基于键的ruby合并散列数组，并将其按键/值对的数目排序

Question

我有一个哈希数组：

ah = [{"Date"=>"2014-03-17", "countdown 7"=>1}, {"Date"=>"2014-03-17", "voice 6"=>1},     
 {"Date"=>"2014-03-18", "voice 1"=>1}, {"Date"=>"2014-03-18", "voice 2"=>0},     
 {"Date"=>"2014-03-18", "voice 3"=>1}, {"Date"=>"2014-03-18", "voice 4"=>0},    
 {"Date"=>"2014-03-18", "voice 5"=>0}, {"Date"=>"2014-03-18", "voice 6"=>0},     
 {"Date"=>"2014-03-19", "voice 5"=>0}, {"Date"=>"2014-03-19", "voice 6"=>0},    
 {"Date"=>"2014-03-20", "countdown 5"=>1}, {"Date"=>"2014-03-20", "voice 7"=>0},     
 {"Date"=>"2014-03-20", "voice 6"=>0}]   

我想要根据键合并它：

ah = [{"Date"=>"2014-03-17", "countdown 7"=>1, "voice 6"=>1},      
 {"Date"=>"2014-03-18", "voice 1"=>1, "voice 2"=>0, "voice 3"=>1, "voice 4"=>0, "voice 5"=>0, "voice 6"=>0},       
 {"Date"=>"2014-03-19", "voice 5"=>0, "voice 6"=>0},       
 {"Date"=>"2014-03-20", "countdown 5"=>1, "voice 7"=>0, "voice 6"=>0}]         

试过：

ah.inject { |all, h| all.merge(h) } #no success

对怎么做有什么提示吗？

更新

是否可以根据键/值对的数量对其进行排序？因此，具有最大键/值的散列是第一个，而键值最少的散列是最后一个？

输出

[{"Date"=>"2014-03-18", "voice 1"=>1, "voice 2"=>0, "voice 3"=>1, "voice 4"=>0, "voice 5"=>0, "voice 6"=>0},   
 {"Date"=>"2014-03-20", "countdown 5"=>1, "voice 7"=>0, "voice 6"=>0},
 {"Date"=>"2014-03-17", "countdown 7"=>1, "voice 6"=>1},              
 {"Date"=>"2014-03-19", "voice 5"=>0, "voice 6"=>0}       
]       

**最新情况2 **

若要按键/值对的长度排序散列数组，请执行以下操作：

ah.sort {|a, b| a.length <=> b.length}.reverse  

Answer 1

我会这样做：

ah.group_by { |h| h['Date'] }.map { |_,v| v.inject(:update) }
# => [{"Date"=>"2014-03-17", "countdown 7"=>1, "voice 6"=>1},
#     {"Date"=>"2014-03-18",
#      "voice 1"=>1,
#      "voice 2"=>0,
#      "voice 3"=>1,
#      "voice 4"=>0,
#      "voice 5"=>0,
#      "voice 6"=>0},
#     {"Date"=>"2014-03-19", "voice 5"=>0, "voice 6"=>0},
#     {"Date"=>"2014-03-20", "countdown 5"=>1, "voice 7"=>0, "voice 6"=>0}]