Undifined method '[]' for nil:NilClass <NoMethodError>

Hello,

I am completely new to Ruby and thus I am not quit sure how to
troubleshoot this issue. I have looked at other forums and found nothing
that helps my particular situation.

I am trying to count the number of “Chicken Sandwich” products sold each
week for 8 weeks starting 1/4/2015 - 1/10/2015.

I have successfully run this code when I only attempt one week (so the
same script except lines 23,34,35,36) but as soon as I introduce a while
loop to go over the 8 weeks, or create a different function for each
week I get the same error. It seems that after I use the code in lines
29-33 once I can’t use it again in the same script, even if I change the
array name (item_arrey) and change the parsed JSON data object name
(items_js) across different functions.

For this script, the error occurs in line 29 in ‘fetch_lto_info’:
undefined method ‘[]’ for nil:NilClass from line 40 in
‘’

Any advice would be awesome remember though, I’m a noob. Thanks.

Sergio Vaca wrote in post #1170831:

Watching lto_week array i see :

def fetch_lto_info(location_id)

lto_week = []
week_num = 1

loop { lto_week[week_num] += … }

week_num += 1
end
return lto_week[1],lto_week[2],lto_week[3],lto_week[4],
lto_week[5],lto_week[6],lto_week[7],lto_week[8]
end

you should initialize lto_week with 8 zeros in place of a empty array:
lto_week=[0]*8

Thanks raubarede, but I’m still getting the same error on line 29…

======
29 items_js[“Data”][“SalesDetails”].each do |item_arrey|
30 if item_arrey[“Title”] == “Chicken Sandwich”
31 lto_week[week_num] += item_arrey[“ItemCount”]
32 end
33 end

for a couple of the weeks the array items_js[“Data”][“SalesDetails”] may
be empty (i.e. []). So that may be causing the error but I’m not quite
sure how to get around that.

Sergio Vaca wrote in post #1170962:

Thanks raubarede, but I’m still getting the same error on line 29…

======
29 items_js[“Data”][“SalesDetails”].each do |item_arrey|
30 if item_arrey[“Title”] == “Chicken Sandwich”
31 lto_week[week_num] += item_arrey[“ItemCount”]
32 end
33 end

for a couple of the weeks the array items_js[“Data”][“SalesDetails”] may
be empty (i.e. []). So that may be causing the error but I’m not quite
sure how to get around that.

the <<undefined method ‘[]’ for nil:NilClass>> error mean
that you apply [] on a data which is nil.

if you apply [] on a empty array (or a hash whch has not the key)
, you get nil (without error):
{a: 1}[‘a’] >> 1
{b: 1}[‘a’] >> nil
nil[0] >> undefined method ‘[]’ for ni…

On this context, i think that ‘items_js’ has no field ‘Data’ ,
so items_js[“Data”] give nil , then nil[“SalesDetails”] give
your error.

try
if items_js[“Data”] && items_js[“Data”][“SalesDetails”]
items_js[“Data”][“SalesDetails”].each {…}
end

Perhaps, a more rubyst code can be

if items_js[‘Data’] && items_js[‘Data’][“SalesDetails”]

sum = items_js[‘Data’][‘SalesDetails’].select {|a|
a[‘Title’] == “Chicken Sandwich”
}.map {|a| a[“ItemCount”]}.compact.inject(&:+)

lto_week[week_num] += sum
end

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