Two methods of error handling

Two types of error handling: One is to redefine the error function, and one is to capture the error.

2. ;; ===================================================================================================
4. ;; ===================================================================================================
6. ;; =========================================== two kinds of error handling methods ========================================
8. ;; ===================================================================================================
10. ;; ===================================================================================================
14. ;; =============================================01. Error function ===========================================
18. (defun c:tt()
20.   ;; Backup system error Function
22. (setq *error*_bak *error*)
24.   ;; Assigning a custom error function to a system error function
26. ( setq *error* *error*_non)
28.   ;; Backup Capture
30. (setq osmode_bak ( GetVar "Osmode"))
34.   ;; ----------------------------------------
36. ( setvar "Osmode " 0)
38. (getpoint)
40. ( command " line" pause pause "")
42.   ;; ----------------------------------------
46.   ;; Normal execution also to restore the error function
48. ( setq *error* *error*_bak)
50.   ;; Normal execution also restores the modified variable
52. ( setvar "Osmode" osmode_bak)
54. )
58. ;; Define your own Error function
60. (defun *error*_non (msg)
62.   ;; Cancel execution of the use (command) of the CAD built-in command execution, and then execute the following statement
64. (command)
66.   ;; To restore a system error function
68. ( setq *error* *error*_bak)
70.   ;; Restore modified variables after an error
72. ( setvar "Osmode" osmode_bak)
74. )
80. ;; =============================================02. Error Capture ===========================================
84. ;; Function: whether the command exists
86. ;; Parameters: Command string
88. ;; Return value: exists as T, otherwise nil
90. (defun iscommandexist(commandstr / candcommandstr Isexist myvalue)
92. (setq candcommandstr (strcat "C:" commandstr))
94. (if (Equal (type ( eval (read candcommandstr))) ' subr)
96.     ;; Description is a command defined with Lisp's Defun .
98. (Progn
100. (setq isexist T)
102. ;(p rint "command exists!")
104.     )
106.     ;; Not a defun-defined command in Lisp
108. (progn
110. (if
112.         ;; If the condition of the Judgment
114. ( not
116.           ;; Catch error, error exists as T, does not exist as false
118. (vl-catch-all-error-p
120.             ;; The statement execution results are returned to myvalue, and the statement execution error myvalue value is #<%catch-all-apply-error%>, and no error is the result of the statement execution .
122. (setq myvalue
124.               ;; Execute the statement, and catch the error with vl-catch-all-apply, note the following format, first for the function note preceded by a single quote, followed by the function parameter table
125.               (vl-catch-all-apply'(Lambda (x) (Progn (Commandx) (setqLastcommand(GetVar "Lastprompt")) (if ( not (WcmatchLastcommand"* Unknown command *")) (Command "ESC")))) (ListCommandstr))
127.             )
129.           )
131.         )
133.         ;; The first statement after the IF condition
135.         ;; If you perform an error, execute the following sentence
137. (progn
139. (setq isexist nil)
141. ;(p rint "command does not exist!")
143.         )
145.         ;; The second statement after the IF condition
147.         ;; If the execution error occurs, catch the error and execute the following sentence
149. (progn
151. (setq isexist T)
153. ;(p rint "command exists!")
155.         )
157.       );; End If
159.       ;; Cancel command Operation
161. (if isexist
163. (Progn
165. (command)
167.         )
169.       );; End If
171.     );; End Progn
173.   );; End If
177.   ;; Output value, the command is t when it is present, otherwise nil
179. isexist
181. )

Two methods of error handling