Convert hash keys to lowercase — Ruby Beginner

Question

My table field names are lowercase and the field names I get from CSV files are camelcase. Is there anyway I can convert the keys of an array of hashes to lowercase?

Answer 1

I found that this solution is significantly faster and a bit more "Rubyish".

CSV.foreach(file, :headers => true) do |row|
  new_hash = Hash[row.to_hash.map { |k, v| [k.downcase, v] }]
  Users.create!(new_hash)
end

Answer 2

You could consider using underscore instead of downcase because this would also transform the CamelCase to camel_case notation, which is more Rubylike.

My personal preferences goes to using deep_transform_keys: hash.deep_transform_keys{|key| key.underscore.to_sym }

As transform_keys do not traverse the whole hash.

Answer 3

Since this was tagged with Rails.

With ActiveSupport starting vom version 3.0 you can use a HashWithIndifferentAccess.

That will allow lower/uppercase/symbol writing to access the keys or your Hash.

my_hash = { "camelCase": "some value" }
my_hash.with_indifferent_access[:camelcase] # 'some value'
my_hash.with_indifferent_access['camelcase'] # 'some value'
my_hash.with_indifferent_access['camelCase'] # 'some value'
my_hash.with_indifferent_access['CAMELCASE'] # 'some value'

ActiveSupport 4.0.2 also introduced this:

my_hash.deep_transform_keys!(&:downcase)
# or if your hash isn't nested:
my_hash.transform_keys!(&:downcase)