Vb6 type mismatch with random number generator

Question

I wanted to generate a random number between 1 and 20 for a game that I am creating and for some reason this code has stopped working and gives me a type mismatch error, I have tried other generators in the game but I get the same error.

Public Counter1 As Integer ' Counters for each reel
Public ArrayImgMid1 As Integer ' Store number to iterate over image arrays
Public ReelPic1 As Variant ' Array of images for each reel
Public Reel1Spin As Long ' Spins for each reel
Public ImgBeth, ImgWallow, ImgDan, ImgChris, ImgCatBug As StdPicture ' Images for reels

Private Sub CmdSpin_Click()

'Enable all timers to imitate spinning
TimerReel1.Enabled = True
TimerReel1.Interval = 100

' Disable spin button
CmdSpin.Enabled = False

' Set all counters to 0
Counter1 = 0

' Generate random number for the first reel to spin
Reel1Num = (CLng(Rnd * 20) + 1) ' This is highlighted when I press debug

Answer 1

Write it like this:

Dim Reel1Num As Long

Reel1Num = (CLng(Rnd * 20) + 1)

Don't use Integer in VB6 - it represents a 16-bit signed integer and it has slightly less performance than Long which is really a 32-bit signed integer. This way you also won't run into limits with the 16-bit data type.

The reason your code doesn't work is because the Int() function doesn't convert the data type of a value to type Integer - it rounds the specified value to an integer value but keeps its data type.

To convert a value to a particular data type, use the CInt(), CLng(), etc. functions. But as I said, avoid using Integer unless you specifically need it - Long is better in most cases.

Edit:

After you posted your code, I can't see a definition of the Reel1Num variable - where is it defined? Is it Reel1Spin? If that's the case, make sure you enable the Require variable declaration option in Tools->Options - it's off by default. If you don't have it on, it's a very easy way to shoot yourself in the foot.

Unrelated to your error, but most of your image objects are defined incorrectly - in VB6, the type of a variable must be specified for every variable, not once per line. So on this line:

Public ImgBeth, ImgWallow, ImgDan, ImgChris, ImgCatBug As StdPicture

you only really create 1 StdPicture object, all others will be variants. The right way to do it is:

Public ImgBeth As StdPicture, ImgWallow As StdPicture, ImgDan As StdPicture, _
    ImgChris As StdPicture, ImgCatBug As StdPicture

Aside from these, I can't see anything wrong with your code - I don't have VB6 installed on my computer. Keep in mind, that VB6 had a funky way of dealing with type mismatch and in some cases the highlighted line may not be the one that causes the actual error. This used to drive me crazy.