Now that we've practiced reading arrays, we will look at how to edit them and add to them.

It's broken! Run learn or rspec in your terminal. I'm not sure what happened, but the colors of the rainbow are wrong! Right now, our rainbow is an array with the following colors:

rainbow_colors = [
  "yellow",
  "default",
  "light_cyan"
]

When we run our tests, these colors are printed out in order using a Ruby gem, colorize. Our goal is to change this array so that it becomes "red", "light_red", "light_yellow", "green", and "blue". When printed, this will get us the closest to a completed rainbow we can get in our terminal.

In an array of values like rainbow_colors, each value can be thought of as its own variable. We can do something like this in Ruby:

my_variable = 1
puts my_variable # outputs 1
my_variable = "hello"
puts my_variable # outputs "hello"

And similarly, we can change values within an array too:

my_array[0] = 1
puts my_array[0] # outputs 1
my_array[0] = "hello"
puts my_array[0] # outputs "hello", the new value for my_array[0]

With this ability, we can start to fix our rainbow by rewriting the individual values in the array.

In the file editing_arrays.rb, write a solution for the method change_rainbow_colors that changes the current three values, "yellow", "default", and "light_cyan" to the correct colors "red", "light_red", "light_yellow". Use the index of these values to make changes.

You should see the rainbow change to these colors when running tests.

So far so good. We can use the index to modify existing values, but we're still short a few colors, and need to add "green" and "blue".

We could use index values to do this too. So for example, something like:

my_array = ["a","b","c","d","e"]
my_array[5] = "f"
my_array # returns ["a","b","c","d","e","f"]

However, we would need to always keep track of how big the array is in order to use indexes. Fortunately, arrays have a built in method to take care of this, push:

my_array = ["a","b","c","d","e"]
my_array.push "f"
my_array # returns ["a","b","c","d","e","f"]

The push method will always add values to the end of an array. This is such a common part of storing related data in programs, that Ruby arrays have a second way to write the method, <<:

my_array = ["a","b","c","d"]
my_array << "e"
my_array # returns ["a","b","c","d","e"]

Write a solution to the second method in editing_arrays.rb, add_colors, that first adds "green", then "blue" to the rainbow_colors array.

When completed, the rainbow in your terminal should display something close to this: