How do I determine a variable's data type? How to convert to string?

Question

I have two questions...

Here is a really simple example script which causes an error:

System Events got an error: Can’t make item 1 of every application process whose visible = true into type string.

tell application "System Events"
   repeat with appProc in (every application process whose visible is true)
       display dialog appProc
   end repeat
end tell

1- How do I determine the data type of a variable?

This would be helpful for future reference so I can figure out what kind of data type I am dealing with

2- How do I convert the above data type to a string so it displays with display dialog?

I tried adding:

appProc as string

but then I get another error that says:

Can’t make «class pcap» "myapplication" of application "System Events" into type string.

Answer 1

To get the data type... use class...

set a to "some text variable"
return class of a

Convert to string?... try "as text" or "as string". It mostly works. However in your case appProc has properties (as Red_menace mentioned) and you want to display its name property...

display dialog (name of appProc)