How to change hash keys from `Symbol`s to `String`s?

simply call stringify_keys (or stringify_keys!)

http://apidock.com/rails/Hash/stringify_keys

Use stringify_keys/stringify_keys! methods of the Hash class.

You can also use some_hash.with_indifferent_access to return a Hash instance where your key can be specified as symbols or as strings with no difference.

stringify_keys is nice, but only available in Rails. Here's how I would do it in a single line, with zero dependencies:

new_hash = Hash[your_hash.collect{|k,v| [k.to_s, v]}]

This works on Ruby 1.8.7 and up. If you are working with Ruby 2.1, you can do:

new_hash = a.collect{|k,v| [k.to_s, v]}.to_h

Note that this solution is not recursive, nor will it handle "duplicate" keys properly. eg. if you have :key and also "key" as keys in your hash, the last one will take precedence and overwrite the first one.

hash = hash.transform_keys(&:to_s) turns all keys from symbols into strings.

More here: https://ruby-doc.org/core-2.6.3/Hash.html#method-i-transform_keys

This was added in ruby 2.5: https://bugs.ruby-lang.org/issues/13583