Following script describes the decoding of a JSON Object, that is received via MQTT. In this case, we shall take following JSON Object as an example:
{"00-06-77-2f-37-94":{"publish_topic":"/stations/test","sample_rate":5000}}
After being received and decoded in the handleOnReceive function, the local function saveTable is called up with the decoded object which looks like:
["00-06-77-2f-37-94"] = {
publish_topic = "/stations/test",
sample_rate = 5000
}
The goal of the saveTable function is to go through the table above and assign the values "/stations/test" and 5000 respectively to the variables pubtop and rate. When I however print each of both variables, nil is returned in both cases.
How can I extract the values of this table and save them in mentioned variables?
If i can only save the values "publish_topic = "/stations/test"" and "sample_rate = 5000" at first, would I need to parse these to get the values above and save them, or is there another way?
local pubtop
local rate
local function saveTable(t)
local conversionTable = {}
for k,v in pairs(t) do
if type(v) == "table" then
conversionTable [k] = string.format("%q: {", k)
printTable(v)
print("}")
else
print(string.format("%q:", k) .. v .. ",")
end
end
pubtop = conversionTable[0]
rate = conversionTable[1]
end
local lua_value
local function handleOnReceive(topic, data, _, _)
print("handleOnReceive: topic '" .. topic .. "' message '" .. data .. "'")
print(data)
lua_value = JSON:decode(data)
saveTable(lua_value)
print(pubtop)
print(rate)
end
client:register('OnReceive', handleOnReceive)
previous question to thread: Decode and Parse JSON to Lua
The function I gave you was to recursively print table contents. It was not ment to be modified to get some specific values.
Your modifications do not make any sense. Why would you store that string in conversionTable[k]? You obviously have no idea what you're doing here. No offense but you should learn some basics befor you continue.
I gave you that function so you can print whatever is the result of your json decode.
If you know you get what you expect there is no point in recursively iterating through that table.
Just do it like that
for k,v in pairs(lua_value) do
print(k)
print(v.publish_topic)
print(v.sample_rate)
end
Now read the Lua reference manual and do some beginners tutorials please.
You're wasting a lot of time and resources if you're trying to implement things like that if you do not know how to access the elements of a table. This is like the most basic and important operation in Lua.
Related
I have been using the following Lua code for a while to do simply csv to array conversions, but everything previously had a value in every column, but this time on a csv formatted bank statement there are empty values, which this does not handle.
Here’s an example csv, with debit and credits.
Transaction Date,Transaction Type,Sort Code,Account Number,Transaction Description,Debit Amount,Credit Amount,Balance
05/04/2022,DD,'11-70-79,6033606,Refund,,10.00,159.57
05/04/2022,DEB,'11-70-79,6033606,Henry Ltd,30.00,,149.57
05/04/2022,SO,'11-70-79,6033606,NEIL PARKS,20.00,,179.57
01/04/2022,FPO,'11-70-79,6033606,MORTON GREEN,336.00,,199.57
01/04/2022,DD,'11-70-79,6033606,WORK SALARY,,100.00,435.57
01/04/2022,DD,'11-70-79,6033606,MERE BC,183.63,,535.57
01/04/2022,DD,'11-70-79,6033606,ABC LIFE,54.39,,719.20
I’ve tried different patterns (https://www.lua.org/pil/20.2.html), but none seem to work, I’m beginning to think I can’t fix this via the pattern as it’ll break how it works for the rest? I appreciate it if anyone can share how they would approach this…
local csvfilename = "/mnt/nas/Fireflyiii.csv"
local MATCH_PATTERN = "[^,]+"
local function create_array_from_file(csvfilename)
local file = assert(io.open(csvfilename, "r"))
local arr = {}
for line in file:lines() do
local row = {}
for match in string.gmatch(line, MATCH_PATTERN) do
table.insert(row, match)
end
table.insert(arr, row)
end
return arr
end
I have following JSON data I would like to decode to Lua to access each the publish_topic and sample_rate value.
{"00-06-77-2f-37-94":{"publish_topic":"/stations/test","sample_rate":5000}}
If I understand correctly the Lua table will look like this:
{00-06-77-2f-37-94 = "publish_topic":"/stations/test","sample_rate":5000}
Next I would go through the table to save each value into a local variable.
However, if I try printing out the values of the table (using following code), I get 'nil' as return. Is the code for reading table values wrong?
Does the table have two values or is it just the one: ["publish_topic":"/stations/test","sample_rate":5000] ?
lua_value = JSON:decode(data)
for _,d in pairs(lua_value) do
print(lua_value[d])
end
local topic = lua_value[0]
local timer = lua_value[1]
end
Edit: I am using following JSON library for Lua: http://regex.info/blog/lua/json
Edit2: #Piglet: I implemented your script and modified it by adding a table (conversionTable) in which both elements "publish_topic":"/stations/test" and "sample_rate:5000" would be respectively saved in the variables pubtop and rate. When I however print each of both variables, nil ist returned in both cases.
How can I extract the information out of this table to save in variables?
Ultimately I actually only would like to save the values "/stations/test" and "5000" into these variables. Would I need to parse each of the elements above to get these or is there another way?
local pubtop
local rate
local function printTable(t)
local conversionTable = {}
for k,v in pairs(t) do
if type(v) == "table" then
conversionTable [k] = string.format("%q: {", k)
printTable(v)
print("}")
else
print(string.format("%q:", k) .. v .. ",")
end
end
pubtop = conversionTable[0]
rate = conversionTable[1]
end
local lua_value
local function handleOnReceive(topic, data, _, _)
print("handleOnReceive: topic '" .. topic .. "' message '" .. data .. "'")
-- This sample publishes the received messages to test/topic2
print(data)
lua_value = JSON:decode(data)
printTable(lua_value)
print(pubtop)
print(rate)
end
client:register('OnReceive', handleOnReceive)
I don't know which json library you're using so I can't tell you wether JSON:decode(data) is the correct way.
Assuming lua_value would like like so:
local lua_value = {
["00-06-77-2f-37-94"] = {
publish_topic = "/stations/test",
sample_rate = 5000
}
}
Then your loop
for _,d in pairs(lua_value) do
print(lua_value[d])
end
will indeed print nil.
lua_value has a single element at key "00-06-77-2f-37-94" which is a table.
Each loop iteration will give you a key value pair. So d is actually the value and hence the inner table of lua_value
So you're actually doing this:
local innerTable = lua_value["00-06-77-2f-37-94"]
print(lua_value[innerTable])
Of course lua_value[innerTable] is nil.
Edit:
Try something like
function printTable(t)
for k,v in pairs(t) do
if type(v) == "table" then
print(string.format("%q: {", k))
printTable(v)
print("}")
else
print(string.format("%q:", k) .. v .. ",")
end
end
end
printTable(lua_value)
I have data loaded from JSON and am trying to extract arbitrary nested values using a list as input, where the list corresponds to the names of successive children. I want a function get_value(data,lookup) that returns the value from data by treating each entry in lookup as a nested child.
In the example below, when lookup=['alldata','TimeSeries','rates'], the return value should be [1.3241,1.3233].
json_data = {'alldata':{'name':'CAD/USD','TimeSeries':{'dates':['2018-01-01','2018-01-02'],'rates':[1.3241,1.3233]}}}
def get_value(data,lookup):
res = data
for item in lookup:
res = res[item]
return res
lookup = ['alldata','TimeSeries','rates']
get_value(json_data,lookup)
My example works, but there are two problems:
It's inefficient - In my for loop, I copy the whole TimeSeries object to res, only to then replace it with the rates list. As #Andrej Kesely explained, res is a reference at each iteration, so data isn't being copied.
It's not concise - I was hoping to be able to find a concise (eg one or two line) way of extracting the data using something like list comprehension syntax
If you want one-liner and you are using Python 3.8, you can use assignment expression ("walrus operator"):
json_data = {'alldata':{'name':'CAD/USD','TimeSeries':{'dates':['2018-01-01','2018-01-02'],'rates':[1.3241,1.3233]}}}
def get_value(data,lookup):
return [data:=data[item] for item in lookup][-1]
lookup = ['alldata','TimeSeries','rates']
print( get_value(json_data,lookup) )
Prints:
[1.3241, 1.3233]
I don't think you can do it without a loop, but you could use a reducer here to increase readability.
functools.reduce(dict.get, lookup, json_data)
I know that I can use LIST_TO_ASCI to convert a report to ASCII, but I would like to have a more high level data format like JSON, XML, CSV.
Is there a way to get something that is easier to handle then ASCII?
Here is the report I'd like to convert:
The conversion needs to be executed in ABAP on a result which was executed like this:
SUBMIT <REPORT_NAME> ... EXPORTING LIST TO MEMORY AND RETURN.
You can get access to SUBMIT list in memory like this:
call function 'LIST_FROM_MEMORY'
TABLES
listobject = t_list
EXCEPTIONS
not_found = 1
others = 2.
if sy-subrc <> 0.
message 'Unable to get list from memory' type 'E'.
endif.
call function 'WRITE_LIST'
TABLES
listobject = t_list
EXCEPTIONS
EMPTY_LIST = 1
OTHERS = 2
.
if sy-subrc <> 0.
message 'Unable to write list' type 'E'.
endif.
And the final step of the solution (conversion of result table to JSON) was already answered to you in your question.
I found a solution here: http://zevolving.com/2015/07/salv-table-22-get-data-directly-after-submit/
This is the code:
DATA: lt_outtab TYPE STANDARD TABLE OF alv_t_t2.
FIELD-SYMBOLS: <lt_outtab> like lt_outtab.
DATA lo_data TYPE REF TO data.
" Let know the model
cl_salv_bs_runtime_info=>set(
EXPORTING
display = abap_false
metadata = abap_false
data = abap_true
).
SUBMIT salv_demo_table_simple
AND RETURN.
TRY.
" get data from SALV model
cl_salv_bs_runtime_info=>get_data_ref(
IMPORTING
r_data = lo_data
).
ASSIGN lo_data->* to <lt_outtab>.
BREAK-POINT.
CATCH cx_salv_bs_sc_runtime_info.
ENDTRY.
Big thanks to Sandra Rossi, she gave me the hint to cx_salv_bs_sc_runtime_info.
Related answer: https://stackoverflow.com/a/52834118/633961
I was able to store functions into a table. But now I have no idea of how to invoke them. The final table will have about 100 calls, so if possible, I'd like to invoke them as if in a foreach loop. Thanks!
Here is how the table was defined:
game_level_hints = game_level_hints or {}
game_level_hints.levels = {}
game_level_hints.levels["level0"] = function()
return
{
[on_scene("scene0")] =
{
talk("hint0"),
talk("hint1"),
talk("hint2")
},
[on_scene("scene1")] =
{
talk("hint0"),
talk("hint1"),
talk("hint2")
}
}
end
Aaand the function definitions:
function on_scene(sceneId)
-- some code
return sceneId
end
function talk(areaId)
-- some code
return areaId
end
EDIT:
I modified the functions so they'll have a little more context. Basically, they return strings now. And what I was hoping to happen is that at then end of invoking the functions, I'll have a table (ideally the levels table) containing all these strings.
Short answer: to call a function (reference) stored in an array, you just add (parameters), as you'd normally do:
local function func(a,b,c) return a,b,c end
local a = {myfunc = func}
print(a.myfunc(3,4,5)) -- prints 3,4,5
In fact, you can simplify this to
local a = {myfunc = function(a,b,c) return a,b,c end}
print(a.myfunc(3,4,5)) -- prints 3,4,5
Long answer: You don't describe what your expected results are, but what you wrote is likely not to do what you expect it to do. Take this fragment:
game_level_hints.levels["level0"] = function()
return
{
[on_scene("scene0")] =
{
talk("hint0"),
}
}
end
[This paragraph no longer applies after the question has been updated] You reference on_scene and talk functions, but you don't "store" those functions in the table (since you explicitly referenced them in your question, I presume the question is about these functions). You actually call these functions and store the values they return (they both return nil), so when this fragment is executed, you get "table index is nil" error as you are trying to store nil using nil as the index.
If you want to call the function you stored in game_level_hints.levels["level0"], you just do game_level_hints.levels["level0"]()
Using what you guys answered and commented, I was able to come up with the following code as a solution:
asd = game_level_hints.levels["level0"]()
Now, asd contains the area strings I need. Although ideally, I intended to be able to access the data like:
asd[1][1]
accessing it like:
asd["scene0"][1]
to retrieve the area data would suffice. I'll just have to work around the keys.
Thanks, guys.
It's not really clear what you're trying to do. Inside your anonymous function, you're returning a table that uses on_scene's return value as keys. But your on_scene doesn't return anything. Same thing for talk.
I'm going to assume that you wanted on_scene and talk to get called when invoking each levels in your game_level_hints table.
If so, this is how you can do it:
local maxlevel = 99
for i = 0, maxlevel do
game_level_hints.levels["level" .. i] = function()
on_scene("scene" .. i)
talk("hint" .. i)
end
end
-- ...
for levelname, levelfunc in pairs(game_level_hints.levels) do
levelfunc()
end