How does this work?

select_vs_find.rb

#!/usr/bin/env ruby

# For reference see https://github.com/cogcmd/pagerduty/blob/master/lib/cog_cmd/pagerduty/oncall.rb#L29

# Some test users
users = [{id: 1,
          name: "Bob",
          email: "bob@example.com",
          policy_ids: [1,2]},
         {id: 2,
          name: "Sue",
          email: "sue@example.com",
          policy_ids: [1]},
         {id: 3,
          name: "Fred",
          email: "fred@example.com",
          policy_ids: [2]},
         {id: 4,
          name: "Heather",
          email: "heather@example.com",
          policy_ids: [3]}]

# Some test services
services = [{id: 100,
             name: "Corp Site",
             escalation_policy: {id: 1}},
            {id: 101,
             name: "Prod DB",
             escalation_policy: {id: 2}},
            {id: 102,
             name: "Network",
             escalation_policy: {id: 3}}]

formatted_services = services.map do |service|
  oncall_via_find = users.find do |user|
    user[:policy_ids].include?(service[:escalation_policy][:id])
  end
  oncall_via_select = users.select do |user|
    user[:policy_ids].include?(service[:escalation_policy][:id])
  end
  {
    name: service[:name],
    id: service[:id],
    oncall_find: oncall_via_find,
    oncall_select: oncall_via_select
  }
end

# Note the difference between oncall_find and oncall_select
formatted_services.each do | s |
  puts "---------------"
  puts "Name: #{s[:name]}"
  puts "Id: #{s[:id]}"
  puts "++++++++++"
  puts "Oncall users (find): #{s[:oncall_find]}"
  puts "++++++++++"
  puts "Oncall users (select): #{s[:oncall_select]}"
end