Unable to use dot syntax for ruby hash

Question

I'm using net/http to pull in some json data from the Yahoo Placemaker API. After receiving the response I am performing JSON.parse on the response. This gives me a hash that looks like:

{"processingTime"=>"0.001493", "version"=>"1.4.0.526 build 111113", "documentLength"=>"25", "document"=>{"administrativeScope"=>{"woeId"=>"2503863", "type"=>"Town", "name"=>"Tampa, FL, US", "centroid"=>{"latitude"=>"27.9465", "longitude"=>"-82.4593"}}, "geographicScope"=>{"woeId"=>"2503863", "type"=>"Town", "name"=>"Tampa, FL, US", "centroid"=>{"latitude"=>"27.9465", "longitude"=>"-82.4593"}}, "localScopes"=>{"localScope"=>{"woeId"=>"2503863", "type"=>"Town", "name"=>"Tampa, FL, US (Town)", "centroid"=>{"latitude"=>"27.9465", "longitude"=>"-82.4593"}, "southWest"=>{"latitude"=>"27.8132", "longitude"=>"-82.6489"}, "northEast"=>{"latitude"=>"28.1714", "longitude"=>"-82.2539"}, "ancestors"=>[{"ancestor"=>{"woeId"=>"12587831", "type"=>"County", "name"=>"Hillsborough"}}, {"ancestor"=>{"woeId"=>"2347568", "type"=>"State", "name"=>"Florida"}}, {"ancestor"=>{"woeId"=>"23424977", "type"=>"Country", "name"=>"United States"}}]}}, "extents"=>{"center"=>{"latitude"=>"27.9465", "longitude"=>"-82.4593"}, "southWest"=>{"latitude"=>"27.8132", "longitude"=>"-82.6489"}, "northEast"=>{"latitude"=>"28.1714", "longitude"=>"-82.2539"}}, "placeDetails"=>{"placeId"=>"1", "place"=>{"woeId"=>"2503863", "type"=>"Town", "name"=>"Tampa, FL, US", "centroid"=>{"latitude"=>"27.9465", "longitude"=>"-82.4593"}}, "placeReferenceIds"=>"1", "matchType"=>"0", "weight"=>"1", "confidence"=>"8"}, "referenceList"=>{"reference"=>{"woeIds"=>"2503863", "placeReferenceId"=>"1", "placeIds"=>"1", "start"=>"15", "end"=>"20", "isPlaintextMarker"=>"1", "text"=>"Tampa", "type"=>"plaintext", "xpath"=>""}}}}

I am able to access elements by doing things like jsonResponse['version'] but I am not able to do jsonResponse.version. Why is this?

Answer 1

If you don't want to install any gems, you can try to use the Ruby's native Struct class and some Ruby tricks, like the splat operator.

# regular hashes
customer = { name: "Maria", age: 21, country: "Brazil" }
customer.name
# => NoMethodError: undefined method `name' for {:name=>"Maria", :age=>21, :country=>"Brazil"}:Hash

# converting a hash to a struct
customer_on_steroids = Struct.new(*customer.keys).new(*customer.values)
customer_on_steroids.name
#=> "Maria"

Please note that this simple solution works only for single-level hashes. To make it dynamic and fully functional for any kind of Hash, you'll have to make it recursive to create substructs inside your struct.

You can also store the Struct as if it was a class.

customer_1 = { name: "Maria", age: 21, country: "Brazil" }
customer_2 = { name: "João",  age: 32, country: "Brazil" }
customer_3 = { name: "José",  age: 43, country: "Brazil" }

Customer = Struct.new(*customer_1.keys)
customer_on_steroids_1 = Customer.new(*customer_1.values)
customer_on_steroids_2 = Customer.new(*customer_2.values) 
customer_on_steroids_3 = Customer.new(*customer_3.values)

Read more about Ruby Struct class.

Answer 2

Hash does not have dot-syntax for it's keys. OpenStruct does:

require 'ostruct'
hash = {:name => 'John'}
os = OpenStruct.new(hash)
p os.name #=> "John"

NOTE: Does not work with nested hashes.