Ошибка в делфи is not a valid integer value

I’ve got a program that asks the user to enter a value (in an Edit box) and then when he clicks on the Show Value button, the Label should say «The value of x is » plus whatever value he entered in the Edit box.

But Delphi is complaining saying «x is not a valid integer value.»

I don’t know what’s wrong with my code but here is what I’ve got:

var
  FormSimpleVariable: TFormSimpleVariable;
  x : integer;

implementation

{$R *.dfm}

procedure TFormSimpleVariable.ButtonQuitClick(Sender: TObject);
begin
  Application.Terminate;
end;

procedure TFormSimpleVariable.ButtonShowValueClick(Sender: TObject);
begin
  x := StrToInt('x');
  LabelResult.Caption := 'The value of x is ' + IntToStr(x);
end;

end.

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Do you understand what StrToInt() actually does?  What do you think StrToInt(‘x’) should do, and why do you think it should NOT throw an error (hint: it SHOULD)?  The string ‘x’ is not representative of a valid integer value, so of course it can’t be converted into an actual integer.

You said the user is entering a value in an Edit box, but this code is not accessing that Edit box at all.

You need something more like this instead:

procedure TFormSimpleVariable.ButtonShowValueClick(Sender: TObject);
var
  x: Integer;
begin
  x := StrToInt(EditValue.Text);
  LabelResult.Caption := 'The value of x is ' + IntToStr(x);
end;

Alternatively, for numeric input, consider using a more appropriate UI control, like TSpinEdit or TNumberBox, which provide the input as actual integers rather than as strings.

Edited April 28 by Remy Lebeau

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considere (too) alternative «Def» function to: StrToxxxDef(…, …)

Quote

    StrToIntDef(‘your number here’, 0);
    StrToInt64Def(‘your number here’, 0);
    StrToFloat()
    StrToUInt64()
    StrToUInt64Def()
    StrToFloatDef()

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I had to read this question x times before I understood it

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How come you can’t assign a value to a variable in the same section you declared it? You gotta assign the value underneath the begin keyword instead.

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1 hour ago, David Heffernan said:

before I understood it

your CPU it’s very fast… there is a delay time… it’s ok!  😂

…1, 2, 3, 5, 8… ops! starting again…  bip! bip! 

Edited April 28 by programmerdelphi2k

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You guys are acting like jerks. I’m talking about a different piece of code now. If you can’t or don’t know how to be nice and respectful, then please go to bed.

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49 minutes ago, 357mag said:

How come you can’t assign a value to a variable in the same section you declared it? You gotta assign the value underneath the begin keyword instead.

where do you assign it in c++/pick one ? before the «{«/pick one ?

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5 hours ago, programmerdelphi2k said:

considere (too) alternative «Def» function to: StrToxxxDef(…, …)

And alternatively, the TryStrToxxx() functions.

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@Remy Lebeau

right!  but «StrToxxxxxxDEF(….)» it’s more flexible (it dont needs a «var» to receive «out param…»)

var
  v: integer; // mandatory to TryStrToxxxx(...)
begin
  TryStrToInt('x', v); // more conservadore
  (*
    function TryStrToInt(const S: string; out Value: Integer): Boolean;
    var
    E: Integer;
    begin
	    Val(S, Value, E);
	    Result := E = 0;    // exchanging 6 for half a dozen
    end;
  *)
  //
  StrToIntDef('x', 0); // more flexible
  (*
    function StrToIntDef(const S: string; Default: Integer): Integer;
    var
    E: Integer;
    begin
	    Val(S, Result, E);
	    if E <> 0 then
        	Result := Default;  // exchanging 6 for half a dozen
    end;
  *)

  // at end, if works it's good too!

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4 hours ago, 357mag said:

I had to assign the values to the variables further down underneath the begin keyword.

In c++, you are also assigning it after the «begin».

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yahooo!!!! 

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If StrToInt says a string is not a number thus it can not be converted, trust it, it’s true.

If you are really interested, you can use the function «Val» which will even tell you which character is causing it to fail.

You might want to sanitize your input first for spaces or other non-printable characters which get there easily if you copy-paste from documents / websites.

Also, consider what @Remy Lebeau said, and use a TSpinEdit or TNumberBox instead (you can check NumbersOnly in TEdit as well). This way the input won’t even be accepted if the pasted string / typed character is not a number.

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I’m guessing what happened here is that asker put the variable name into a string and imagined it would be interpreted in the context of the variable namespace. 

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19 hours ago, programmerdelphi2k said:

but «StrToxxxxxxDEF(….)» it’s more flexible (it dont needs a «var» to receive «out param…»)

On the other hand, the StrToxxxDef() functions don’t let you differentiate whether valid vs invalid input was entered unless you use a sentinel value that can’t appear in any valid input.  The TryStrToxxx() functions let you differentiate very easily.  Besides, what is the point of converting a string to an integer/floating type if you are not going to use the converted value anyway?

var
  v: integer;
begin
  // don't ignore the return value!
  // TryStrToInt('...', v);
  if TryStrToInt('...', v) then begin
    // use v as needed ...
  end else begin
    // error converting ...
  end;

  // don't ignore the return value!
  // StrToIntDef('...', 0);  
  v := StrToIntDef('...', 0);
  if v <> 0 then begin
    // use v as needed ...
  end else begin
    // was the input actually '0', or did an error occur ???
  end;
end;

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59 minutes ago, aehimself said:

Also, consider what @Remy Lebeau said, and use a TSpinEdit or TNumberBox instead (you can check NumbersOnly in TEdit as well). This way the input won’t even be accepted if the pasted string / typed character is not a number.

Do note that setting TEdit.NumbersOnly=true merely tells the TEdit to accept only digit characters and no others (so, no negatives, no decimals, etc) , but it will not validate that the text as a whole will convert to a valid integer. So you still have to handle that conversion yourself, if you don’t use a UI control that does it for you.

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34 minutes ago, Remy Lebeau said:

if you are not going to use the converted value anyway?

The excence of the alternative functions in question is the same!

•   Val(S, Value, E);

What distinguishes the two is just how the return is reported to the user:

1. returns a boolean;
2. the other an integer;

however, the «out» parameter has the same function: capture the value, a value «pre-defined» by the user, and use it: either through a variable informed by the user, or through the return of the function.

• they are two flavors of the same fruit!

// none error at all, just "is valid or not?"
var
  LResult: integer;
begin
  if StrToIntDef('hello', 0) = 0 then
    ShowMessage('bye bye');
  //
  LResult := StrToIntDef('hello', 0);
  //
  if (LResult = 0) then
    ShowMessage('bye bye');
  //
  //
  if TryStrToInt('hello', LResult) then { ... };
  //
  if (LResult = 0) then
    ShowMessage('bye bye');

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The point about return value vs out param is that the former can be composed directly in chained function calls. 

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if TryStrToInt('hello', LResult) and (LResult >0) then
	ShowMessage(' it,s good for us :) ');

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I don’t recall adding those single quotes around x (like (‘x’)). Don’t know what happened there. Mistakes and being human I guess.

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7 hours ago, 357mag said:

I don’t recall adding those single quotes around x (like (‘x’)). Don’t know what happened there. Mistakes and being human I guess.

Without those quotes the code would not compile…

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On 4/28/2023 at 7:10 PM, 357mag said:

I’ve got a program that asks the user to enter a value (in an Edit box) and then when he clicks on the Show Value button, the Label should say «The value of x is » plus whatever value he entered in the Edit box.

But Delphi is complaining saying «x is not a valid integer value.»

I don’t know what’s wrong with my code but here is what I’ve got:

var
  FormSimpleVariable: TFormSimpleVariable;
  x : integer;

implementation

{$R *.dfm}

procedure TFormSimpleVariable.ButtonQuitClick(Sender: TObject);
begin
  Application.Terminate;
end;

procedure TFormSimpleVariable.ButtonShowValueClick(Sender: TObject);
begin
  x := StrToInt('x');
  LabelResult.Caption := 'The value of x is ' + IntToStr(x);
end;

end.

simply change your line from

  x := StrToInt('x');

to

  x := StrToInt(inttostr(x));

crazy, but will work. But I do not understand why someone would do this 

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