How to make a dynamic memo in a class using delphi [closed] - delphi

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I have a form class TfrmWelcome and I want to be able to dynamically add
a memo to it when a button is clicked in the main part of the form (frmWelcome.MainPanelSourceEditor).
My unsuccessful attempt at some code is below. I get the error
"undeclared identifier WelcomeMemo". How could I get this to compile and work?
type
WelcomeMemo : TMemo;
end;
implementation
procedure SetHelpWelcome;
begin
WelcomeMemo : TMemo.Create(frmWelcome);
with TMemo(FindComponent('WelcomeMemo')) do
begin
Parent := frmWelcome.MainPanelSourceEditor;

Answer 1

If what you are trying to do is to add a memo to your frmWelcome at runtime, a better (but still not very good) way to do it would be like this:
procedure SetHelpWelcome;
var
WelcomeMemo : TMemo;
begin
WelcomeMemo := TMemo.Create(frmWelcome);
WelcomeMemo.Parent := frmWelcome.MainPanelSourceEditor;
// set any other properties of WelcomeMemo here.
end;
This avoids the with (which you should never use especially if you are a beginner) and the completely avoidable FindComponent to find something you don't need to find in the first place if you capture it by the assignment to the WelcomeMemo local variable.
But that's still a fairly naff way of doing what you want. It would be better to have the WelcomeMemo as a member of your form, and define a method of the form to create and initialise it; you could then call the method from the OnClick handler of the button you want to use to create it. Something like (untested)
TfrmWelcome = Class(TForm)
private
fWelcomeMemo : TMemo;
procedure SetUpWelcomeMemo;
[...]
end;
procedure TfrmWelcome.SetUpWelcomeMemo;
begin
if fWelcomeMemo <> Nil then exit; // to avoid creating it more than once
fWelcomeMemo := TMemo.Create(Self);
fWelcomeMemo.Parent := Self.MainPanelSourceEditor;
// set any other properties of WelcomeMemo here.
end;
Apart from anything else, this avoids the memo's owner being set to the specific TfrmWelcome instance frmWelcome, which is an accident waiting to happen because it may not be the instance you are actually wanting to work with.
But like #J.. said, you really need to look at a beginner's tutorial if you are blundering around using trial and error the way it sounds like you are.