在 Ruby 中转换集合

发布于 2024-10-07 16:12:09 字数 410 浏览 1 评论 0原文

如何在 Ruby 中将集合从一种类型转换为另一种类型。

我有一个 MileageRecords(Date, Odometer, Gallons) 集合，并希望生成 FooObject(Miles, MPG) 列表。 FooObject 属性是根据 Mileage 记录计算的。

这为我提供了数据，但我不知道如何创建集合

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

原文

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 list 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

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凉栀 2024-10-14 16:12:09

您不能进行任何类型的隐式类型转换，尤其是对于您自己的类。最好的方法可能是为 MileageRecords 创建一个 to_foo_object 方法

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

然后您可以调用

mileage_records.map{|mr| mr.to_foo_object }

或稍微缩短它

mileage_records.map(&:to_foo_object)

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)

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凌乱心跳 2024-10-14 16:12:09

怎么样：

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

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

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