NoMethodError (undefined method `<' for nil:NilClass): - ruby-on-rails

Question

This is the error I have received:
NoMethodError (undefined method `<' for nil:NilClass):
app/controllers/concerns/withdraws/withdrawable.rb:20:in `create'
This is the part of the code in question:
def create
#withdraw = model_kls.new(withdraw_params)
#verified = current_user.id_document_verified?
#local_sum = params[:withdraw][:sum]
if !#local_sum
render text: I18n.t('private.withdraws.create.amount_empty_error'), status: 403
return
end
if !#verified && channel.currency_obj.withdraw_limit < #local_sum <<<<<- Here is the error
render text: I18n.t('private.withdraws.create.unverified_withdraw_limit_error', limit: channel.currency_obj.withdraw_limit), status: 403
return
end
That's all my code:
https://github.com/DigitalCoin1/Spero-Exchange
The error in question is in this file:
https://github.com/DigitalCoin1/Spero-Exchange/blob/rebuild-peatio/app/controllers/concerns/withdraws/withdrawable.rb
Thank you very much!!!

Answer 1

Remember, (almost) everything is Ruby is an object... including nil.
Keeping that in mind, consider what happens when you call a method that doesn't exist on nil:
irb(main):001:0> nil.something
Traceback (most recent call last):
2: from /Users/scott/.rbenv/versions/2.5.1/bin/irb:11:in `<main>'
1: from (irb):1
NoMethodError (undefined method `something' for nil:NilClass)
Additionally, in Ruby operators such as >, <, and == are actually method calls. So, for example, an instance of Integer such as 3 has a method defined on it called < and when you call 3 < 4, that calls the method on that instance. This works like that because in Ruby you can omit parentheses when making method calls. For example:
irb(main):001:0> 3 < 4
=> true
irb(main):002:0> 3.<(4)
=> true
So putting these two examples together:
irb(main):014:0> nil < 4
Traceback (most recent call last):
2: from /Users/scott/.rbenv/versions/2.5.1/bin/irb:11:in `<main>'
1: from (irb):14
NoMethodError (undefined method `<' for nil:NilClass)
Now, let's take a look at your code.
You're getting the exception:
NoMethodError (undefined method `<' for nil:NilClass)
On this line:
!#verified && channel.currency_obj.withdraw_limit < #local_sum
Looking at this code, you are only calling < in one place. This means that whatever is to the left of it (channel.currency_obj.withdraw_limit) must be nil.
There are a few ways we can fix this... The best way, (in my opinion) is to make sure that channel.currency_obj can never be nil. I unfortunately don't have enough code to show you exactly how to do that, so let's look at some other options...
We can use Ruby 2.3+'s safe navigation operator (&.) -- but it's a little weird to use with an operator like <.
channel.currency_obj.withdraw_limit&. < #local_sum
Note: in this example the expression will evaluate to nil and because nil is falsey the conditional will return false.
Or, we can just add another expression to our conditional to check for nil:
!#verified && channel.currency_obj.withdraw_limit && channel.currency_obj.withdraw_limit < #local_sum

Answer 2

The error happened when channel.currency_obj.withdraw_limit return nil or #local_sum is nil.
And it can't compare nil value.
You must check #local_sum again, and make sure that it have a value. Or channel.currency_obj.withdraw_limit make sure that it have a value.
But i guess that channel.currency_obj.withdraw_limit return nil.
That your problem.

Answer 3

NoMethodError (undefined method `<' for nil:NilClass):
app/controllers/concerns/withdraws/withdrawable.rb:20:in `create'
This error denotes that it is trying to compare < for a nil value.
Can you please print and check channel.currency_obj.withdraw_limit and #local_sum before the error statement.
To avoid nil errors you can include nil check.
if channel.currency_obj.withdraw_limit != nil and #local_sum != nil