Reputation: 1836
I want to group an hash by values.
Example:
start_with_hash = { "10:00" => "2014-10-10", "11:00" => "2014-10-10", "11:30" => "2014-10-10, 2014-10-11", "12:00" => "2014-10-11"}
end_with_hash = {"10:00, 11:00" => "2014-10-10", "11:30" => "2014-10-10, 2014-10-11", "12:00" => "2014-10-11" }
Upvotes: 0
Views: 487
Reputation: 5969
not exactly what you asked for:
class Hash
# make a new hash with the existing values as the new keys
# - like #rassoc for each existing key
# - like invert but with *all* keys as array
#
# {1=>2, 3=>4, 5=>6, 6=>2, 7=>4}.flip #=> {2=>[1, 6], 4=>[3, 7], 6=>[5]}
#
def flip
inject({}) { |h, (k,v)| h[v] ||= []; h[v] << k; h }
end
end
start_with_hash.flip
#=> {"2014-10-10"=>["10:00", "11:00"],
"2014-10-10, 2014-10-11"=>["11:30"],
"2014-10-11"=>["12:00"]}
Upvotes: 0
Reputation: 17949
merged_hash = start_with_hash.merge(end_with_hash){|key, oldval, newval| oldval }
more information here http://ruby-doc.org/core-2.1.0/Hash.html#method-i-merge
=> {
"10:00" => "2014-10-10",
"11:00" => "2014-10-10",
"11:30" => "2014-10-10, 2014-10-11",
"12:00" => "2014-10-11",
"10:00, 11:00" => "2014-10-10"
}
Upvotes: 0
Reputation: 118299
I would do as below :
start_with_hash = { "10:00" => "2014-10-10", "11:00" => "2014-10-10", "11:30" => "2014-10-10, 2014-10-11", "12:00" => "2014-10-11"}
Hash[start_with_hash.group_by(&:last).map{|k,v| [v.map(&:first).join(","),k] }]
Upvotes: 3