How do I convert a String object into a Hash object?

Question

I have a string which looks like a hash:

"{ :key_a => { :key_1a => 'value_1a', :key_2a => 'value_2a' }, :key_b => { :key_1b => 'value_1b' } }"

How do I get a Hash out of it? like:

{ :key_a => { :key_1a => 'value_1a', :key_2a => 'value_2a' }, :key_b => { :key_1b => 'value_1b' } }

The string can have any depth of nesting. It has all the properties how a valid Hash is typed in Ruby.

Answer 1

For different string, you can do it without using dangerous eval method:

hash_as_string = "{\"0\"=>{\"answer\"=>\"1\", \"value\"=>\"No\"}, \"1\"=>{\"answer\"=>\"2\", \"value\"=>\"Yes\"}, \"2\"=>{\"answer\"=>\"3\", \"value\"=>\"No\"}, \"3\"=>{\"answer\"=>\"4\", \"value\"=>\"1\"}, \"4\"=>{\"value\"=>\"2\"}, \"5\"=>{\"value\"=>\"3\"}, \"6\"=>{\"value\"=>\"4\"}}"
JSON.parse hash_as_string.gsub('=>', ':')

Answer 2

Quick and dirty method would be

eval("{ :key_a => { :key_1a => 'value_1a', :key_2a => 'value_2a' }, :key_b => { :key_1b => 'value_1b' } }") 

But it has severe security implications.
It executes whatever it is passed, you must be 110% sure (as in, at least no user input anywhere along the way) it would contain only properly formed hashes or unexpected bugs/horrible creatures from outer space might start popping up.

Answer 3

The string created by calling Hash#inspect can be turned back into a hash by calling eval on it. However, this requires the same to be true of all of the objects in the hash.

If I start with the hash {:a => Object.new}, then its string representation is "{:a=>#<Object:0x7f66b65cf4d0>}", and I can't use eval to turn it back into a hash because #<Object:0x7f66b65cf4d0> isn't valid Ruby syntax.

However, if all that's in the hash is strings, symbols, numbers, and arrays, it should work, because those have string representations that are valid Ruby syntax.

Answer 4

I had the same problem. I was storing a hash in Redis. When retrieving that hash, it was a string. I didn't want to call eval(str) because of security concerns. My solution was to save the hash as a json string instead of a ruby hash string. If you have the option, using json is easier.

  redis.set(key, ruby_hash.to_json)
  JSON.parse(redis.get(key))

TL;DR: use to_json and JSON.parse