1. Iterate over array elements.
2. Use various methods to manipulate arrays and strings.
3. Convert data types.

In Ruby, there are a few methods available to us for converting data types. For example, it is possible to convert a string to an array, an array into a string, or a range into an array, among other conversions. You can learn more about conversion here, but for now we'll just take a look at a few.

The .split method will convert a string into an array. The .split method takes an argument of the character in the string on which you want to split it. For example, if we have a string that contains a comma-separated list of items:

"hippo,giraffe,monkey,horse"

We can call .split on it, with an argument of a , ("comma") to get an array of animal names:

"hippo,giraffe,monkey,horse".split(",")
  => ["hippo", "giraffe", "monkey", "horse"]

The .to_a method, when called on a range, can convert a range of numbers to an array:

(1..10).to_a
  => [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]

The .join method, when called on an array, will convert it into a string. This method takes in an optional string argument containing either a character or a set of characters that will be inserted between each array element, as they are assembled into a string.

For example, calling .join with no argument will create a string out of the array's elements by placing each one directly adjacent to the next one:

["a", "b", "c"].join
  => "abc"

But calling .join on the same array and giving it an argument of a " :-) " ("smiley face") will place an occurrence of that string, (i.e. the smiley face) between each letter:

["a", "b", "c"].join(" :-) ")
  => "a :-) b :-) c"

• Fork and clone this lab.
• Write a method oxford_comma that takes an array of string elements as an argument and converts it into a string using the Oxford comma. For example, the array ["fiddleheads","okra","kohlrabi"] should get converted to the string "fiddleheads, okra, and kohlrabi".
  • Hint: You will need to refer to the section above about converting arrays into strings, but note that coding this method will involve a couple of extra challenges.
  • Hint: Remember, strings can be operated on very similarly to arrays. For instance, you can add elements to the end of strings with the << ("shovel") method just like you can with arrays.
• Run learn test and read through the errors to see the specific cases your method will need to handle.
• This might be a challenging lab, so take your time using Google and playing around with your code. Good luck and have fun!

• Wikipedia - Serial Comma
• Dot Net Perls - Convert