How do I override TRichEdit.Lines.Add ?

Posted on 2011-02-10
Last Modified: 2012-05-11
I need to override TRichEdit.Lines.Add in order to do some processing there, before adding the text in the RichEdit. How can I do that? Can I do that directly?
Question by:cubic77
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LVL 32

Expert Comment

by:Ephraim Wangoya
ID: 34864597

Not exactly, the TStrings.Add method itself can be overriden but TRichEdit is not structured in such a way to allow you to do that easily

you can go around it by using the code as follows in your form unit
  TRichEdit = class(ComCtrls.TRichEdit)
    function Add(const AString: string): Integer; 
  TForm1 = class(TForm)


function TRichEdit.Add(const AString: string): Integer;
  NewString: string;
  //do something with the string and assign the new value to NewString
  Result := Lines.Add(NewString);

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LVL 32

Expert Comment

by:Ephraim Wangoya
ID: 34864613
So instead of using

you will use

Author Comment

ID: 34864789
Thanks, but I already implemented exactly the same thing. Until I get the answer to my original question, this solution is acceptable but far from good. Why I don't consider it a GOOD solution? Because I have to remember that I have to use the exception (RichEdit.Add) instead of the normal method.

So, probably in 3-4 months I will accidentally use RichEdit.Lines.Add and I will start to wonder why my RichEdit is not working as expected.
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Author Comment

ID: 34864822
Actually this solution will became GOOD if the is a way to make the original method (lines.add) not to work anymore. In this case obviously I will see the error message while trying to use it and I will probably remember to use the new method.
LVL 32

Accepted Solution

Ephraim Wangoya earned 500 total points
ID: 34864849
In that case you will have to encapsulate the TRichEdit in a new control, then expose the public methods of TRichEdit and install that control in your component palette.

Then replace all your TRichEdit controls with the new one.

I can show you how to do that, but right now I'm working on something

Author Comment

ID: 34864914
> I can show you how to do that, but right now I'm working on something
No. I got it. Thanks.

I also had that idea. What I actually wanted was to see if there is any way to override (for real) the Add method.

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