interesting.rb

#!/usr/bin/env ruby
require 'debug_inspector'

def find_matchers(keys)
  matchers = []
  matcher_suffixes = ["IS"]
  keys.any? do |key|
    matcher_suffixes.any? do |suffix|
      var = "%s_%s" % [key.upcase, suffix]
      matchers << [var, ENV[var]] if ENV.key?(var)
    end
  end
  matchers
end

def should_i_yield? hash
  matchers = find_matchers(hash.keys)
  matchers.empty? || matchers.all? {|m| matches?(m, hash) }
end

def matches?(matcher, hash)
  name, value = *matcher
  if name.end_with?("_IS")
    key = name[0...-3].downcase.to_sym
    hash[key] == ENV[name]
  end
end

def iterate_interestingly ray, &block
  ray.each do |hash|
    next unless should_i_yield?(hash)
    yield *hash.values
  end
end


# run this with "ruby ./interesting.rb" for full output
# run this with "NAME_IS=Dave ruby ./interesting.rb" to just see Dave
# run this with "AGE_GE=18 ruby ./interesting.rb" to see adults
# run this with "NAME_IS=Dave AGE_GE=18 ruby ./interesting.rb" to see adults named Dave

iterate_interestingly([
                        { name: "Alice", age: 19 },
                        { name: "Bob", age: 16 },
                        { name: "Carol", age: 17 },
                        { name: "Dave", age: 45 },
                        { name: "Dave", age: 15 },
                      ]) do |name, age|
  puts "User #{name} is #{age} years old."
end