method

deep_symbolize_keys

Importance_2
v4.2.9 - Show latest stable - 2 notes - Class: Hash
deep_symbolize_keys() public

Returns a new hash with all keys converted to symbols, as long as they respond to to_sym. This includes the keys from the root hash and from all nested hashes and arrays.

hash = { 'person' => { 'name' => 'Rob', 'age' => '28' } }

hash.deep_symbolize_keys
# => {:person=>{:name=>"Rob", :age=>"28"}}
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April 23, 2014
0 thanks

Does not symbolize hashes in nested arrays

If you have a nested structure containing arrays of hashes, you still need to do that on your own, eg.

module SymbolizeHelper
  def symbolize_recursive(hash)
    {}.tap do |h|
      hash.each { |key, value| h[key.to_sym] = map_value(value) }
    end
  end

  def map_value(thing)
    case thing
    when Hash
      symbolize_recursive(thing)
    when Array
      thing.map { |v| map_value(v) }
    else
      thing
    end
  end
end

Or, if you want to get really fancy with Ruby refinements (YMMV), one could do

module SymbolizeHelper
  extend self

  def symbolize_recursive(hash)
    {}.tap do |h|
      hash.each { |key, value| h[key.to_sym] = transform(value) }
    end
  end

  private

  def transform(thing)
    case thing
    when Hash; symbolize_recursive(thing)
    when Array; thing.map { |v| transform(v) }
    else; thing
    end
  end

  refine Hash do
    def deep_symbolize_keys
      SymbolizeHelper.symbolize_recursive(self)
    end
  end
end

And later say

using SymbolizeHelper # augmented Hash#deep_symbolize_keys is now available
April 2, 2020 - (>= v4.2.1)
0 thanks

Works even on nested structures

@EdvardM added a note years ago saying this does not symbolize the keys of deeply nested hashes, which may have been the case for whatever version of ruby was available at the time, but in 4+, it definitely does work as described:

hash = {"a" => :a, "b" => {z: [[{"c" => 3}, {"c" => 4}], []]}}
hash.deep_symbolize_keys
=> {:a=>:a, :b=>{:z=>[[{:c=>3}, {:c=>4}], []]}}