Temperature Converter

program.rb

require 'temperature_converter'

#================= Program ==================#
print %Q{
Welcome to super simple temperature converter
=============================================
1. Celsius to Fahrenheit
2. Fahrenheit to Celsius
Please select our converter method[1]:}

method_number = gets.chop
STDOUT.flush
method_number = method_number.empty? ? "1" : method_number

print "Please input the value to be converted:"
from_value = gets.chop
STDOUT.flush

TemperatureConverter.convert(method_number, from_value.to_f)

temperature_converter.rb

class TemperatureConverter
  METHODS = {
    "1" => {  :name => "Celsius to Fahrenheit", 
              :formula => lambda { |value| value * 9/5.0 + 32 },
              :absolute_zero => -273.15
           },
    "2" => {  :name => "Fahrenheit to Celsius",
              :formula => lambda { |value| (value - 32) * 5/9.0 },
              :absolute_zero => -459.67
                
           }
  }
  
  def self.convert(method_number , from_value)
    method = METHODS[method_number]

    raise StandardError.new("Invalid value") if from_value < method[:absolute_zero]
        
    result = method[:formula].call from_value
    print_output(method, from_value, result)
    
    result
  end
  
  def self.print_output(method, from_value, result_value)
    from, result = method[:name].split("to")
    
    puts "Convet from %s= %.2f => %s= %.2f" % [from, from_value, result, result_value]
  end
end