按日期优化哈希的分组数组

Question

Given array

[
  {date: '2014-01-01', a: 5, b:1},
  {date: '2014-01-01', xyz: 11},
  {date: '2014-10-10', qbz: 5},
  {date: '2014-10-10', v: 4, q: 1, strpm: -99}
]

I want to group by date and output an array of hashes

ouput = [
 {date: 2014-01-01, a: 5, b:1, xyz: 11 },
 {date: 2014-10-10, qbz: 5, v: 4, q: 1, strpm: -99},
]

I am solving it in Ruby and have a solution but it seems inefficient.

def arrayt(inputarray)
    outputarray=[];
    inputarray.each do |x|
        tindex = includes(outputarray,x[:date])
        if tindex == -1
            outputarray.push(x)
        else
            outputarray[tindex].merge!(x)
        end
    end
    return outputarray
end

def includes(array,date)
    array.each_with_index do |temp,index|
        if date==temp[:date]
            return index
        end
    end
    return -1
end

Any help with a more elegant solution would be appreciated

Answer 1

[
  {date: '2014-01-01', a: 5, b:1},
  {date: '2014-01-01', xyz: 11},
  {date: '2014-10-10', qbz: 5},
  {date: '2014-10-10', v: 4, q: 1, strpm: -99}
]
.group_by(&:first).map{|_, v| v.inject(:merge)}

Answer 2

Here's a way that employs the form of Hash#update (aka merge! ) that uses a block to determine the values of keys that are present in both hashes being merged:

arr.each_with_object({}) { |g,h|
  h.update({ g[:date]=>g }) { |_,ov,nv| ov.merge(nv) } }.values

To wit:

    hash = arr.each_with_object({}) { |g,h|
      h.update({ g[:date]=>g }) { |_,ov,nv| ov.merge(nv) } }
    #=>{"2014-01-01"=>{:date=>"2014-01-01", :a=>5, :b=>1, :xyz=>11},
    #   "2014-10-10"=>{:date=>"2014-10-10", :qbz=>5, :v=>4, :q=>1, :strpm=>-99}} 
    hash.values
    #=> [{:date=>"2014-01-01", :a=>5, :b=>1, :xyz=>11},
    #    {:date=>"2014-10-10", :qbz=>5, :v=>4, :q=>1, :strpm=>-99}]