HELP! Using try / catch statements! 2

[Burtlancaster]

Can someone please put me out of my misery! I cannot for the life work the following problem out.

Basically I would like to take an entered value from a TextBox (a string value) and convert it to a float! Simple! I know, but what happens if the user enters a non-digit expression (letters,symbols etc), using the "StrToFloat" method the program will simply return for example "Edit is not a valid floating point value." now what I want to do is catch this Expression and display my own message so I have tried the following code

//----------------------------------------------
#include <vcl.h>
#pragma hdrstop
#include "Unit1.h"
//----------------------------------------------
#pragma package(smart_init)
#pragma resource "*.dfm"
TForm1 *Form1;
//----------------------------------------------
__fastcall TForm1::TForm1(TComponent* Owner)
    : TForm(Owner)
{
}
//----------------------------------------------
void __fastcall TForm1::Button1Click(TObject *Sender)
{
try
  {
  float EditText=StrToFloat(Edit->Text);
  Edit->Text=FloatToStrF(EditText,ffFixed,8,2);
  }
catch (...)
  {
  ShowMessage("non value entered");
  }
}
//----------------------------------------------

But the code will never see the catch instead whilst in debug it will display a EConvertError, and then say "Edit1 is not a valid floating point value." So how do I say hang on a minute if it cant convert it then do / say this...

Anyway I'll leave the problem in you capable hands.

Thanks for looking and any input would be much appreciated.

 

[2ffat]

The try...catch statements are always overridden by debug. If you resume your program after debug catches a problem, your try...catch statement will execute.

Once you disable the debugging, the program will execute as expected.

James P. Cottingham
-----------------------------------------
[sup]I'm number 1,229!
I'm number 1,229![/sup]

 

[BuilderSpec]

The other way is to validate the input into the text box as it is keyed!

use the KeyPress event to check that only numbers and 1 decimal point can be keyed...

void __fastcall TForm1::Edit1KeyPress(TObject *Sender, char &Key)
{
if ( Key < '0' || Key > '9' )
{
if ( Key != '.' )
Key = 0;
else
if ( Edit1->Text.Pos(".") > 0 )
Key = 0;
}
}


Regards

BuilderSpec

 

[Burtlancaster]

you know its always the simple things that work the best, and your method BuilderSpec works a treat and I dont know why i didnt think of that myself. thanks.

 

[c567591]

The try/catch would probably work fine outside the debugger.
Sometimes I debug outside the debugger with message boxes and logging.