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Conditional use

Posted on 2002-07-03
Medium Priority
Last Modified: 2011-10-03

I have a flag in the registry called "ShowOptions" that can be "YES" or "NO". In the Main.pas unit of my project, I want to load (or use) another unit called "UOptions.pas" depending of the value in the the registry. I want that because the unit "UOptions.pas" refers to some DLL and these files are not necessarly on the client machine.

How can I do that ????
Question by:roioep
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Expert Comment

ID: 7127666
Instead of linking to the DLLs statically (function ... external ...), you should load the DLL dynamically at runtime, using LoadLibrary, GetProcAddress, FreeLibrary.

Author Comment

ID: 7127779
"UOptions" is a frame with controls. The form "UMain.pas" contains the UOptions frame. This frame use a lot of dll. I don't want to "use" the frame if the registry key says "NO".

Author Comment

ID: 7127790
What I want is to be able to use or not a unit and its components at runtime...
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Expert Comment

ID: 7127817
Let's clarify one point: You don't want to use the frame because the DLLs used by the frame may not be present on the target system.
So your real problem is the DLLs, not the frame.

The only way to conditionaly use a unit is to compile it into a runtime package which would be loaded or not dynamically at runtime. This may introduce you to a whole new set of problems, especially if you haven't done it before.

Why not attack the root of the problem? Redesign the frame unit so that it does not link the DLLs statically but loads them dynamically at runtime...
Just my 2c, of course.
LVL 14

Expert Comment

ID: 7129217
TOndrej, you always say it's only your 2c, but you always give very useful 2c... :)
LVL 34

Expert Comment

ID: 7130935
hello roloep, I may not compleatly understand your problem, but it seems like you do not want the Frame to be present if the boolean is False in the registry. Since a Frame is like a Form you might try this, click on the frame and then click "Delete" in the Edit menu, to remove it from your main form. You can look in the Project Menu "Options" an see on the 'Forms" Tab that the Main Form "Form1" is in "Auto-Create" side and the "Frame1" is on the "Availible" forms side. Now in your Main Forms OnCreate Event add this code

procedure TForm1.FormCreate(Sender: TObject);
{get the ShowOptions value}
if ShowOptions then
  Application.CreateForm(TFrame1, UOptions);
  UOptions.Parent := Self;
  UOptions.Visible := True;
  UOptions.Top := 88;
  UOptions.Left := 488;
  //UOptions.Color := clRed;
  {add any start up code here}

this will load your Form without the Frame if ShowOptions is False and the UOptions.pas won't be executed

Expert Comment

ID: 9343112
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Expert Comment

by:Lukasz Lach
ID: 9460048
No comment has been added lately (18 days), so it's time to clean up this TA.
I will leave a recommendation in the Cleanup topic area for this question:


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Accepted Solution

YensidMod earned 0 total points
ID: 9534299
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