Make the uninstall registry key conditional via code

Question

How do you make Inno Setup disable CreateUninstallRegKey via code?

My setup.exe file created in Inno Setup accepts parameters, e.g.:

setup.exe -a

or

setup.exe -b

If -a parameter is supplied, then enable CreateUninstallRegKey, or if -b parameter is supplied, then disable CreateUninstallRegKey.

Is there anyway to set CreateUninstallRegKey via code or do I have to make a function then call the function in script section?

This help page explains about using {code:...} constants, but unfortunately I got this error:

Thanks

Answer 1

Do not use the {code:} expression for passing values to Boolean type directives. Do it this way:

[Setup]
AppName=My Program
AppVersion=1.5
DefaultDirName={pf}\My Program
CreateUninstallRegKey=NeedsUninstallRegKey

[Code]
function CmdLineParamExists(const Value: string): Boolean;
var
  I: Integer;  
begin
  Result := False;
  for I := 1 to ParamCount do
    if CompareText(ParamStr(I), Value) = 0 then
    begin
      Result := True;
      Exit;
    end;
end;

function NeedsUninstallRegKey: Boolean;
begin
  Result := CmdLineParamExists('-a');
end;