Notes/examples for better code

classes.rb

class MailerContact
  def initialize(first_name, last_name)
    @first_name, @last_name = first_name, last_name
  end

  def full_name
    "#{@first_name} #{@last_name}"
  end
end

class Duration
  def initialize(starting_at, ending_at, unit)
    @starting_at, @ending_at, @unit = starting_at, ending_at, unit
  end

  def calculate
    return 0 unless @ending_at and @starting_at
    if @unit == 'hour'
      ((@ending_at - @starting_at) /  1.hour).round(2)
    else # second
      @ending_at - @starting_at
    end
  end
end

class Price
  def initialize(rate, duration)
    @rate, @duration = rate, duration
  end

  def calculate
    @rate * @duration
  end
end

structs.rb

class MailerContact < Struct.new(:first_name, :last_name)
  def full_name
    "#{first_name} #{last_name}"
  end
end

class Duration < Struct.new(:starting_at, :ending_at, :unit)
  def calculate
    return 0 unless ending_at and starting_at
    if unit == 'hour'
      ((ending_at - starting_at) /  1.hour).round(2)
    else # second
      (ending_at - starting_at).round(0)
    end
  end
end

class Price < Struct.new(:rate, :duration)
  def calculate
    rate * duration
  end
end