bacchusabzal / programming-univbasics-4-building-nested-hashes-dumbo-web-111819

Building Nested Hashes Lab

Learning Goals

• Build a nested hash
• Add key/value pairs in a nested hash
• Update key/value pairs in a nested hash

Introduction

In this lab, we will practice constructing deeply-nested Hash. This means that we'll have a Hash that contains a Hash inside of it. Those "interior" or "inner" Hashes might themselves contain Hashes.

As a reminder, this might look like:

# Greatly abbreviated!
countries_and_capitals_of_the_world = {
  :north_america => {
    "Canada" => {
      :capital => "Ottawa",
      :capital_climate => "Kőppen Dfb"
    },
    "USA" => {
      :capital => "Washington D.C.",
      :capital_climate => "Kőppen Cfa"
    }
  },
  :africa => {
    "Ghana" => {
      :capital => "Accra",
      :capital_climate => "Kőppen Aw"
    },
    "Nigeria" => {
      :capital => "Abuja",
      :capital_climate => "Kőppen Aw"
    }
  }
}

We will work through this lab by filling out the implementation of four methods. Each method will return a Hash that is locally defined within that method's implementation. The comments in ./intro_to_ruby_hashes_lab.rb and the results of running the tests will guide you.

Process

We're going to write the implementation of 4 methods

• base_hash
• monopoly_with_second_tier
• monopoly_with_third_tier
• monopoly_with_fourth_tier

Between the different implementations, we'll build on the previous method's implementation. So the tests will guide you first to a Hash that passes base_hash's test.

Then, you should take the end successful Hash from base_hash and copy it into monopoly_with_second_tier. The monopoly_with_second_tier has some additional expectations so what you just copied won't quite work. The tests will guide you to getting it working. Repeat this process until your methods pass all the tests. If you get stumped, we've included the final Hash in the file final_hash.rb in this repository.

PATTERN FOR LEARNING: We've seen many students take the final answer and pare it down to get the tests passing. This is not a good path to mastering this concept. The path that requires work in programming, at the gym, or in relationships creates the most benefit.

Conclusion

Congratulations! You've built a pretty complex Hash with nesting. This should prove to you that there's very little in this world that can't be modeled with nesting of Hashes, scalar values, and Arrays.

Resources

• Ruby Documentation on Hashes
• What is a Hash in Ruby?