My program isn't saving/displaying all the bills I've added - ruby-on-rails

Question

I've flirted with learning web dev in the past and haven't had the time as I am a full time Business Student.
I started digging back in today and decided to take a break from the learning and practice what I've learned today by writing a simple program that allows the user to enter in their bills and will eventually calculate how much disposable income they have after their bills are paid each month.
My problem is that the program runs through perfectly, the loop is continuing/exiting when it should, but either the program is not storing the users input in the hash like I'm wanting it to or it's not displaying all the bills entered as it should. Here is my program:
# This program allows you to assign monthly payments
# to their respective bills and will automatically
# calculate how much disposable income you have
# after your bills are paid
# Prompts user to see if they have any bills to enter
puts "Do you have any bills you would like to enter, Yes or No?"
new_bill = gets.chomp.downcase
until new_bill == 'no'
# Creates a hash to store a key/value pair
# of the bill name and the respection payment amount
bills = {}
puts "Enter the bill name: "
bill_name = gets.chomp
puts "How much is this bill?"
pay_amt = gets.chomp
bills[bill_name] = pay_amt
puts "Would you like to add another bill, Yes or No?"
new_bill = gets.chomp.downcase
end
bills.each do |bill_name, pay_amt|
puts "Your #{bill_name} bill is $#{pay_amt}."
end
My questions are:
Is my hash set up properly to store the key/value pairs from the users input?
If not, how can I correct it?
I'm getting only the last bill that was entered by the user. I've tried several bills at a time but only getting the last entry.
As I stated, I'm a noob but I'm extremely ambitious to learn. I've referred to to the ruby docs on hashes to see if there is an error in my code but was able to locate a solution (still finding my way around ruby docs).
Any help is appreciated! Also, if you have any recommendations on ways I can make my code more efficient, could you point me in the direction where I can obtain the appropriate information to do so?
Thank you.
Edit:
The main question has been answered. This is a follow up question to the same program - I'm getting an error message budget_calculator.rb:35:in -': Hash can't be coerced into Float (TypeError)
from budget_calculator.rb:35:in'
From the following code (keep in mind of the program above) -
# Displays the users bills
bills_hash.each {|key,value| puts "Your #{key} bill is $#{value}."}
# Get users net income
puts "What is your net income?"
net_income = gets.chomp.to_f
#Calculates the disposable income of the user
disposable_income = net_income - bills_hash.each {|value| value}
puts disposable_income
I understand the error is appearing from this line of code:
disposable_income = net_income - bills_hash.each {|value| value}
I'm just not understanding why this is unacceptable. I'm trying to subtract all of the values in the hash (pay_amt) from the net income to derive the disposable income.

Answer 1

This is the part that's getting you:
bills = {}
You're resetting the hash every time the program loops. Try declaring bills at the top of the program.
As to your second question about bills_hash, it's not working because the program is attempting to subtract a hash from a float. You've got the right idea, but the way it's set up, it's not going to just subtract each key from the net_income in turn.
The return value of #each is the original hash that you were looping over. You can see this if you open IRB and type
[1,2,3].each {|n| puts n}
The block is evaluated for each element of the list, but the final return value is the original list:
irb(main):007:0> [1,2,3].each {|n| puts n}
1
2
3
=> [1, 2, 3] # FINAL RETURN VALUE
So according to the order of operations, your #each block is iterating, then returning the original bills_hash hash, and then trying to subtract that hash from net_income, which looks like this (assuming my net_income is 1000):
1000 - {rent: 200, video_games: 800}
hence the error.
There are a couple ways you could go about fixing this. One would be to sum all of the values in bills_hash as its own variable, then subtract that from the net_income:
total_expenditures = bills_hash.values.inject(&:+) # sum the values
disposable_income = net_income - total_expenditures
Using the same #inject method, this could also be done in one function call:
disposable_income = bills_hash.values.inject(net_income, :-)
# starting with net_income, subtract each value in turn
See the documentation for Enumerable#inject.
It's a very powerful and useful method to know. But make sure you go back and understand how return values work and why the original setup was raising an exception.