Building a Net Income Calculator Application Using Ruby

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This tutorial is for beginners who want to learn how to build applications in Ruby programming language.

What will we build?

We will build a net income calculator for freelancers in an imaginary company that serves as a middleman between a freelancer and an employer. To be able to focus on Ruby, we won’t build a web based application so you won’t have to use HTML. What we will build is a very simple command line application.

Requirements

• The user should be able to input his/her hourly rate.
• The user should also be able to input the number of hours he/she worked.
• We will assume that our imaginary company deducts $1 + 10% of the gross income of the user .
• The gross income, net income and deductions should be shown to the user.

Building the command line application

Create a file and name it income_calculator.rb

Before starting to write code, it’s a good practice to plan how you will build the application first. Let’s do that by adding comments in income_calculator.rb

# ask the hourly rate of the user
# convert hourly rate to float
# ask the number of hours that the user has worked
# convert hours worked to float
# multiply the hourly rate and the number of hours worked
# get the 10% of the gross income
# add 1 to the deduction
# subtract the deductions to the gross income
# show the gross income, net income and deductions to the user

Now that we have a clear idea on what are the steps that we should code to achieve the expected result, let’s start writing code.

# ask the hourly rate of the user
print “What is your hourly rate?”
hourly_rate = gets

gets is a built-in function in Ruby that we can use to gather inputs from a user. What this block of code basically does is ask the hourly rate of the user and stores the input of the user in the hourly_rate variable.

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# convert hourly rate to float
hourly_rate = hourly_rate.to_f

The result of gets is a string so we are converting it to a float for us to be able to use it for math operations later.

# ask the number of hours that the user has worked
print “How many hours did you worked?”
hours_worked = gets
# convert hours worked to float
hours_worked = hours_worked.to_f

What the code above does is similar to the code that I’ve discussed earlier. It just asks the number of hours that the user worked, store it in the hours_worked variable then converts it to a float.

# multiply the hourly rate and the number of hours worked
gross_income = hourly_rate * hours_worked

To get the gross income of the user, we are multiplying the user’s hourly rate and the number of hours worked. We are storing the result in the gross_income variable.

# get the 10% of the gross income
deduction = gross_income * .10

We are multiplying gross income and 0.10 to get the 10% of gross income. We are storing the result in the deduction variable.

# add 1 to the deduction
total_deductions = deduction + 1

Since the company also deducts $1 to the gross income of the user, we are adding 1 to the value of deduction variable and we are storing the result to total_deductions variable.

# subtract the deductions to the gross income
net_income = gross_income — total_deductions

To compute the net income of the user, we are subtracting the total deductions to the gross income.

# show the gross income, net income and deductions to the user
puts “Gross income: “ + gross_income.to_s
puts “Net income: “ + net_income.to_s
puts “Total deductions: “ + total_deductions.to_s

This block of code exactly does what the comment says. It will show the gross income, net income and deductions to the user. In Ruby, since we can’t concatenate a string (Example: “Gross income”) and a float (gross_income), we have to convert gross_income to a string. We can convert a float to a string by using the to_s method.

The contents of income_calculator.rb should now look like this:

# ask the hourly rate of the user
print “What is your hourly rate?”
hourly_rate = gets
# convert hourly rate to float
hourly_rate = hourly_rate.to_f
# ask the number of hours that the user has worked
print “How many hours did you worked?”
hours_worked = gets
# convert hours worked to float
hours_worked = hours_worked.to_f
# multiply the hourly rate and the number of hours worked
gross_income = hourly_rate * hours_worked
# get the 10% of the gross income
deduction = gross_income * 0.10
# add 1 to the deduction
total_deductions = deduction + 1
# subtract the deductions to the gross income
net_income = gross_income — total_deductions
# show the gross income, net income and deductions to the user
puts “Gross income: “ + gross_income.to_s
puts “Net income: “ + net_income.to_s
puts “Total deductions: “ + total_deductions.to_s

Now let’s run our command line application by running this command in your terminal:

ruby income_calculator.rb

It should ask your hourly rate and number of hours worked then show your gross income, net income and total deductions.

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