Convert Collection in Ruby

How can I convert a Collection from One type to another in Ruby.

I have a collection MileageRecords(Date, Odometer, Gallons) and would like to generate a li开发者_JAVA技巧st of FooObject(Miles, MPG). The FooObject properties are calculated from the Mileage record.

This gets me the data, but I don't see how to create a collection

LogEntry.all.each_with_index do |log, index|
  if index > 0
    miles = LogEntry.all[index - 1].odometer - log.odometer
    mpg = miles / log.gallons
    puts "#{log.date} #{miles} #{mpg}"
  end
end

You can't do any sort of implicit type casting, especially with your own classes. The best method is probably to create a to_foo_object method for MileageRecords

class MileageRecords
  def to_foo_object
    FooObject.new(miles, mpg) # you'll need to define these variables somehow
  end
end

Then you can call

mileage_records.map{|mr| mr.to_foo_object }

or to shorten it up a bit

mileage_records.map(&:to_foo_object)

How about:

fuel_economy = LogEntry.all.each_cons(2).map do |prev, curr|
   miles = curr.odometer - prev.odometer
   mpg = miles / curr.gallons
   FuelEconomy.new(miles, mpg)
end