Writing to the song comments

Renoise Tool Development
1

Writing to the song comments would be nice. I just spend an hour or so starting to implement a tool for per track comments until I realized that I cannot write in the song comments!

2

Yes you can?

  
-- Song Comments  
renoise.song().artist, _observable  
 -> [string]  
renoise.song().name, _observable  
 -> [string]  
renoise.song().comments[], _observable  
 -> [array of strings]

From: Renoise.Song.API.lua

3

Doesn’t work for me, I can only read. When I write something in there, no changes are visible, the array is still the same.

4

This works fine:
local songcomments = {“This is my new songcomment”, “and now it is empty”}
renoise.song().comments = songcomments

If a similar construction doesn’t work for you, try to make your songcomment array a global variable in the header of your lua-file before adding contents to it.
Usually this is a variable scope issue in Lua and is a pitfall for many.

5

Ah, so I cannot just write in the renoise.song().comments[] array directly, I have to copy it into a new array, modify that and then set the renoise.song().comments to the new one?

6

Yeah, that is strange.

I would have expected

renoise.song().comments[1] = “Hello”
renoise.song().comments[2] = “World”

To work?

7

No that doesn’t work, similar like the song.pos and song.line thing, these have to be ported to a local created variable first, adjusted and then the whole variable has to be given back to the songpos key. So Fladd’s assumption is correct here.

8

SongPos is an object.

renoise.song().comments is an “Array”.

There’s a big difference. Example:

  
local my_array = { }  
my_array[1] = "Hello"  
my_array[2] = "World"  
rprint(my_array)

Vs:

  
oprint(renoise.SongPos())

This is a bug IMHO.

9

All property tables of basic types (strings, numbers, booleans) in the API are temp copies and not references. This is indeed not very comfortable and not obvious, but I could not find a clever way to deal with this in general in the LUA API backend. So I can’t simply “fix” this - sorry.

10

OK, thanks for the explanation.

I guess that should be documented. I’ll try to add it later today.