Tips and Tricks working with variables in luup code?

Developer's Corner Scene Scripting
#1

I have been doing some basic scripting; if then statements in luup in vera scenes;
One thing that I find incredibly difficult is working and debugging with variables.
Sometimes I will have the code fail due to various different issues; and there is no way to know why things failed (at least I don’t know). I can search the /var/log/cmh/LuaUPnP.log file and get a little bit more information; but if I am writing code that calls a variable; something like:

status5 = luup.variable_get("urn:micasaverde-com:serviceId:Doorlock1", "Status", 59)

I have no way of knowing what the variable “status5” that the system wrote back was… If this was a batch file; I could do something like “echo status5” and have it display the variables so I could know what I was working with… but I can’t seem to find a way to get this information. I’ve tried the “Develop app” section; where it says test luup code; but it just tells me if it failed or not… no details. (perhaps I am using this section wrong?)
How do you guys work with variables and debug? I’m starting to get into some more complex "if elseif else " statements with a lot more variables and it is becoming impossible to know which variable is coming back “nil” or otherwise different than expected.

Any tips for working through this?

#2

Have you tried the print() function, as laid out in the Lua Programming Manual? Seems like it’s intended to send arguments directly to STD_IO, which in Vera’s case, I suspect is the log file. I don’t know how to view variables directly using luup, though. (For stuff like that, I strictly use Expressions in the Reactor plug-in, and let it handle everything.)

See: Programming in Lua : 5.1

#3

Altui and i beleive LuaView have the prin() function.
Else you can write to log or a state variable.

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#4

I indeed think that either ALTUI, Luaview or the old luatest plugin would help you a lot. I personally moved to ALTUI and used the code test feature extensively.

It is rather weird that UI7 offered a test lua code feature with no output or return fields.

#5

I second LuaTest. Easy to invoke and use! Brilliant little utility!!

#6

AltUI also has the facility to pretty-print structured data, which can be incredibly useful…

For example:

print (luup.devices[1])

gives

table: 0xb7db20

but

print (pretty(luup.devices[1]))

shows so much more

{
	 category_num = 19,
	 description = "ZWave",
	 device_num_parent = 0,
	 device_type = "urn:schemas-micasaverde-com:device:ZWaveNetwork:1",
	 embedded = false,
	 hidden = false,
	 id = "",
	 invisible = true,
	 ip = "",
	 mac = "",
	 pass = "",
	 room_num = 0,
	 subcategory_num = 0,
	 udn = "uuid:4d494342-5342-5645-0001-000002b03069",
	 user = ""
}
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#7

Thank you everyone for the tips; Many of these suggestions have advanced me much further along than I was before!

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