Undefined method `-' for nil

Ruby
1

Hi guys.

So I’ve hit a brick wall with a simple piece of code and hope someone
here can shed some light on what’s going wrong …

developer_object_array.each do |dev|
if dev.is_solvent? == false
then puts("#{dev.name} is bankrupt.")
dev.bankrupt = true
bank_object_array.each do |bank|
bank.moves_loans(amount)
else puts("#{dev.name} is not bankrupt.")
end
end

I have the above piece of code in a class. Inside this class I create
and array of Bank and Developer objects. When the code gets to
bank.move_loans
I get an “undefined method `-’ for nil:NilClass (NoMethodError” error.

The move_loans method is defined in the Bank class just does some basic
subtraction on the value passed to it.

I’ve no idea what the error is, as I’ve torn through every piece of code
in the classes and can’t see anything wrong.

Any ideas would be great!! Thanks!

2

On 10/09/2012 09:13 AM, Joz P. wrote:

     bank_object_array.each do |bank|

The move_loans method is defined in the Bank class just does some basic
subtraction on the value passed to it.

I’ve no idea what the error is, as I’ve torn through every piece of code
in the classes and can’t see anything wrong.

Any ideas would be great!! Thanks!

Really need to see what the developer objects and bank objects look
like, and how/ where the bank_object_array gets populated.

Sam

3

class Developer
attr_accessor :name, :networth, :loans, :banks_loaned_from, :bankrupt

def initialize(name, networth, loans, banks_loaned_from, bankrupt)
@name, @networth, @loans, @banks_loaned_from, @bankrupt = name,
networth, loans, banks_loaned_from, bankrupt
end

def is_solvent?
if networth >= owes_amount
then true
else false
end
end

    def owes_amount
total_loans = 0
loans_array = loans.split(',')
loans_array.each { |item| total_loans += item.to_f }
total_loans

end

def owes_bank(bank)
loans_array = loans.split(’,’)
banks_array = banks_loaned_from.split(’,’)
banks_array.each do |item|
if bank == item
then i = banks_array.index(item)
loans_array[i].to_f
else
puts(“No such bank - check name.”)
end
end
end

end

class Bank
attr_accessor :name, :amount_of_deposits, :amount_of_loans

def initialize(name, amount_of_deposits, amount_of_loans)
@name, @amount_of_deposits, @amount_of_loans, = name,
amount_of_deposits, amount_of_loans
end

def moves_loans(amount)
amount_of_loans -= amount
amount_of_deposits += (amount*0.5)
end

def bank_is_solvent?
if amount_of_deposits >= amount_of_loans
true
else
false
end
end

end

require_relative ‘.\Bank.rb’
require_relative ‘.\Developers.rb’

class Bankrupter

creating the developers

L = Developer.new(“L”, 650000, “1500000, 500000, 1000000, 300000”,
“AIB,BOI,Ulster,Anglo”, false)
M = Developer.new(“M”, 2100000, “1400000, 2000000”, “AIB,Anglo”,
false)
R = Developer.new(“R”, 900000, “500000, 700000, 1000000, 1200000”,
“AIB,BOI,RSB,Anglo”, false)
MF = Developer.new(“MF”, 1200000, “400000, 2000000, 8000000”,
“AIB,Ulster,Anglo”, false)
MN = Developer.new(“MN”, 3000000, “100000, 300000”, “BOI,RSB”, false)

creating the banks

AIB = Bank.new(“AIB”, 450, 3000000, 500000, false)
Anglo = Bank.new(“Anglo”, 520, 5000000, 12000000, false)
BOI = Bank.new(“BOI”, 600, 2500000, 2500000, false)
RBS = Bank.new(“RBS”, 530, 2800000, 1700000, false)
Ulster = Bank.new(“Ulster”, 580, 2000000, 1500000, false)

developer_object_array = [ L, M, R, MF, MN]
bank_object_array = [ AIB, Anglo, BOI, RBS, Ulster ]

#Now, test if they are solvent or bankrupt, and then the knock-on
effects for the banks …

developer_object_array.each do |dev|
if dev.is_solvent? == false
then puts("#{dev.name} is bankrupt.")
dev.bankrupt = true
bank_object_array.each do |bank|
bank.moves_loans
end
else puts("#{dev.name} is not bankrupt.")
end
end

end

4

Don’t mind the extra fields in the Bank object creation, they’re not
supposed to be there

5

Go into the function: bank.moves_loans
and for each ‘-’ operation check operand, I am 100 % sure that one of
the operand becomes NIL at some point.

Looking at your question, I would like to give an explicit answer, which
is not expected here:

for each statement involving ‘-’ viz:
a=b-c
replace it by:
if b==nil or c==nil
puts “My 100% is proved, here is the error”
else
a=b-c
end

6

On 10/09/2012 09:35 AM, Joz P. wrote:

   then true

 end

amount_of_deposits, amount_of_loans
else
class Bankrupter
MN = Developer.new(“MN”, 3000000, “100000, 300000”, “BOI,RSB”, false)
bank_object_array = [ AIB, Anglo, BOI, RBS, Ulster ]
end
else puts("#{dev.name} is not bankrupt.")
end
end

end

Well for a start, Bank#moves_loans method takes an ‘amount’ argument
which you don’t appear to be passing. I wouldn’t be assigning your bank
and developer instances to constants either (variable names starting
with upper case letters are implicitly constants in Ruby). Also, the
constructor for the Bank object takes 3 values, however you are passing
them 5?

Sam

7

On 10/09/2012 10:22 AM, Joz P. wrote:

      end

constructor for the Bank object takes 3 values, however you are passing
def move_loans
going on??!!

Sam
It is very confusing what the code actually looks like. Do you think you
could put the whole lot up as a gist on github or some other pastebin
type bizzo? It is not clear where the ‘amount’ value comes from in that
method now for a start =]

Sam

8

Sam D. wrote in post #1079016:

On 10/09/2012 09:35 AM, Joz P. wrote:

   then true

 end

amount_of_deposits, amount_of_loans
else
class Bankrupter
MN = Developer.new(“MN”, 3000000, “100000, 300000”, “BOI,RSB”, false)
bank_object_array = [ AIB, Anglo, BOI, RBS, Ulster ]
end
else puts("#{dev.name} is not bankrupt.")
end
end

end

Well for a start, Bank#moves_loans method takes an ‘amount’ argument
which you don’t appear to be passing. I wouldn’t be assigning your bank
and developer instances to constants either (variable names starting
with upper case letters are implicitly constants in Ruby). Also, the
constructor for the Bank object takes 3 values, however you are passing
them 5?

My bad, I just copied the code wrong … assuming I have all that fixed
…

I’ve stumbled on this:

The move_loans method works if I use this code below as I get the
output:

def move_loans
puts(amount_of_loans - amount)
end

But if I replace the body with what I really want, it throws the error:

def moves_loans
amount_of_loans = amount_of_loans - amount
end

It seems to be THAT body right there that’s throwing the error…what’s
going on??!!

Sam

9

On Mon, Oct 8, 2012 at 11:22 PM, Joz P. [email protected]
wrote:

def moves_loans
amount_of_loans = amount_of_loans - amount
end

Here amount_of_loans is understoos as a local variable, since you have
an assigment, so the amount_of_loans at the right hand side gets
evaluated to nil. I guess you want the instance variable, so:

def moves_loans
@amount_of_loans = @amount_of_loans - amount
end

or

def moves_loans
@amount_of_loans -= amount
end

Jesus.

10

Sam D. wrote in post #1079021:

On 10/09/2012 10:22 AM, Joz P. wrote:

      end

constructor for the Bank object takes 3 values, however you are passing
def move_loans
going on??!!

Sam
It is very confusing what the code actually looks like. Do you think you
could put the whole lot up as a gist on github or some other pastebin
type bizzo? It is not clear where the ‘amount’ value comes from in that
method now for a start =]

Sam

Sorry, I really messed up copying the code :stuck_out_tongue:

The amount gets passed as in:

bank.moves_loans(dev.owes_bank(bank.name))

^^^That’s what should be in Bankrupter class above!