Ruby 按日期分组和求和哈希数组

我有这样一个哈希数组：

[{:created=>Fri, 22 Jan 2014 13:02:13 UTC +00:00, :amount=>20}, 
{:created=>Fri, 27 Jan 2014 13:14:57 UTC +00:00, :amount=>15}, 
{:created=>Fri, 27 Jan 2014 14:42:40 UTC +00:00, :amount=>10}, 
{:created=>Fri, 28 Jan 2014 15:26:58 UTC +00:00, :amount=>10}, 
{:created=>Fri, 28 Jan 2014 15:30:18 UTC +00:00, :amount=>20}, 
{:created=>Fri, 31 Jan 2014 15:32:46 UTC +00:00, :amount=>50}, 
{:created=>Fri, 31 Jan 2014 15:33:29 UTC +00:00, :amount=>40}]

我想按日期对这些散列进行分组，并求和金额。因此，在我的示例中，输出将是：

[{:created=>"2014-01-22", :amount=>20}, 
{:created=>"2014-01-27", :amount=>25}, 
{:created=>"2014-01-28", :amount=>30}, 
{:created=>"2014-01-31", :amount=>90}]

我会这样做：

require 'date'

a = [{:created=> 'Fri, 22 Jan 2014 13:02:13 UTC +00:00', :amount=>20}, 
{:created=>'Fri, 27 Jan 2014 13:14:57 UTC +00:00', :amount=>15}, 
{:created=>'Fri, 27 Jan 2014 14:42:40 UTC +00:00', :amount=>10}, 
{:created=>'Fri, 28 Jan 2014 15:26:58 UTC +00:00', :amount=>10}, 
{:created=>'Fri, 28 Jan 2014 15:30:18 UTC +00:00', :amount=>20}, 
{:created=>'Fri, 31 Jan 2014 15:32:46 UTC +00:00', :amount=>50}, 
{:created=>'Fri, 31 Jan 2014 15:33:29 UTC +00:00', :amount=>40}]

hsh = a.group_by { |h| Date.parse h[:created] }.map do |k,v| 
  {:created => k.to_s,:amount => v.map {|h1| h1[:amount]}.inject(:+)} 
end
hsh
# => [{:created=>"2014-01-22", :amount=>20},
#     {:created=>"2014-01-27", :amount=>25},
#     {:created=>"2014-01-28", :amount=>30},
#     {:created=>"2014-01-31", :amount=>90}]

---

我认为Arup将字符串解析为日期是明智的，但是

…group_by{h | h[：created]。first（16）}…

也可以工作（或者您可以使用正则表达式）。使用

Date.parse

的一个优点是，如果发现日期字符串不合法，将引发异常。除了OP的日期值不是字符串之外；它们是

Date

对象（否则会被引用）。@Matt没什么大不了的。。。在这种情况下，我将使用

h[：created].to_s

而不是

Date.parse h[：created]

。。我将编写

：created=>k..

，而不是

：created=>k..

。但我写的，就是这个想法。