Is there a way I can validate multiple inputs through InputBox for integers?-CodePudding

I am basically new to Delphi and I have been given an assignment where I have to sort an integer array, and also validate every input.

I have taken inputs of the array through the InputBox() function. The code for which goes like this:

procedure TForm1.Button1Click(Sender: TObject);
begin
  for i := 0 to Length(arr)-1 do
  begin
    arr[i] := StrToInt(InputBox('Program to sort integers', 'Enter 5 integers', ''));
  end;

I have also tried putting a try..except block to catch errors, but it is not working as expected. The try..except block goes something like this:

procedure TForm1.Button1Click(Sender: TObject);
begin
  for i := 0 to Length(arr)-1 do
  begin
    try
      arr[i] := StrToInt(InputBox('Program to sort integers', 'Enter 5 integers', ''));
    except
      ShowMessage('Invalid input');
    end;

The problem is that on clicking the button, the above OnClick event handler gets executed, but the except block doesn't.

What should I now do so that input gets validated?

If you want to know more things about my form components, then I’ve added one label, one ListBox to display a sorted array and one button (which you know by name as Button1.)

Thanks in advance.

CodePudding user response：

Using the OnKeyPress() event as you show in your comment! But, if you want that the user can simply hit Enter to mark the end of a value, you also need to accept #13 as a valid key.

Thus, the first test in the OnKeyPress event becomes

if not (Key in [#8, #13, '0'..'9']) then
begin
  Key := #0;
  Exit;
end;

Then you need to handle the #13 key: (pseudocode)

if key = #13 then
begin
  // get the value of entered digits using `StrToInt()` function
  // to generalize, use `TEdit(Sender)` to refer to the current edit control
  // verify value against min and max values
  // if previous test succeeds, 
    // add to array
    // clear the edit control text
  // else show error msg
end

All other accepted keys are handled by the control.

CodePudding user response：

You can't restrict InputBox but you can make your own InputBox with a simple form with Edit box and label and buttons.
To restrict edit box to accept only integers of certain range you have to options :

Make a new Edit class inherited from TEdit



      TIntegerEdit = class(TEdit)
      protected
        procedure KeyDown(var Key: Word; Shift: TShiftState); override;
        procedure KeyUp(var Key: Word; Shift: TShiftState); override;
        procedure KeyPress(var Key: Char); override;
        procedure DoEnter; override;
        procedure DoExit; override;
      end;

2)Use TEdit events to reach your goal. Look at the following sample.

Our form contains an edit control and two buttons. The Edit OnKeyUp & OnKeyDown use the same event.



  TForm1 = class(TForm)
    Edt1: TEdit;
    BtnOk: TButton;
    BtnCancel: TButton;
    procedure Edt1KeyDown(Sender: TObject; var Key: Word; Shift: TShiftState);
    procedure Edt1KeyPress(Sender: TObject; var Key: Char);
    procedure Edt1Enter(Sender: TObject);
    procedure Edt1Exit(Sender: TObject);
  private
    { Private declarations }
    FOldText : string;
  public
    { Public declarations }
  end;

Here is the code used to restrict the Edit to range 1000 to 5000.



    procedure TForm1.Edt1KeyDown(Sender: TObject; var Key: Word; Shift: TShiftState);
    begin
      // if not in range '0' .. '9' , VK_BACK, VK_TAB, VK_RETURN
      if not ((Key in [48..57]) or (Key in [VK_BACK, VK_TAB, VK_RETURN])) then
        Key := 0;
    end;
    
    procedure TForm1.Edt1KeyPress(Sender: TObject; var Key: Char);
    var
      i : Integer;
    begin
      if not ((Key in ['0'..'9']) or (Ord(Key) in [VK_BACK, VK_TAB, VK_RETURN])) then
        Key := #0;
    end;
    
    procedure TForm1.Edt1Enter(Sender: TObject);
    begin
      FOldText := '';
      Edt1Exit(Self);
      FOldText := Edt1.Text;
    end;
    
    procedure TForm1.Edt1Exit(Sender: TObject);
    const
      MinVal = 1000;
      MaxVal = 5000;
    var
      IntVal, E: Integer;
    begin
      Val(Edt1.Text, IntVal, E);
      if E  0 then //Do we have an error?
        Edt1.Text := FOldText;
    
      if (IntVal  MaxVal) then
        Edt1.Text := FOldText;
    end;