如何不接受 Delphi 10.3 上的字符串中的特殊字符

Question

I am trying to write a program for my school-based assignment. It is supposed to accept names as string s, and a salary input as an integer , and tell you whether you are illegible or able to participate in party sections, and repeats until stop=9 .

Everything went well, but the issue is the string variables accept erroneous names as inputs and continue. For example 'John32@#$^^' .

I want the program to not accept these inputs, and write a line stating that it will not continue with any name with anything other than characters. This should also not add a number to stop. The source code is below.

program Sba;

Uses
  Windows;

var
  FName,LName:String;
  Stop,Salary:Integer;

//procedure Sleep(milliseconds: Cardinal); stdcall; external 'kernel32.dll'; //Added sleep as a procedure for delay

Begin
  Repeat //Repeats until stop = 9
    Writeln('Hi User,please Enter your First Name'); //Prompting user to enter their First initials
    Readln(FName); //Attaches the string entered to the variable FName
    Sleep(1000);//Delay 1second
    Writeln('First Name entered');  //Lets the user know they have entered their first initials
    Sleep(1000);
    Writeln('Please Enter your Last name'); //Prompting user to enter their last initial
    Readln(LName);  //Attaches the string entered to the variable LName
    Sleep(1000);
    Writeln('Last Name entered'); //Lets the user know they have entered their last initials
    Sleep(800);
    Writeln('Hi ',' ',FName,' ',LName); //Writes Line Hi (First Name) (Last Name)
    Sleep(1000);
    Writeln('Please enter The amount you have paid');//Prompts user for their payment
    Readln(Salary); //Atttached value entered to Salary
    Writeln('Reading your payment will be done in four seconds');
    Sleep(4000);//delay 4 seconds
    Writeln('Done!');
    If (Salary<1000) Then
    Begin
      Writeln('You do not have sufficient funds to play in a section');
    Sleep(1000);
    End;
    Sleep(1000);
    If (Salary>=1000) AND (Salary<=2000) then //Testing conditions
    Begin
      Sleep(1000);
      Writeln('Congrats, You are eligible to play in the Tribe Section'); //Tells use what section they are available to play in
    End;
    If (Salary>=2100) AND (Salary<=3000) then //Testing conditions
    Begin
      Sleep(1000);
      Writeln('Congrats, You are eligible to play in the Poison Section');
    End;
    If (Salary>=3100) AND (Salary<=5000) then //Testing conditions
    Begin
      Sleep(1000);
      Writeln('Congrats, You are eligible to play in the Harts Section');
    End;
    Writeln('Press enter to continue');
    Readln;
    Writeln('Enjoy your day ' , FName,'!');
    Stop:=Stop+1; //Repeats until stop= 9
    Sleep(1000);
  Until Stop=9;//Repeats this 10 times
  Writeln('Written By Timothy Adams 4-1');
  Readln;
end.

Answer 1

Since this is homework, I will not give you exactly what you ask for. Instead, I'll give you a somewhat more involved example to study.

First, we must decide what a valid name looks like. Because if we don't know exactly what names are to be considered valid, we surely cannot program a computer to tell the difference!

Just as a toy example, let's say that a name is valid iff :

1. It contains only letters, whitespace, and the HYPHEN-MINUS (-) character. [Notice that everything in a string is a character. Examples of character classes are letters, digits, whitespace, and punctuation. So when you say that the string must only contain "characters", you mean something else, like "only letters".]

2. It contains at least two letters.

This is by far not good enough for a real-world application. It would disallow many valid names. But it is good enough for this toy example.

Let's implement this!

function IsValidName(const S: string): Boolean;
var
  i, c: Integer;
begin

  // The string must only contain letters, whitespace, and HYPHEN-MINUS

  for i := 1 to S.Length do
    if not (S[i].IsLetter or S[i].IsWhiteSpace or (S[i] = '-')) then
      Exit(False);

  // The string must contain at least two letters

  c := 0;
  for i := 1 to S.Length do
    if S[i].IsLetter then
      Inc(c);

  if c < 2 then
    Exit(False);

  Result := True;

end;

Study this function until you fully understand how it works!

Done? Great: Now let's make use of it:

program Project1;

{$APPTYPE CONSOLE}

{$R *.res}

uses
  System.SysUtils,
  Character;

var
  Name: string;

function IsValidName(const S: string): Boolean;
begin
  // same as above, won't repeat it here
end;

begin
  try
    try

      Writeln('Hello! What is your name?');

      while True do
      begin
        Readln(Name);
        Name := Name.Trim;
        if IsValidName(Name) then
        begin
          Writeln('Welcome, ', Name, '!');
          Break;
        end
        else
          Writeln('Surely that isn''t your real name? What is your actual name?');
      end;

    except
      on E: Exception do
        Writeln(E.ClassName, ': ', E.Message);
    end;
  finally
    Writeln('Program about to end. Press Return to exit.');
    Readln;
  end;
end.

Again, since I am almost breaking the rules by doing your homework for you, I won't explain the logic in detail. Instead, I'll let you figure out how it works for yourself. That way you will learn a lot more.

Update: The complete program should look like this:

program Project1;

{$APPTYPE CONSOLE}

{$R *.res}

uses
  System.SysUtils,
  Character;

var
  Name: string;

function IsValidName(const S: string): Boolean;
var
  i, c: Integer;
begin

  // The string must only contain letters, whitespace, and HYPHEN-MINUS

  for i := 1 to S.Length do
    if not (S[i].IsLetter or S[i].IsWhiteSpace or (S[i] = '-')) then
      Exit(False);

  // The string must contain at least two letters

  c := 0;
  for i := 1 to S.Length do
    if S[i].IsLetter then
      Inc(c);

  if c < 2 then
    Exit(False);

  Result := True;

end;

begin
  try
    try

      Writeln('Hello! What is your name?');

      while True do
      begin
        Readln(Name);
        Name := Name.Trim;
        if IsValidName(Name) then
        begin
          Writeln('Welcome, ', Name, '!');
          Break;
        end
        else
          Writeln('Surely that isn''t your real name? What is your actual name?');
      end;

    except
      on E: Exception do
        Writeln(E.ClassName, ': ', E.Message);
    end;
  finally
    Writeln('Program about to end. Press Return to exit.');
    Readln;
  end;
end.