What I have is :
{"Key1":[{"key2":"30"},{"key3":"40"}]}
I wish to convert it to :
{"Key1":{"key2":30,"key3":40}}
2 Answers
You can merge multiple hashes:
[{foo: 1}, {bar: 2}, {baz: 3}].inject(:merge)
#=> {:foo=>1, :bar=>2, :baz=>3}
Applied to your hash:
hash = {"Key1"=>[{"key2"=>"30"}, {"key3"=>"40"}]}
hash["Key1"] = hash["Key1"].inject(:merge)
hash #=> {"Key1"=>{"key2"=>"30", "key3"=>"40"}}
Comments
I'd prefer Stefan's answer as it looks cleaner. Posting this to just show an another approach:
hash = {"key1" => [{"key2" => "30"},{"key3" => "40"}]}
then you can:
hash["key1"] = Hash[hash["key1"].flat_map(&:to_a)]
#=> {"key1"=>{"key2"=>"30", "key3"=>"40"}}
However, I did benchmarking and results were a bit weird:
require 'benchmark'
def with_inject
hash = {"Key1"=>[{"key2"=>"30"}, {"key3"=>"40"}]}
hash["Key1"] = hash["Key1"].inject(:merge)
hash
end
def map_and_flatten
hash = {"key1" => [{"key2" => "30"},{"key3" => "40"}]}
hash["key1"] = Hash[hash["key1"].flat_map(&:to_a)]
hash
end
n = 500000
Benchmark.bm(50) do |x|
x.report("with_inject "){ n.times { with_inject } }
x.report("map_and_flatten "){ n.times { map_and_flatten } }
end
Result with Ruby-1.9.2-p290 -
user system total real
with_inject 2.000000 0.000000 2.000000 ( 2.008612)
map_and_flatten 2.290000 0.010000 2.300000 ( 2.293664)
Result with Ruby-2.0.0-p353 -
user system total real
with_inject 2.350000 0.020000 2.370000 ( 2.366092)
map_and_flatten 2.420000 0.000000 2.420000 ( 2.419962)
Result with Ruby-2-1-2-p95 -
user system total real
with_inject 2.180000 0.010000 2.190000 ( 2.198437)
map_and_flatten 2.100000 0.000000 2.100000 ( 2.104745)
And I'm not sure why map_and_flatten was faster than with_inject in Ruby 2.1.2.
1 Comment
Stefan
Your approach doesn't work if a hash contains more than one key-value pair, e.g.:
Hash[[{a:1},{b:2,c:3}].map(&:flatten)]. But you could use Hash[array.flat_map(&:to_a)] to solve that.
key: valueonly works for symbolic keys, you have to usekey => value.