• Access data from a nested hash
• Add data to and change data within a nested hash

Now that we've seen some examples of nested hashes, the next step is to get more comfortable with using them. In this lab, we're going to practice accessing and updating data within a nested hash and review what we've covered so far.

In this lab, you'll be filling out the content of a series of methods that we've defined for you. All of the methods expect you to operate on the programmer_hash object, which is already defined and included in the body of each method.

Use the comments in nested.rb and test suite to guide you. Each test is designed to tell you how to pass it.

Keep in mind that you are expected to get these tests to pass by adding or changing information in the hash programmatically. In other words, if you're asked to, for example, change the value of a specific hash key, don't just re-write the hash with the new value! Use the methods we've learned and practiced in previous lessons.

To quickly review, here is an example of adding data to a hash programmatically:

# good example

my_hash = {first: "I'm first!", second: "I'm second!"}
my_hash[:third] = "I'm third!"

puts my_hash
# > {first: "I'm first!", second: "I'm second!", third: "I'm third!"}

Changing a hash by simply re-defining it is not the goal of this lab:

# bad example

my_hash = {first: "I'm first!", second: "I'm second!"}
my_hash = {first: "I'm first!", second: "I'm second!", third: "I'm third!"}

Hint: In some of these methods, you will need to alter programmer_hash, then make sure to return the entire hash, not just the altered value.

This method should return the value of the :grace_hopper key inside programmer_hash.

This method should return what Alan Kay is known for.

This method should return the language that Dennis Ritchie is known for.

Note: The :languages keys inside programmer_hash each store an array. In this case, the test is looking for the value stored in that array.

This method should return a modified programmer_hash to honor Matz, the creator of Ruby. Update the hash so that:

• there is a :yukihiro_matsumoto key alongside :grace_hopper, :alan_kay, and :dennis_ritchie set to a hash
• this nested hash contains :known_for and :languages keys like the others

Matz is known for "Ruby", but his languages should be "LISP" and "C". Return the entire updated hash.

This method should update what Alan Kay is known for to "GUI" and return the updated programmer_hash.

This method should add "Assembly" to Dennis Ritchie's languages array and return the updated programmer_hash.

Adding and updating data in a nested hash is just like adding and updating an ordinary hash. If we know the structure, it is just a matter of using the right combination of keys.

As we see examples of more complex data structures, we'll start to encounter situations where we aren't 100% of the structure of a hash. This is one reason why getting familiar with programmatically changing hash data is critical - we won't always be able to see the hash we're changing. Instead, we'll have to write logic that and correctly handles accessing and updating hash data in a more abstracted way.