How to loop nested arrays in Ruby - ruby

Question

VERY new to Ruby and coding in general. I'm trying to loop through two dimensional arrays but can't figure it out. Here's what I have:
--Use a loop to print out each person on separate lines with their alter egos.
--Bruce Wayne, a.k.a. Batman
people = [
["Bruce", "Wayne", "Batman"],
["Selina", "Kyle", "Catwoman"],
["Barbara", "Gordon", "Oracle"],
["Terry", "McGinnis", "Batman Beyond"]
]
index = people[0][0]
first_name = people[0][0]
last_name = people[0][1]
hero_name = people[0][2]
4.times do
puts first_name + " " + last_name + "," " " + "a.k.a" " " + hero_name
index = index + 1
end
It does print the first line but then raises an error:
Bruce Wayne, a.k.a Batman
# `+': no implicit conversion of Integer into String (TypeError)

Answer 1

In ruby we don’t use loops by index, like for and family; instead we iterate on collections:
people =
[["Bruce", "Wayne", "Batman"],
["Selina", "Kyle", "Catwoman"],
["Barbara", "Gordon", "Oracle"],
["Terry", "McGinnis", "Batman Beyond"]]
people.each do |first, last, nick|
puts "#{first} #{last}, a.k.a #{nick}"
end
or
people.each do |first_last_nick|
*first_last, nick = first_last_nick
puts [first_last.join(' '), nick].join(', a.k.a ')
end

Answer 2

Your code produces error because you assign a String to index
index = people[0][0]
and then you use it to count with
index = index + 1
You could have used
index = 0
and
index += 1
A more Rubyesque way would be to enumerate the array and print it like this
people.each do |person|
puts "#{person.first} #{person[1]}, a.k.a #{person.last}"
end
Which gives
Bruce Wayne, a.k.a Batman
Selina Kyle, a.k.a Catwoman
Barbara Gordon, a.k.a Oracle
Terry McGinnis, a.k.a Batman Beyond
Storing the parts in a variable improves readability but lenghtens the code which in turn diminishes readability, the choice is yours..
As an alternative you could name the indices or decompose like mudasobwa suggests.
Firstname, Lastname, Nickname = 0, 1, 2
people.each do |person|
puts "#{person[Firstname]} #{person[Lastname]}, a.k.a #{person[Nickname]}"
end

Answer 3

For your code to work:
4.times do |character|
puts people[character][0] + " " + people[character][1] + "," " " + "a.k.a" " " + people[character][2]
end
But iterating in ruby is done as answered by others.
This is a version using a block {} instead:
people = [["Bruce", "Wayne", "Batman"], ["Selina", "Kyle", "Catwoman"], ["Barbara", "Gordon", "Oracle"], ["Terry", "McGinnis", "Batman Beyond"]]
people.each { |character| puts "#{character [0]}, a.k.a #{character [1]} #{character [2]}" }
#=> Bruce, a.k.a Wayne Batman
#=> Selina, a.k.a Kyle Catwoman
#=> Barbara, a.k.a Gordon Oracle
#=> Terry, a.k.a McGinnis Batman Beyond
In general to loop through nested arrays:
people.each do |character|
character.each do |name|
puts name
end
end