my-macro ())现在扩展为 (my-function) ，因此 x将采用其默认值。这没有经过很好的测试，但我想你可以重新定义
define-policy 如下:(defmacro define-policy (name &body body)
(let (methods
internal-package internal-function-template
interface-package interface-method-template)
(iter (for item in body)
(case (car item)
(:internal-package
(setf internal-package (second item)))
(:internal-function-template
(setf internal-function-template (second item)))
(:interface-package
(setf interface-package (second item)))
(:interface-method-template
(setf interface-method-template (second item)))
(otherwise
(cond
((string= (car item) "DEFINE-METHOD")
(push (cdr item) methods))
(t
(error "Unknown DEFINE-POLICY option: ~A" item))))))
(flet ((maybe (key value) (and value (list key value)))
(maybe/quote (key value) (and value (list key `(quote ,value)))))
`(eval-when (:compile-toplevel :load-toplevel :execute)
(%define-policy ',name ',methods
,@(maybe/quote :interface-package interface-package)
,@(maybe :interface-method-template interface-method-template)
,@(maybe/quote :internal-package internal-package)
,@(maybe :internal-function-template internal-function-template))))))
或者，只需添加
:internal-function-template参数(例如 "~A" )到您的宏。已修补:https://github.com/archimag/restas/commit/81bbbab6b36f81f846f78e71232e9d3d15f6d952
关于common-lisp - Lisp Webtales 第 5 章 - 如何让它工作，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/58257183/