lololol.rb

# I want to write a method that returns the first number in a sub array where the letter matches a passed in letter
# If passed in letter does not exist, it should return nil
a = [["a", 1], ["b", 2]]
 
>> #Desired Results
>> get_number_for_letter(a, "a")
1
>> get_number_for_letter(a, "b")
2
>> get_number_for_letter(a, "c")
nil

# Implementation
def get_number_for_letter(arr, letter)
  arr.detect([]) { |d| d.first == letter }[1]
end
 
# Error received for case where letter does not exist
# This might just be me not understanding how detect is supposed to work
>> get_number_for_letter(a, "c")
NoMethodError: undefined method `call' for []:Array
  from (irb):17:in `detect'
  from (irb):17
	from /Users/treadwn/.rvm/gems/ruby-1.9.3-p125@goodreads-rails3-ruby19/gems/railties-3.2.12/lib/rails/commands/console.rb:47:in `start'
	from /Users/treadwn/.rvm/gems/ruby-1.9.3-p125@goodreads-rails3-ruby19/gems/railties-3.2.12/lib/rails/commands/console.rb:8:in `start'
	from /Users/treadwn/.rvm/gems/ruby-1.9.3-p125@goodreads-rails3-ruby19/gems/railties-3.2.12/lib/rails/commands.rb:41:in `<top (required)>'
	from script/rails:6:in `require'
	from script/rails:6:in `<main>'