Hash of Hashes and Captain Planet
Don Cheadle is the best version of Captain Planet there is. I hope you’ve already seen the video. If not, go now. I’ll wait.
As it typically happens, I was creating some nested data structure and was reminded of all the different combinations that there are. For example:
- An array of arrays.
[ [1,2,3], [4,5,6] ] - A hash of arrays.
{ :lucky => [77,42], :unlucky => [666,13] } - An array of hashes.
[ {:cat=>"meow"}, {:dog=>"ruff"} ] - A hash of hashes.
{ :best_in_life => {:enemies => "crushed"}, :worst => { :meatloaf => "old"} }
And I realized that I hadn’t really played with a hash of hashes much. And now I realize why. It’s really pretty useless. It’s hard to work with and the additional key really isn’t all that useful. I found it much better to just denormalize the key into the data attributes. Anyway, you can see what I mean by reading and running what’s below.
We’re going to create Captain Planet and the planeteers in a 2D hash of hashes and do some searching, iterating and other simple things. This should illustrate also how an array of hashes is a bit better. You’ll see halfway through the program we redefine the planeteers.
# search a 2d hash def spacer(msg) puts "\n" puts "-" * 50 puts msg puts "-" * 50 end # this is not really a good data structure but we'll use it anyway. planeteers = { :kwame => { :element => "earth", :from => "Ghana, Africa", :actor => "LeVar Burton" }, :wheeler => { :element => "fire", :from => "Brooklyn, NY", :actor => "Joey Dedio" }, :linka => { :element => "wind", :from => "Soviet Union", :actor => "Kath Soucie" }, :gi => { :element => "water", :from => "Thailand", :actor => "Janice Kawaye" }, :ma_ti => { :element => "heart", :from => "Brazil", :actor => "Scott Menville" } } spacer "Here are our planeteers and their elements:" puts planeteers.keys.collect {|p| {p => planeteers[p][:element]} } puts "\nFind the fire planeteer:\n" fire = planeteers.keys.collect {|p| {p => planeteers[p][:element]=="fire"} } # => [{:kwame=>false}, {:wheeler=>true}, {:linka=>false}, {:gi=>false}, {:ma_ti=>false}] only_fire = fire.select{|h| h.values[0] == true} # => {:wheeler=>true} # print just one puts only_fire.first.keys.first spacer "Let's do this a bit cleaner with a better data structure." planeteers = [ { :name => "kwame", :element => "earth", :from => "Ghana, Africa", :actor => "LeVar Burton" }, { :name => "wheeler", :element => "fire", :from => "Brooklyn, NY", :actor => "Joey Dedio" }, { :name => "linka", :element => "wind", :from => "Soviet Union", :actor => "Kath Soucie" }, { :name => "gi", :element => "water", :from => "Thailand", :actor => "Janice Kawaye" }, { :name => "ma_ti", :element => "heart", :from => "Brazil", :actor => "Scott Menville" } ] planeteers.max_by {|p| p[:name]} # => {:name=>"ma_ti", :element=>"heart", :from=>"Brazil", :actor=>"Scott Menville"} planeteers.max_by {|p| p[:element]} # => {:name=>"linka", :element=>"wind", :from=>"Soviet Union", :actor=>"Kath Soucie"} puts "Find the heart planeteer:" puts planeteers.select {|p| p[:element] == "heart" }.first[:name] # first we'll put a fake planeteer on the end for cpt planet planeteers << { :name => "all", :element => "go planet" } spacer "Let's summon Captain Planet!" planeteers.each do |planeteer| puts "#{planeteer[:name].capitalize}: #{planeteer[:element].capitalize}!" end # pop off fake guy planeteers.pop
Here’s what it spits out:
--------------------------------------------------
Here are our planeteers and their elements:
--------------------------------------------------
{:kwame=>"earth"}
{:wheeler=>"fire"}
{:linka=>"wind"}
{:gi=>"water"}
{:ma_ti=>"heart"}
Find the fire planeteer:
wheeler
--------------------------------------------------
Let's do this a bit cleaner with a better data structure.
--------------------------------------------------
Find the heart planeteer:
ma_ti
--------------------------------------------------
Let's summon Captain Planet!
--------------------------------------------------
Kwame: Earth!
Wheeler: Fire!
Linka: Wind!
Gi: Water!
Ma_ti: Heart!
All: Go planet!