ruby-on-rails - 按数据对 JSON 进行分组？

Question

我有以下 JSON 数据:

{
  "events":
  {
      "event":
      [
          {
              "city":"Birmingham",
              "state":"AL",
              "country":"US",
              "lat":"33.5206608",
              "lng":"-86.80249",
              "status":"Delivered",
              "occured_at":"2012-04-06
14:17:00 UTC"
          },
          {
              "city":"Birmingham",
              "state":"AL",
              "country":"US",
              "lat":"33.5206608",
              "lng":"-86.80249",
              "status":"Out
For Delivery",
              "occured_at":"2012-04-06 04:44:00 UTC"
          },
          {
              "city":"Birmingham",
              "state":"AL",
              "country":"US",
              "lat":"33.5206608",
              "lng":"-86.80249",
              "status":"Arrival
Scan",
              "occured_at":"2012-04-05 19:07:00 UTC"
          },
          {
              "city":"Doraville",
              "state":"GA",
              "country":"US",
              "lat":"33.8981579",
              "lng":"-84.2832564",
              "status":"Departure
Scan",
              "occured_at":"2012-04-05 17:08:00 UTC"
          },
          {
              "city":"Doraville",
              "state":"GA",
              "country":"US",
              "lat":"33.8981579",
              "lng":"-84.2832564",
              "status":"Arrival
Scan",
              "occured_at":"2012-04-05 11:15:00 UTC"
          },
          {
              "city":"Spartanburg",
              "state":"SC",
              "country":"US",
              "lat":"34.9495672",
              "lng":"-81.9320482",
              "status":"Departure
Scan",
              "occured_at":"2012-04-05 08:42:00 UTC"
          },
          {
              "city":"Spartanburg",
              "state":"SC",
              "country":"US",
              "lat":"34.9495672",
              "lng":"-81.9320482",
              "status":"Arrival
Scan",
              "occured_at":"2012-04-05 08:21:00 UTC"
          },
          {
              "city":"Greensboro",
              "state":"NC",
              "country":"US",
              "lat":"36.0726354",
              "lng":"-79.7919754",
              "status":"Departure
Scan",
              "occured_at":"2012-04-05 04:45:00 UTC"
          },
          {
              "city":"Greensboro",
              "state":"NC",
              "country":"US",
              "lat":"36.0726354",
              "lng":"-79.7919754",
              "status":"Origin
Scan",
              "occured_at":"2012-04-05 00:11:00 UTC"
          },
          {
              "city":null,
              "state":null,
              "country":"US",
              "status":"Billing
Information Received",
              "occured_at":"2012-04-04 18:20:27 UTC"
          }
      ]
  }
}

我需要做的是按城市、州和国家/地区的组合对数据进行分组，但仍然返回每个项目的数据。

因此，例如，按“伯明翰，阿拉巴马州，美国”分组，但仍然能够遍历每个事件的状态(即已交付、外出交付、到达扫描)那个。

Answer 1

你想要的魔法是Enumerable#group_by :

require 'json'
all = JSON.parse(DATA.read)['events']['event']
all.group_by{ |h| [h['city'],h['state'],h['country']] }.each do |loc,events|
  puts "'#{loc.join(',')}': #{events.length} event#{:s if events.length!=1}"
  print "--> "
  puts events.map{ |e| e['status'] }.join(', ')
end

#=> 'Birmingham,AL,US': 3 events
#=> --> Delivered, Out For Delivery, Arrival Scan
#=> 'Doraville,GA,US': 2 events
#=> --> Departure Scan, Arrival Scan
#=> 'Spartanburg,SC,US': 2 events
#=> --> Departure Scan, Arrival Scan
#=> 'Greensboro,NC,US': 2 events
#=> --> Departure Scan, Origin Scan
#=> ',,US': 1 event
#=> --> Billing Information Received

注意，上面的loc是group_by评估的block返回的三元素数组，events是一个同一组中所有项目的数组。