[gmarco]

Originally Posted by Phanx That's because you're doing it wrong. Here's what your code is currently doing: mounts = {} category="new_category" mount="Swift Moonsaber" The first line creates the table { } and assigns it to the variable "mounts". The second line creates the string "new_category" and assigns it to the variable "category". The third line creates the string "Swift Moonsaber" and assigns it to the variable "mount". Now when you do: mounts[category][mount]=true This is what's happening: The code looks for a table under the variable name "mounts". This returns the table, {}. The code looks for the value under the variable name "category" as a table key. This returns nil, because the "mounts" table is empty. The code looks for the value under the table returned by "mounts[category]". This fails and throws an error, because "mounts[category]" is nil, not a table. What you need to do is: local mounts = {} local category = "new_category" local mount = "Swift Moonsaber" mounts[category] = {} Then you can add values to the category the way you were trying to: mounts[category][mount] = true

Thanks Phanx,
I think I have finally understood :-)

On a side note, you should never create global variables with such generic names as "mounts" and "category" and "mount"...

Yes I know,
the above code was only a pseudo code I wrote to show the problem.
In the addon I surely use local for my names. :-)

Btw thanks for the great explanation on how the global var impact in the addon dataspace.

Now I an continue the rewrote :-)