Can two nil values be compared from a table?

[mdxafx]

Hi all,

was on the forum last night finding out why my Eject if no
cd in drive functions would not work. My new problem is
that if there is a Cd in one of the drive then don't eject the other
one.

The only trouble is that Drive.GetInformation will return a nil value
when looking at an emtpy CD-Rom Drive, but thats fine!

How would i go about comparing to see if both drives == nil!

Here the code:



tDrives = Drive.Enumerate();
for index in tDrives do
nDriveType = Drive.GetType(tDrives[index]);

if nDriveType == 5 then

tDriveInformation = Drive.GetInformation(tDrives[index]);

if tDriveInformation == nil and nil then -- it works with one (nil) but ejects
-- The other drive, i need them to
-- be both empty before ejecting!

Drive.Eject(tDrives[index]);


else

Dialog.Message("Disc in Drive", "A disc in 1 of the Drives", MB_OK, MB_ICONINFORMATION, MB_DEFBUTTON1);



end
end
end



i thought the : nil and nil - would be good comparison, but it dosen't work.

As always, Thanks in advanced for looking!

mdxafx.

[Roboblue]

I don't know how to get it using the AMS Drive actions (I'll have to look at it).
But, using Worms Drive Serial dll, this will eject any drive NOT having a disc in it. Just put the dll in the path shown in the code.

--- get the drives on the system
	tblDrives = Drive.Enumerate();
	--- walk the table to process each drive
	for n, DriveLetter in tblDrives do
	---Get the drive type
	nType = Drive.GetType(DriveLetter)
	--- if the type equals 5 (Fixed), get it's Label, and Serial
		if nType == String.ToNumber(5) then
		sSerial = DLL.CallFunction("AutoPlay\\Docs\\dll\\DriverSer.dll", "DriveSerialNumber", "\""..DriveLetter.."\"", DLL_RETURN_TYPE_STRING, DLL_CALL_STDCALL)
		sEject = ""..DriveLetter..""..sSerial..""
		sFound = String.Find(sEject, "ERROR", 1, true);
			if sFound ~= -1 then
			Drive.Eject(sEject);
			end
		end
	end

[mdxafx]

Thats what my code does anyway, eject the drive which has
no disk in it.

what: Get.DriveInformation does is return a NIL value if there is
no disc in the drive.

what im trying to is see if both drive == NIL before ejecting them!
If only one drive == Nil there is a disc in one of the drive, therefore
do not eject any drive!

Thanks for the reply!

Hope someone can help me get the problem solved!

[Buffman]

Hi mdxafx,

This is what I'd do in this situation. Let me know how this works out for you.

nFullDrive = 0; --Start out by declaring all CDROMS are empty
tDrives = Drive.Enumerate();
for index in tDrives do
     nDriveType = Drive.GetType(tDrives[index]);
     if nDriveType == 5 then
          tDriveInformation = Drive.GetInformation(tDrives[index]);
          if tDriveInformation ~= nil --Here look for a drive that has a disc in it
               nFullDrives = nFullDrive+1;
          end
     end
end
if nFullDrive == 0 then
     Drive.Eject(tDrives[index]);
else
     Dialog.Message("Disc in Drive", "A disc in 1 of the Drives", MB_OK, MB_ICONINFORMATION, MB_DEFBUTTON1);
end

I haven't tested the code, but the idea should work. It's late and I tend to make a lot of coding mistakes late at night. =)

[bule]

Just for the hint, nil is not equal to another nil.

[mdxafx]

Buffman: i corrected the errors and typo's in your code :



nFullDrive = 0; --Start out by declaring all CDROMS are empty
tDrives = Drive.Enumerate();
for index in tDrives do
nDriveType = Drive.GetType(tDrives[index]);
if nDriveType == 5 then
tDriveInformation = Drive.GetInformation(tDrives[index]);
if tDriveInformation ~= nil then -- (then) was missing!
nFullDrive = nFullDrive+1; -- was: nFullDrives = nFullDrive+1;
end
end
end
if nFullDrive == 0 then
Drive.Eject(tDrives[index]);
else
Dialog.Message("Disc in Drive", "A disc in 1 of the Drives", MB_OK, MB_ICONINFORMATION, MB_DEFBUTTON1);
end


Correct me: -

but this code does not work because the three end statements closes
the argument therefore the : Drive.Eject(tDrives[index]);
returns: can't find string!

If you put:

if nFullDrive == 0 then
Drive.Eject(tDrives[index]);
else
Dialog.Message("Disc in Drive", "A disc in 1 of the Drives", MB_OK, MB_ICONINFORMATION, MB_DEFBUTTON1);
end

before the three end statements you get
1 drive opens
1 stays closed (if you have 2 drive, 1 with a disc in it!).

Im going to look at this in more depth!

Any suggestion in the mean while of how this could be done would
be helpful!

Thanks to all!