Convert Ruby Hash keys into symbols

Hash Keys to Symbols.rb

hash = { 'foo' => 'bar' }

# Version 1
hash = Hash[hash.map { |k, v| [k.to_sym, v] }]

# Version 2
hash = hash.reduce({}) do |memo, (k, v)| 
  memo.tap { |m| m[k.to_sym] = v }
end

# Version 3
hash = hash.reduce({}) do |memo, (k, v)| 
  memo.merge({ k.to_sym => v})
end

# None of the above solutions work with a multi-level hash
# They only work on the first level: {:foo=>"bar", :level1=>{"level2"=>"baz"}}
# The following two variations solve the problem in the same way

multi_hash = { 'foo' => 'bar', 'level1' => { 'level2' => 'baz' } }

# Modify `Object`
class Object
  def deep_symbolize_keys
    return self.reduce({}) do |memo, (k, v)|
      memo.tap { |m| m[k.to_sym] = v.deep_symbolize_keys }
    end if self.is_a? Hash
    
    return self.reduce([]) do |memo, v| 
      memo << v.deep_symbolize_keys; memo
    end if self.is_a? Array
    
    self
  end
end

multi_hash = multi_hash.deep_symbolize_keys

# Standalone method
def symbolize(obj)
  return obj.reduce({}) do |memo, (k, v)|
    memo.tap { |m| m[k.to_sym] = symbolize(v) }
  end if obj.is_a? Hash
    
  return obj.reduce([]) do |memo, v| 
    memo << symbolize(v); memo
  end if obj.is_a? Array
  
  obj
end

multi_hash = symbolize(multi_hash)

+1

If I'm not wrong, symbolize function must return obj.to_sym

Thanks. I hadn't known about .tap until seeing this example. Handy. I put together a slightly different version of the standalone method to clarify (for myself) the algorithm.

    def symbolize(obj)
      if obj.is_a? Hash
        return obj.inject({}) do |memo, (k, v)|
          memo.tap { |m| m[k.to_sym] = symbolize(v) }
        end
      elsif obj.is_a? Array
        return obj.map { |memo| symbolize(memo) }
      end
      obj
    end

Thank you 👍

Sweet, thanks!

A little trick, using just the Ruby libraries:

hash = { 'foo' => 'bar' }

require 'json'
JSON.parse(hash.to_json, { symbolize_names: true })

With multi hash

multi_hash = { 'foo' => 'bar', 'level1' => { 'level2' => 'baz' } }
=> {"foo"=>"bar", "level1"=>{"level2"=>"baz"}}

JSON.parse(multi_hash.to_json, { symbolize_names: true })
=> {:foo=>"bar", :level1=>{:level2=>"baz"}}

Still easier if you use Rails: https://apidock.com/rails/Hash/symbolize_keys

Very nice approach @martinezcoder

Cool Gist!
@Integralist I would like to add deep_symbolize_keys method to nice_hash gem: https://github.com/MarioRuiz/nice_hash
Since it is yours.... feel free to add it to the Hash class on https://github.com/MarioRuiz/nice_hash/blob/master/lib/nice/hash/add_to_ruby.rb
Or if you prefer it I can do it and name you in the code.

awesome!! @martinezcoder