Advanced Hashes Hashketball

Learning Goals

  • Practice iterating over nested hashes.


Welcome to the second part of Hashketball. In this lab, you will be implementing methods to work with a nested data structure. You've already built the structure in the previous lab, so we've provided it for you in this lab.

To recap - your task is to use Ruby to help you perform analysis on an NBA game. Process the nested data structure to produce insights about how various players performed.

We also strongly recommend that you read the entire README before you start coding. We're going to show some tips and tricks that make the coding a lot easier...but only if you read through to the end.

Code your solution in hashketball.rb following the steps below. The solution from the previous lab is implemented in game_hash. Note that the tests are still present, so the first tests will already be passing. Keep game_hash as is, using the other methods to access information.

Building Methods

We have a nested data structure. Now we need to process it to produce insights. Since you have a thorough understanding of the nested data structure (you wrote it, after all), we don't need to review things like using pp to "pretty-print" the nested data structure. We can pick up on our process from where we need to start processing the nested data structure into insights.

  1. Ensure you can read data out of the nested data structure with simple, basic [] calls.

    You can confirm this by starting IRB from this lesson's main directory and requiring the hashketball.rb file with require './hashketball.rb'

    2.6.1 :001 > require './hashketball.rb'
     => true

    Once required, you can interact with the game_hash method. Calling game_hash[:home][:team_name], for example, should return "Brooklyn Nets". This is because game_hash returns a hash - we can chain [] calls the hash it returns.

  2. Wrap basic code that "reaches into" the nested data structure in methods that have friendly human-names. Wrap basic (or "First Order") methods into methods that do more ("Nth Order") and are human-brain-friendly (list_snacks)

  3. Be flexible; work from what you have to where you want to go; or, work backward; or, make a midpoint between what you have and what you need to have

While you might have seen this pattern with simple nested data structure work, this pattern is still valid. The only thing that's changed is that in some places you can see where an Enumerable could make your code clearer and briefer. This process works. Take this lab as a chance to hone your skills attacking BIG problems with process on your side.

Applying Nested Data Structure-Processing Process

Run learn. There are a whole bunch of methods that are expected to exist. The first one is num_points_scored. But there's so much output. Let's make it more manageable.

We can run this method's test, again by using the -e or --example flag: rspec spec/hashketball_spec.rb -e num_points_scored.

PRO TIP: You can use this strategy to run small chunks of the test suite. Simply look in the spec/hashketball_spec.rb file and find a describe block. You can run all the tests under it by using that block's String as an argument to -e.

That num_points_scored method produces an insight. Here's a specification:

  • Build a method, num_points_scored that takes in an argument of a player's name and returns the number of points scored for that player.

Why don't we define that method and have it return game_hash?

def num_points_scored

Run the test again. Sure enough, our method fails (unsurprisingly), but the test results have changed. Continue to add code to get num_points_scored working. If you need to "invent" helper methods, to help you process game_hash, do so! Here's some sample thought process:

Think about where in the hash you will find a player's :points. How can you iterate down into that level? Think about the return value of your method. Remember that .each returns the original collection that you are iterating over. How can you return the number of points for a particular player? How would we have done it with a simple while loop? Which Enumerable helps here? Is a while-loop better than an Enumerable? Etc.

If you repeat the process we just explored together, you will be able to deliver more complex methods to satisfy tests. Find a failing test, build a "skeleton method," iterate on the code, get success, and move on. This is the way software is "grown" in the real world.

Additional Methods

  • Build a method, shoe_size, that takes in an argument of a player's name and returns the shoe size for that player.

    • Think about how you will find the shoe size of the correct player. How can you check and see if a player's name matches the name that has been passed into the method as an argument?
  • Build a method, team_colors, that takes in an argument of the team name and returns an Array of that team's colors.

  • Build a method, team_names, that operates on the game Hash to return an Array of the team names.

  • Build a method, player_numbers, that takes in an argument of a team name and returns an Array of the jersey numbers for that team.

  • Build a method, player_stats, that takes in an argument of a player's name and returns a hash of that player's stats.

    • Check out the following example of the expected return value of the player_stats method:
  player_stats("Alan Anderson")
  => {
        :player_name => "Alan Anderson",
        :number => 0,
        :shoe => 16,
        :points => 22,
        :rebounds => 12,
        :assists => 12,
        :steals => 3,
        :blocks => 1,
        :slam_dunks => 1
  • Build a method, big_shoe_rebounds, that will return the number of rebounds associated with the player that has the largest shoe size. Break this one down into steps:

    • First, find the player with the largest shoe size
    • Then, return that player's number of rebounds
    • Remember to think about return values here.

Bonus Questions:

If you would like to take on a few more challenges, there are a few more things you can do. There are not tests for this content - these are provide for additional practice working with hash data.

Define methods to return the answer to the following questions:

  1. Which player has the most points? Call the method most_points_scored.

  2. Which team has the most points? Call the method winning_team.

  3. Which player has the longest name? Call the method player_with_longest_name.

Super Bonus:

  1. Write a method that returns true if the player with the longest name had the most steals. Call the method long_name_steals_a_ton?.

"I am completely stuck"

This is a challenging lab. Process, small methods, helper methods. All of these are tools that are designed to get you un-stuck.

One last tool is the "Pry" debugging library - it can be a real help.

From the command line run the command gem install pry if you haven't installed it already. If the gem command returns telling you that pry was installed or that it's already installed, the following should work for you.

Next, at the top of hashketball.rb put the line require "pry".

Using Pry, when running RSpec tests with the learn command, we can pause the execution of our Ruby code. This allows us to step into the code and play with any available variables or methods that are in scope.

We tell Ruby where to pause by writing binding.pry in our code. When Ruby sees that magic word, it will stop execution and hand things over to a REPL called Pry. It's there that we can do the inspection.

Below is an example start for num_points_scored with binding.pry included:

def num_points_scored(player_name)
  game_hash.each do |location, team_data|
    #are you ABSOLUTELY SURE what 'location' and 'team data' are? use binding.pry to find out!
    team_data.each do |attribute, data|
      #are you ABSOLUTELY SURE what 'attribute' and 'team data' are? use binding.pry to find out!

      #what is 'data' at each loop throughout .each block? when will the following line of code work and when will it break?
      data.each do |data_item|

At every place Ruby sees binding.pry, it will stop the program's execution. While the program is stopped, you can print out variables that are in scope. At the first binding.pry in the example above, you can type in player_name and have the value printed out by Pry. At the second binding.pry, you will be able to access player_name, location, and team_data and have those values printed out by pry. When you're done at one binding, type exit and the code will resume running (until it hits another binding.pry). If you're all done with a given pry session exit-program or exit! will close Pry and return you to the command-line.

When running learn, if any binding.pry lines are present in the solution, Pry will still kick in so you may want to remove them once you think you've solved a method.


This is a new frontier for you! You are now using powerful tools of Ruby to transform a nested data structure that you made from non-computer-ready data to produce insights. You've made huge strides in becoming a really solid developer in the procedural programming paradigm. This is a huge moment. Celebrate it!

Believe it or not, the code that put rockets in space and mankind on the Moon were only slight variations on this style of programming. You've learned something really powerful!


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