How would I go about saving the state of a script such that it can be recalled the next time the script is run?
Is there a mechanism (short of immediately writing all parameter changes to disk as soon as they happen) that will ensure state is saved when a script is closed?
One option would be to store all the data youād like to recall in parameters. Then itās just saving and loading a pset. You can save a pset with params:write(), and load a pset with params:read(). Youāll need a params:bang() after reading.
Another option would be to write the data to a file on script close, and read it back in on script init.
I did this in foulplay, way down at the bottom.
Cool, thanks @Justmat. Are there advantages and disadvantages to each approach?
I canāt seem to find anything on ParamSet beyond the reference page which doesnāt provide much in the way of context.
i think that it depends on the complexity of a script and how you want to manage it. with the new hide and add_group functions, you can definitely (for example) break out all the steps in a sequence as parameters that the user wonāt ever see, but will collect with PSET creation. super straightforward for the user and depending on your scripting style, can really help with variable management.
for scripts that have many tables of information that your user will want to persist across sessions, i think external files are primo. @Justmatās example is a great starting point 
for cheat codes, i handle saving/restoring 100ās of variables within ācollectionsā ā savestate and loadstate functions that grab data from parameters, variables, filepaths, etc. this breaks the user experience a bit, though ā a user needs to use the ācollectionsā function to save things rather than relying on the system PSET.
i do wonder if there isnāt a way to execute a custom savestate function as a callback to creating a PSET, tho. that feels like itād offer the best flexibility.
Thanks @dan_derks thatās useful. So ParamSet is there so that script authors and users can create their own presets for your scripts?
My current (first) script is pretty simple, at the moment, so Iām not sure it really needs preset save and recall, so maybe just dumping the current state to a file in /lib would suffice.
On the other hand, Iād like to know how to do presets, too.
paramset provides a few things:
param:get and param:set are super useful!)more on presets + MAP from a āplayā standpoint here: https://monome.org/docs/norns/play/#pset
Ah, that does sound pretty useful. I will definitely look into using ParamSet, then, as I do want to make params mappable to MIDI controllers.
sounds good!
icymi, hereās the section of norns study 3 that introduces best practices for param handling: https://monome.org/docs/norns/study-3/#parameters
Great, I will look at that! I must admit, I skipped the Studies. Will have to go back to them. Thank you for reminding me.
Iām a bit confusedā¦
Iāve managed to add various params, but Iām confused about the order I should do things in. This is what I have currently in my init() function:
function init()
-- Params
params:add_control("tempo","tempo",controlspec.new(40,200,'lin',0,110,'bpm'))
params:set_action("tempo", function(t) clk:bpm_change(t) end)
params:add_control("xpos","xpos",controlspec.new(1,5,'lin',0,3))
params:set_action("xpos", function(x) patterngen.set_xy(x, params:get('ypos')) end)
params:add_control("ypos","ypos",controlspec.new(1,5,'lin',0,3))
params:set_action("ypos", function(y) patterngen.set_xy(params:get('xpos'),y) end)
params:read("luagridstate.pset")
params:bang()
metro_save = metro.init(function(stage) params:write("luagridstate.pset") end, 10)
metro_save:start()
-- OTHER STUFF
end
But I get
pset >> write: luagridstate.pset
pset: BAD FILENAME
every time metro attempts to save the pset.
searching in the norns lua stack reveals some clues
--- write to disk.
-- @param filename either an absolute path, a number (to write [scriptname]-[number].pset to local data folder) or nil (to write default [scriptname].pset to local data folder)
-- @tparam string name
function ParamSet:write(filename, name)
filename = filename or 1
if type(filename) == "number" then
local n = filename
filename = norns.state.data .. norns.state.shortname
filename = filename .. "-" .. string.format("%02d",n) .. ".pset"
end
print("pset >> write: "..filename)
local fd = io.open(filename, "w+")
if fd then
io.output(fd)
if name then io.write("-- "..name.."\n") end
for _,param in pairs(self.params) do
if param.id and param.save and param.t ~= self.tTRIGGER then
io.write(string.format("%s: %s\n", quote(param.id), param:get()))
end
end
io.close(fd)
else print("pset: BAD FILENAME") end
end
same clue is revealed by API doc for paramset.write
http://monome.org/norns/classes/paramset.html#ParamSet:write
Study 3 should probably be updated, as it doesnāt work as described, in that case.
With
function init()
-- Params
params:add_control("tempo","tempo",controlspec.new(40,200,'lin',0,110,'bpm'))
params:set_action( "tempo", function(t) clk:bpm_change(t) end)
params:add_control("xpos","xpos",controlspec.new(1,5,'lin',0,3))
params:set_action( "xpos", function(x) patterngen.set_xpos(x) end)
params:add_control("ypos","ypos",controlspec.new(1,5,'lin',0,3))
params:set_action( "ypos", function(y) patterngen.set_ypos(y) end)
params:add_control("density_kick","density_kick",controlspec.new(0,1,'lin',0,0.5))
params:set_action( "density_kick", function(x) patterngen.set_threshold_kick(x) end)
params:add_control("density_snare","density_snare",controlspec.new(0,1,'lin',0,0.5))
params:set_action( "density_snare", function(x) patterngen.set_threshold_snare(x) end)
params:add_control("density_hat","density_hat",controlspec.new(0,1,'lin',0,0.5))
params:set_action( "density_hat", function(x) patterngen.set_threshold_hat(x) end)
params:read(nil)
params:bang()
metro_save = metro.init(function(stage) params:write(nil) end, 10)
metro_save:start()
---etc.
end
I now get
pset >> write: /home/we/dust/data/luagrid/luagrid-01.pset
The preset seems to contain the value I expect, after running the script and tweaking params.
However, while tempo seems to be currently recalled, when re-running the script, the value for āxposā and āyposā always get their default values, rather than those previously written to the pset (and these values are re-written into the pset the first time it auto-saves, assuming I havenāt changed them manually at this point).
UPDATE
My bad- a āreset()ā function was being called later on in init(), that was resetting the xpos and ypos params.
Removed that, and all appears to be working as expected, now!
I came here looking for the right syntax to pass to params:write. What I came away with, from searching the norns scripts installed on mine was:
params:write(_path.data .. "myscript/myfile.pset","pset-name")
Another thing Iāve noticed, and I might be wrong here, but it seems that itās much more efficient to put your pset save in the cleanup function, rather than in a clock or metro. I put together a little āautosaveā example for myself which works that way:
init = function ()
-- set up params first
params:add_number("numtest", "numtest", 5)
-- load latest autosave values
params:read(_path.data .. "myscript/autosave.pset")
end
cleanup = function ()
-- save params before unloading
params:write(_path.data .. "myscript/autosave.pset","autosave")
end
I kind of like it, because you can still save out psets manually to āsnapshotā the current state. then if you were to load that pset, itās what would be saved to the autosave state at cleanup.
Edit: One thing I misjudged, if you save a pset through the pset menu, the script is now set to use that pset next time you load, which makes my loading of autosave there not work.