Consider the following code:
hash1 = {"one" => 1, "two" => 2, "three" => 3}
hash2 = hash1.reduce({}){ |h, (k,v)| h.merge(k => hash1) }
hash3 = hash2.reduce({}){ |h, (k,v)| h.merge(k => hash2) }
hash4 = hash3.reduce({}){ |h, (k,v)| h.merge(k => hash3) }
hash4 is a 'nested' hash i.e. a hash with string keys and similarly 'nested' hash values.
The 'symbolize_keys' method for Hash in Rails lets us easily convert the string keys to symbols. But I'm looking for an elegant way to convert all keys (primary keys plus keys of all hashes within hash4) to symbols.
The point is to save myself from my (imo) ugly solution:
class Hash
def symbolize_keys_and_hash_values
symbolize_keys.reduce({}) do |h, (k,v)|
new_val = v.is_a?(Hash) ? v.symbolize_keys_and_hash_values : v
h.merge({k => new_val})
end
end
end
hash4.symbolize_keys_and_hash_values #=> desired result
FYI: Setup is Rails 3.2.17 and Ruby 2.1.1
Update:
Answer is hash4.deep_symbolize_keys
for Rails <= 5.0
Answer is JSON.parse(JSON[hash4], symbolize_names: true)
for Rails > 5
There are a few ways to do this
There's a deep_symbolize_keys
method in Rails
hash.deep_symbolize_keys!
As mentioned by @chrisgeeq, there is a deep_transform_keys
method that's available from Rails 4.
hash.deep_transform_keys(&:to_sym)
There is also a bang !
version to replace the existing object.
There is another method called with_indifferent_access
. This allows you to access a hash with either a string or a symbol like how params
are in the controller. This method doesn't have a bang counterpart.
hash = hash.with_indifferent_access
The last one is using JSON.parse
. I personally don't like this because you're doing 2 transformations - hash to json then json to hash.
JSON.parse(JSON[h], symbolize_names: true)
UPDATE:
16/01/19 - add more options and note deprecation of deep_symbolize_keys
19/04/12 - remove deprecated note. only the implementation used in the method is deprecated, not the method itself.