I understand the video well, but I was wondering what the real world applications of using Hash's were. Thanks!

Hi Darian, Hashes are useful for keeping track of items by name rather than by index – it's much easier to see and be specific about what you're trying to find when you can use the actual term, with keys and values that are easy to retrieve.

Particularly I've found when you start sending and receiving data through requests to servers, using forms, and most browser-related data transferral (although this is most often in JSON, but it's really similar)

It makes it so that you can access attributes of the hash object just like they are methods that return a value eg:

cat = {
  name: "missy",
  favourite_food: "biscuits"
  }

# so then if you go 
cat.name # => it should return "missy" to you

# which to me is a bit clearer than if it was an array and you had to say
cat[0] # => to have it return its name, "missy"

One of the most common uses of hashes you're going to end up seeing are objects you look up in the database (using the rails console).

For example, if you create a Rails web app, you are probably going to have a bunch of users you need to store in the database, right? Information will be stored about the users as hashes. You'll type something like "User.first" and it will give you a hash that looks something like this:

id => 1
name => "Joe Cool"
job_type => "Freelancer"
rate_per_hour => 85.00
onboarded_at => June 1, 2015
star_rating => 5
first_review => "Joe did a great job! We really enjoyed using him."
second_review => nil

etc, etc. The keys (e.g. name, job_type, etc) are the names of your columns in the database. The values (e.g. "Joe Cool", "Freelancer") are the specific values for the specific user, Joe Cool.

The columns (keys) would have been created by using Rails migrations as you developed the app. For example, "rails generate migration AddStarRatingToUsers star_rating:integer" followed by "rake db:migrate" would add the star_rating column as an integer to your User object in the database.

The values would be assigned as people use your app. For example, when Joe Cool signed up to your website, he filled out a form that asked for his name, job type, and hourly rate. When he submitted the form, those values were recorded in the database. Later, someone uses Joe and then when they use a form to review his work, they entered in a review and a star rating. When they submitted that form, those values were then recorded for Joe.

If a piece of information has never been entered yet, the value will be nil (i.e. the value for second_review in the example above).