How to merge array of hashes to get hash of arrays of values
Take your pick:
hs.reduce({}) {|h,pairs| pairs.each {|k,v| (h[k] ||= []) << v}; h}hs.map(&:to_a).flatten(1).reduce({}) {|h,(k,v)| (h[k] ||= []) << v; h}I'm strongly against messing with the defaults for hashes, as the other suggestions do, because then checking for a value modifies the hash, which seems very wrong to me.
How's this?
def collect_values(hashes) h = Hash.new{|h,k| h[k]=[]} hashes.each_with_object(h) do |h, result| h.each{ |k, v| result[k] << v } endendEdit - Also possible with inject, but IMHO not as nice:
def collect_values( hashes ) h = Hash.new{|h,k| h[k]=[]} hashes.inject(h) do |result, h| h.each{ |k, v| result[k] << v } result endend