Question

Is there a way to dynamically create arrays in Ruby? For example, let’s say I wanted to loop through an array of books as input by a user:

books = gets.chomp

The user inputs:

"The Great Gatsby, Crime and Punishment, Dracula, Fahrenheit 451,
Pride and Prejudice, Sense and Sensibility, Slaughterhouse-Five, 
The Adventures of Huckleberry Finn"

I turn this into an array:

books_array = books.split(", ")

Now, for each book the user input, I’d like to Ruby to create an array. Pseudo-code to do that:

 x = 0

 books_array.count.times do
    x += 1
    puts "Please input weekly sales of #{books_array[x]} separated by a comma."
    weekly_sales = gets.chomp.split(",")
 end

Obviously this doesn’t work. It would just re-define weekly_sales over and over again. Is there a way to achieve what I’m after, and with each loop of the .times method create a new array?

Answer 1

weekly_sales = {}
puts 'Please enter a list of books'
book_list = gets.chomp
books = book_list.split(',')

books.each do |book|
  puts "Please input weekly sales of #{book} separated by a comma."
  weekly_sales[book] = gets.chomp.split(',') 
end

In ruby, there is a concept of a hash, which is a key/value pair. In this case, weekly_sales is the hash, we are using the book name as the key, and the array as the value.

A small change I made to your code is instead of doing books.count.times to define the loop and then dereference array elements with the counter, each is a much nicer way to iterate through a collection.