Ruby:同时循环两个散列，其中一个是嵌套散列

Question

我是编码和 ruby​​ 的新手，有一项类作业。我们应该从出租车司机的 excel 中获取数据集，并找出每个司机的乘车次数和收入。我们可以自由地以任何我们想要的方式构建代码。下面是我的代码。

我想做的是计算乘车次数并将它们存储在散列 rides_per_driver 中。但是，通过 if 语句，我得到了“没有将 Array 隐式转换为 Integer (TypeError)”。如何让程序为 rides_per_driver 获取 keys 并迭代哈希 rides？

感谢任何帮助。谢谢

# Stored rides data.
rides = {
  ride_1: {
    driver_id: "DR0004",
    date: "3rd Feb 2016",
    cost: 5,
    rider_id: "RD0022",
    rating: 5
  },

  ride_2: {
    driver_id: "DR0001",
    date: "3rd Feb 2016",
    cost: 10,
    rider_id: "RD0003",
    rating: 3
  },

 ride_3: {
    driver_id: "DR0002",
    date: "3rd Feb 2016",
    cost: 25,
    rider_id: "RD0073",
    rating: 5
  }
}



# iterate over the hash of hashes. If the driver id is x then
# add one ride to the tally.



# Storage for number of rides per driver
rides_per_driver = {
  "DR0001" => 0,
  "DR0002" => 0,
  "DR0003" => 0,
  "DR0004" => 0
}
amount_earned_per_driver = []

rides_per_driver.each do |x|
  if rides_per_driver.has_key?(rides_per_driver[x])
    rides.each do|ride_num, ride_data|
      rides.each do |k, v|
        rides_per_driver += 1
      end
    end
  else
    rides.each do|ride_num, ride_data|
      rides.each do |k, v|
        rides_per_driver = 1
      end
    end
  end


end

Answer 1

rides = [
  { driver_id: "DR0004", date: "3rd Feb 2016", cost:  5, rider_id: "RD0022", rating: 5 },
  { driver_id: "DR0001", date: "3rd Feb 2016", cost: 10, rider_id: "RD0003", rating: 3 },
  { driver_id: "DR0002", date: "3rd Feb 2016", cost: 25, rider_id: "RD0073", rating: 5 },
  { driver_id: "DR0004", date: "3rd Feb 2016", cost:  5, rider_id: "RD0022", rating: 5 },
]

rides.each_with_object({}) do |ride, h|
  h.update(ride[:driver_id]=>{ rides: 1, earnings: ride[:cost] }) do |_,o,n|
    { rides: o[:rides]+1, earnings: o[:earnings]+n[:earnings] }
  end 
end
  #=> {"DR0004"=>{:rides=>2, :earnings=>10},
  #    "DR0001"=>{:rides=>1, :earnings=>10},
  #    "DR0002"=>{:rides=>1, :earnings=>25}}

这使用了 Hash#update 的形式(又名 merge!)，它使用一个 block 来确定要合并的两个散列中存在的键的值。有关详细信息，请参阅文档，尤其是三个 block 变量(_、o 和 n)的定义。 (我用下划线代替了公共(public) key ，以表示该 key 未用于 block 计算。)