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Arrays

Arrays

What makes an array an array

Creating an array

["apple", "banana", "cherry"]

Array Indexes

Array Indexes Exercise

Try this in IRB:

fruits = ["apple", "banana", "cherry"]
fruits[1]

Did you get the result you expected?

Why or why not?

Start At Zero

When counting,

humans start at one,

but computers start at zero.

So the first item in an array is number zero, not number one.

The End

Try this:

fruits[99]

Did you get the result you expected?

Why or why not?

Array Methods

fruits.last
fruits.first
fruits.reverse
fruits.shuffle

Turning an array into a string

fruits.join
fruits.join(" and ")

Note that to_s doesn't work right on arrays:

fruits.to_s
puts fruits.to_s

Looping through an array

fruits.each do |fruit|
  puts fruit
end

Lab: reverse fruit

Given this array:

fruits = ["apple", "banana", "cherry"]

write a program that prints:

yrrehc
ananab
elppa

Setting items in an array

The [] operator works for assignment as well.

fruits[0] = "Apricot"
fruits[1] = "Blueberry"
puts fruits.first

Checking an array

The include? method checks if an object is inside an array or not.

fruits.include? "apple"
true
fruits.include? "pizza"
false

LAB: enemies list refactoring

I'd like you to refactor your old hello.rb program to use the include? method to check if someone is your enemy.

TODO: more array labs