Is there documentation for instance_name anywhere?

[a_w]

I would like to set my instance name to be the value of a required drop down, is this possible?

The example xslx has this data

instance_name_example

concat(${lname}, '-', ${fname}, '-', uuid())
where lname and fname are required text boxes.

however when I try and put my dropdowns name I get an error in Collect. I set the value in Build Settings -> form properties
and pasting in my code concat(${observer_select})

when I export to xml and move (using adb) onto my phone when I try and enter the data I get this error...

I get the same error (in fact this error message is from) if I use a simple text element also.
Both the drop down and the text box are required.

The only documentation I have found is this
http://xlsform.org/#instance-name

[LN]

The concat function is used to glue ("concatenate") multiple pieces of text together. It needs more than one value to work. I think in your case you just want ${observer_select} as the instance name.

[a_w]

I tried removing the function and that still fails with the same error. I left it in as I will, in reality, want to concat a couple of things to get a unique survey name.

A link to a simple (required) textbox also fails with the same error

I thank you SO much for taking time to trying to help me. If it helps the survey is here and maybe you can see if I am doing something silly!

OrangServ/OpenDataKit/Simple Survey at master · fo-am/OrangServ

Aidan