我正在尝试创建一个程序，该程序需要用户输入并检查其有效期是否为日期（2000年至2099年）。当我对代码进行错误测试时，我连续两次将Enter输入作为输入，第一次输入Enter时，未引发任何错误，但第二次控制台闪烁消息并崩溃。我拍了一张截图，因为它崩溃了，这是它显示的错误
An unhandled exception occured at $0040CDE1
EConvertError : "" is an invalid integer
我最好的猜测是该错误是由我的StrToInt中的一个人EConvertError引起的，但是我不清楚为什么它只在第二遍而不是第一遍中抛出。我怀疑该错误发生在85、98、111或195的任一行上。
当我最初编写该程序时，a是Pascal的初学者，因此我对任何草率的代码表示歉意。
下面是所有代码，如果您想自己运行。
program DateVerifierAssignment;
uses crt, sysutils;
var
userInputArray: array[0..7] of string;
len, i, day, month, year: integer;
date, userInput, stringDay, stringMonth, stringYear: string;
errorCatch: boolean;
//DECLARING FUNCTIONS & PROCEDURES
procedure TitleScreen();
begin
//prints a coloured wall of text to give information like name and instructions
WriteLn(' o-------------------------o');
Write(' | ');TextColor(White);Write('Date Validation Program');TextColor(Cyan);WriteLn(' |');
WriteLn(' o-------------------------o');
WriteLn();
WriteLn(' o-------------------------o');
Write(' | ');TextColor(White);Write('Instructions');TextColor(Cyan);WriteLn(' |');
WriteLn(' o-------------------------o');
Write(' | ');TextColor(White);Write('Enter a date and the');TextColor(Cyan);WriteLn(' |');
Write(' | ');TextColor(White);Write('program will verify it');TextColor(Cyan);WriteLn(' |');
Write(' | ');TextColor(White);Write('and convert it to its');TextColor(Cyan);WriteLn(' |');
Write(' | ');TextColor(White);Write('long form');TextColor(Cyan);WriteLn(' |');
WriteLn(' o-------------------------o');
WriteLn();
TextColor(White);
Write(' press any key to begin');
//waits for user input then clears the screen and returns the text color to white
ReadKey();
ClrScr;
end;
function DateVerification(var userInput: string): boolean;
var
errorLimit : boolean;
bounds: integer;
begin
errorLimit := True;
//stores the length of the string as a variable
len := Length(userInput);
//checks to see if entry is 8 chracters long and displays an error message and returns user to input screen if it doesn't fit
if (len <> 8) and (errorLimit = True) then
begin
ClrScr();
TextColor(Red);
WriteLn('input was not the right length (8 characters)');
TextColor(White);
Write('make sure date fits format ');
TextColor(LightGreen);
WriteLn('dd/mm/yy');
TextColor(White);
Readkey();
ClrScr();
errorLimit := false;
Dateverification := false;
end;
//spits each character into its own spot in an array
for i := 1 to len do
userInputArray[i - 1] := userInput[i];
//tests if every slot in the array where a slash should be is a slash
for i := 0 to len-1 do
begin
if (userInputArray[2] <> '/') or (userInputArray[5] <> '/') and (errorLimit = true) then
begin
ClrScr();
TextColor(Red);
WriteLn('input did not have slashes in correct locations ');
TextColor(LightGreen);
WriteLn('dd/mm/yy');
TextColor(White);
Readkey();
ClrScr();
errorLimit := false;
Dateverification := false;
end;
end;
year := ((StrToInt(userInputArray[6]))*10) + StrToInt(userInputArray[7]);
if (year < 1) or (year > 99) and (errorLimit = true) then
begin
ClrScr();
TextColor(Red);
WriteLn('year was not from 0 to 99');
TextColor(White);
Readkey();
ClrScr();
errorLimit := false;
Dateverification := false;
end;
month := ((StrToInt(userInputArray[3]))*10) + StrToInt(userInputArray[4]);
if (month < 1) or (month > 12) and (errorLimit = true) then
begin
ClrScr();
TextColor(Red);
WriteLn('month was not from 1 to 12');
TextColor(White);
Readkey();
ClrScr();
errorLimit := false;
Dateverification := false;
end;
day := ((StrToInt(userInputArray[0]))*10) + StrToInt(userInputArray[1]);
if (month = 4) or (month = 6) or (month = 9) or (month = 11) then
bounds := 30;
if (month = 2) then
begin
if (IsLeapYear(year) = true) then
bounds := 29
else
bounds := 28;
end
else
bounds := 31;
if (day < 1) or (day > bounds) and (errorLimit = true) then
begin
ClrScr();
TextColor(Red);
WriteLn('day was not from 1 to days in month');
TextColor(White);
Readkey();
ClrScr();
errorLimit := false;
Dateverification := false;
end;
if (errorLimit = true) then
DateVerification := True;
end;
function IsLeapYear(var year: integer): boolean;
//simple function to determine if a year is a leap year on the gregorian calender
begin
if (year mod 4) = 0 then
if (year mod 100 <> 0) then
if (year mod 400 = 0) then
IsLeapYear := true
else
IsLeapYear := false
else
IsLeapyear := false
else
IsLeapyear := false
end;
procedure DateToAlpha(var userInput: string);
begin
end;
//MAIN PROGRAM
begin
//preparing for while loop later in code and changes text colour to cyan
errorCatch := true;
TextColor(Cyan);
//Displays a title screen and instruction about how to use(stored in a procedure to help with readability)
TitleScreen();
//begins a loop so that if an error is to occur the program can easily ask for a new date and try again
while (errorCatch = true) do
begin
//sets error catch to 0 so that if there a no errors the program will not loop
errorCatch := false;
//displays information on how to input a date as well as an example with different colours for better readability
Write('Enter a date in the format');TextColor(LightGreen); WriteLn(' dd/mm/yy');TextColor(White);
Write('e.g. ');TextColor(LightGreen);WriteLn(' 09/07/20'#13#10);TextColor(White);
//takes date user inputs and stores it
ReadLn(userInput);
//calls the date verification function to see if the date is valid
//(refer to dateVerification at the top of the program for more info and comments)
if (DateVerification(userInput) = false) then
errorCatch := true;
len := Length(userInput);
for i := 1 to len do
userInputArray[i - 1] := userInput[i];
year := ((StrToInt(userInputArray[6]))*10) + StrToInt(userInputArray[7]);
readKey();
end;
end.
答案 0 :(得分：3)
通常在SO上，我们不提供对qs的完全编码答案，这显然是课程的工作。
在这种情况下，我以为我会例外，因为很明显您在 不必要的恶劣天气，以及您编码的方式实际上可能会妨碍您 调试并使其正常工作。
因此，以下示例显示了一个非常简单的例子， 验证以dd / mm / yyyy格式提供的21世纪日期的简洁方法。它 显示正确的处理和验证步骤顺序；如果检测到错误 在任何步骤中，它都会说明问题所在并停止。如果执行一直持续到最后， 提供的日期字符串必须有效。
我故意遗漏了任何循环 或美化代码，因为首先正确无误是一件很简洁的事情 处理和验证步骤的编码。如果您想使用循环，那很好，但是您使用的方式 例如errorCatch，我敢打赌，如果您在6个月内回到代码中，您将不记得如何 它应该工作。您不需要任何复杂的标志或循环来执行此任务-用户只需要能够准确键入八个字符（后接[Enter]），然后代码就会告诉您它是否有效。
请注意，我已经使用了标准的“复制”功能来分离出 输入的日期。顺便说一句，你的声明
userInputArray: array[0..7] of string;
完全是错误的。如果您想要一个由一定数量的字符组成的数组，可以，但是
只是不必要地使用户输入内容的处理和处理复杂化。很远
更简单，因此不太容易接受8个字符的单个 string 字符串
并处理。但是无论如何，要允许字符串在日期和月份的数字后包含/字符，字符串的长度应为10，而不是8，以允许这些数字和四年的数字。
program DateVerification;
uses
SysUtils;
var
sUserInput,
sDay,
sMonth,
sYear : String;
iDay,
iMonth,
iYear,
iDays: Integer;
bIsLeapYear : Boolean;
function DaysInMonth(iMonth, iYear : Integer) : Integer;
begin
Result := -1; // you supply the code for this taking into account leap year for February
end;
begin
writeln('Please enter a date between 01/01/2000 and 31/12/2099 in the format shown');
readln(sUserInput);
if Length(sUserInput) <> 10 then begin
writeln('Input is wrong length.');
Halt;
end;
if (sUserInput[3] <> '/') or (sUserInput[6] <> '/') then begin
writeln('Input is incorrectly delimited.');
Halt;
end;
sDay := Copy(sUserInput, 1, 2);
sMonth := Copy(sUserInput, 4, 2);
sYear := Copy(sUserInput, 7, 4);
iYear := StrToInt(sYear);
if (iYear < 2000) or (iYear > 2099) then begin
writeln('Invalid year : ', sYear);
Halt;
end;
bIsLeapYear := IsLeapYear(iYear); // you supply the code for IsLeapYear
iMonth := StrToInt(sMonth);
if (iMonth < 1) or (iMonth > 12) then begin
writeln('Invalid month : ', sMonth);
Halt;
end;
iDay := StrToInt(sDay);
if (iDay < 1) or (iDay > DaysInMonth(iMonth, iYear)) then begin
// You need to supply the DaysInMoth function, which of course
// needs to account for February in a leap year
writeln('Invalid day of month: ', sMonth);
Halt;
end;
writeln(sUserInput, ' is a valid date.');
readln;
end.