Check if a channel object variable exists

[Simon_Aldworth]

Hi,

How do I check if a channel object variable was successfully set?

Early in my code I use the following to determine if a channel exists and, if so, to set a channel object variable to represent it:

If Data.Root.ChannelGroups(1).Channels.Exists("Yaw Rate Gain") Then
  Set YRateG = Data.GetChannel("Yaw Rate Gain")
End If

Later in my code I'd like to check if YRateG is valid but I can't find a way of checking without tripping an error if it isn't.

I've tried using IsNull on YRateG.Name and I've tried Data.Root.ChannelGroups(1).Channels.Exists(YRateG.Name), but neither worked.

Thanks, Simon.

[Brad_Turpin · Accepted solution]

Hi Simon,

I'd recommend you use the IsObject(YRateG) comparison.  As long as you don't initialize the variable to Nothing or re-use it between the Set assignment and when you compare, this should work.

Brad Turpin

Principal Technical Support Engineer

National Instruments

[AndreasK]

dim YRateG : Set YRateG = nothing
If Data.Root.ChannelGroups(1).Channels.Exists("Yaw Rate Gain") Then
  Set YRateG = Data.GetChannel("Yaw Rate Gain")
End If

if not YRateG is nothing then
end if

could be an alternative.

Be aware that isobject will also return true for nothing.