Find all airports in a given set of regions

airport.rb

# app/models/airport.rb

...

# Take a collection of strings representing the starts of ICAO codes, and
# return an a hash of airports in the region, with airport ids as keys and
# IATA codes as values.
# Params:
# +icao_starts+:: An array of strings of the start of ICAO codes (i.e. EG, K)
def self.in_region_hash(icao_starts)
  # Build a querystring of LIKE statements with question marks connected by ORs:
  conditions = icao_starts.map{"icao_code LIKE ?"}.join(" OR ")
  # Create an array of patterns to insert as parameters:
  patterns = icao_starts.map{|start| "#{start}%"}
  # Run the SQL query, expanding the patterns to insert at the question marks:
  matching_airports = Airport.where(conditions, *patterns)
  
  # Create a hash of airport IDs and IATA codes:
  iata_hash = Hash.new
  matching_airports.each{|airport| iata_hash[airport[:id]] = airport[:iata_code]}
  return iata_hash
end

...