Refactoring long methods, a simple example in ruby

In this article, I would like to show how to refactor long methods in ruby.

Let’s say we have such a method with a long line hard to understand code.

def total 
  amount + (amount * TAX) — (amount * (discount_percentage / 100.0))      +(amount * (tip_percentage / 100.0))
end

What is the best way to refactor this method?
I think you should start by breaking the long code into parts and come up with a variable name for each part.

def total
 tax = amount * TAX
 discount = amount * (discount_percentage / 100.0)
 tip = amount * (tip_percentage / 100.0)
 amount + tax — discount + tip
end

Looks much better than the original, doesn’t it?
Now let’s think about what we can improve further, we can now replace each variable with the query method.

Converting these variables to methods can greatly simplify this code and will also make them reusable.

def total 
 amount + tax — discount + tip
end
def tax
 amount * TAX
end
def discount
 amount * (discount_percentage / 100.0)
end
def tip
 amount * (tip_percentage / 100.0)
end