[Okta Webinar] Learn how to a build a cloud-first strategyRegister Now

x
?
Solved

Validate TEdit to allow only valid file name characters?

Posted on 2015-02-19
6
Medium Priority
?
360 Views
Last Modified: 2015-05-30
Hi! In a Delphi XE7 VCL application, at runtime I need to validate the text input inside a TEdit to allow only valid file name characters. In Delphi XE7 there is the System.IOUtils.TPath.HasValidFileNameChars function. How can this be applied in real-time in a TEdit component?

Unfortunately, the TEdit component has no OnValidating event. I don't want to use the OnChange event, because it looks ugly when the character appears for a short time. The validation must occur BEFORE the character appears.
0
Comment
Question by:PeterDelphin
  • 2
4 Comments
 
LVL 24

Expert Comment

by:jimyX
ID: 40620411
You can make use of one of the KeyDown/KeyUp/KeyPress events which enables you to check the pressed key before it is printed to the component.

procedure TForm1.Edit1KeyPress(Sender: TObject; var Key: Char);
begin
  if Key in ['a'..'z', 'A'..'Z','\', ..etc]  // List all the allowed Char ranges
  if not TPath.HasValidFileNameChars(Edit1.Text+Key, ...) // Or check the key if is not valid just reset the key
    Key:= #0;
end;
0
 

Author Comment

by:PeterDelphin
ID: 40623965
This is not reliable, as one can paste still PASTE chars which are not allowed as filename.
0
 
LVL 24

Accepted Solution

by:
jimyX earned 1000 total points
ID: 40624087
In this case you have to use OnChange event, but with a unique technique, I will show you how to avoid the invalid-chars appearance.

procedure TForm1.Edit1Change(Sender: TObject);
begin
  if not HasValidFileNameChars(TEdit(Sender).Text,..) then
    begin
      TEdit(Sender).Undo; //Clear last entry it was not valid char
      Exit;
    end;

  TEdit(Sender).ClearUndo; //reset the Undo, when you have a valid entry
end;

Open in new window


Mahdi78 has wrote a wonderful article about utilizing Undo & ClearUndo. It worth reading it.
0
 
LVL 38

Assisted Solution

by:Geert Gruwez
Geert Gruwez earned 1000 total points
ID: 40660415
use a maskedit to allow only the characters you want
0

Featured Post

Technology Partners: We Want Your Opinion!

We value your feedback.

Take our survey and automatically be enter to win anyone of the following:
Yeti Cooler, Amazon eGift Card, and Movie eGift Card!

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Introduction The parallel port is a very commonly known port, it was widely used to connect a printer to the PC, if you look at the back of your computer, for those who don't have newer computers, there will be a port with 25 pins and a small print…
Creating an auto free TStringList The TStringList is a basic and frequently used object in Delphi. On many occasions, you may want to create a temporary list, process some items in the list and be done with the list. In such cases, you have to…
this video summaries big data hadoop online training demo (http://onlineitguru.com/big-data-hadoop-online-training-placement.html) , and covers basics in big data hadoop .
When cloud platforms entered the scene, users and companies jumped on board to take advantage of the many benefits, like the ability to work and connect with company information from various locations. What many didn't foresee was the increased risk…
Suggested Courses
Course of the Month19 days, 17 hours left to enroll

872 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question