Rails日期范围JSON数据

Question

我希望日期范围为1.month.ago..Date.today，然后每天选择最高温度（因此应获得30个单独的数字），然后总结结果。

我以JSON格式获取数据，结构如下

{"status": "ok", "data": [{"temperature": 22.4, "date": "20160815-0345"}}

我通过循环解析数据。

@data['data'].each do |d|
 maxTotal << [DateTime.parse(d['date']), d['temperature']]
end

但没有说明如何选择每天的最大值然后总结。

@total = maxTotal { |a| a[0].to_date == (1.month.ago.to_date) }.max { |a,b| a[1] <=> b[1] }.sum[1]

Answer 1

更新：已测试并正常工作

json_data = @data['data']
sum_of_max_temperature_in_each_day = json_data.
  group_by{ |h| Date.parse(h[:date]) }.
  reject{ |k, v| !( ((30.days.ago.to_date)..(Date.today)) === k ) }.
  inject(0){ |sum, h| sum + h.second.max_by{ |h| h[:temperature] }[:temperature] }

解释（分解）

# Example; let json_data be
json_data = [
  {"temperature": 22.4, "date": "20160815-0345"},
  {"temperature": 10.4, "date": "20160815-1435"},
  {"temperature": 15.8, "date": "20990101-0430"},
  {"temperature": 4, "date": "20160816-0101"}
]

# sum of max temperature each day within last 30 days
puts json_data.
  group_by{ |h| Date.parse(h[:date]) }.
  reject{ |k, v| !( ((30.days.ago.to_date)..(Date.today)) === k ) }.
  inject(0){ |sum, h| sum + h.second.max_by{ |h| h[:temperature] }[:temperature] }
=> 26.4

# 1) Group by day
puts json_data.
  group_by{|h| Date.parse( h[:date] )}
{
  Mon, 15 Aug 2016=>[
    {:temperature=>22.4, :date=>"20160815-0345"},
    {:temperature=>10.4, :date=>"20160815-1435"}
  ],
  Thu, 01 Jan 2099=>[
    {:temperature=>15.8, :date=>"20990101-0430"}
  ],
  Tue, 16 Aug 2016=>[
    {:temperature=>4, :date=>"20160816-0101"}
  ]
}

# 2) Remove those not within the last 30 days
puts json_data.
  group_by{ |h| Date.parse(h[:date]) }.
  reject{ |k, v| !( ((30.days.ago.to_date)..(Date.today)) === k ) }

{
  Mon, 15 Aug 2016=>[
   {:temperature=>22.4, :date=>"20160815-0345"},
   {:temperature=>10.4, :date=>"20160815-1435"}
  ],
  Tue, 16 Aug 2016=>[
    {:temperature=>4, :date=>"20160816-0101"}
  ]
}

# 3) Showing what's happening inside the inject() block.
puts json_data.
  group_by{ |h| Date.parse(h[:date]) }.
  reject{ |k, v| !( ((30.days.ago.to_date)..(Date.today)) === k ) }.
  inject(0){ |sum, h| 
    puts "h ==> #{h}";
    puts "h.second ==> #{h.second}";
    puts "h.second.max_by ==> #{h.second.max_by{ |h| h[:temperature] }[:temperature]}"
  }

h ==> [
  Mon, 15 Aug 2016,
  [
    {:temperature=>22.4, :date=>"20160815-0345"},
    {:temperature=>10.4, :date=>"20160815-1435"}
  ]
]
h.second ==> [
  {:temperature=>22.4, :date=>"20160815-0345"},
  {:temperature=>10.4, :date=>"20160815-1435"}
]
h.second.max_by ==> 22.4
h ==> [
  Tue, 16 Aug 2016, 
  [
    {:temperature=>4, :date=>"20160816-0101"}
  ]
]
h.second ==> [
  {:temperature=>4, :date=>"20160816-0101"}
]
h.second.max_by ==> 4