Ruby JSON Analysis Changes Hash Keys

Question

Suppose I have this hash:

{ :info => [ { :from => "Ryan Bates", :message => "sup bra", :time => "04:35 AM" } ] } 

I can call the information array by executing hash[:info] .

Now when I turn this into JSON (JSON.generate) and then parse it (JSON.parse), I get this hash:

 { "info" => [ { "from" => "Ryan Bates", "message" => "sup bra", "time" => "04:35 AM" } ] } 

Now, if I use hash[:info] , it returns nil , but not if I use hash["info"] .

Why is this? And still, to fix this incompatibility (besides using string keys from the very beginning)?

Answer 1

In short, no. Think of it this way, storing characters in JSON is the same as storing strings in JSON. So you cannot distinguish between the two when it comes to parsing a JSON string. You can, of course, convert string keys back to characters, or actually even build a class for interacting with JSON that does this automatically, but I would recommend just using strings.

But, just for the sake of it, here are the answers to this question in previous times: "/ p>

What is the best way to convert a pair of json-formatted key values ​​into a ruby ​​hash with a character as a key?

ActiveSupport :: JSON decodes a hash, losing characters

Or maybe HashWithIndifferentAccess

Answer 2

The JSON generator converts characters to strings because JSON does not support characters. Because JSON keys are all strings, parsing a JSON document by default creates a Ruby hash file with string keys.

You can tell the parser to use characters instead of strings using the symbolize_names parameter.

Example:

 original_hash = {:info => [{:from => "Ryan Bates", :message => "sup bra", :time => "04:35 AM"}]} serialized = JSON.generate(original_hash) new_hash = JSON.parse(serialized, {:symbolize_names => true}) new_hash[:info] #=> [{:from=>"Ryan Bates", :message=>"sup bra", :time=>"04:35 AM"}] 

Link: http://www.ruby-doc.org/stdlib-1.9.3/libdoc/json/rdoc/JSON.html#method-i-parse

Answer 3

I solved my similar problem with calling the with_indifferent_access method on it

Here I have a json string and we can assign it to the s variable

 s = "{\"foo\":{\"bar\":\"cool\"}}" 

So now I can parse the data with the JSON class and assign it to h

 h = JSON.parse(s).with_indifferent_access 

This will create a hash that can take a string or character as a key

 h[:foo]["bar"] #=> "cool" 

Answer 4

• Use ActiveSupport :: JSON.decode, this will make it easier to change json parsers
• Use ActiveSupport :: JSON.decode (my_json, symbolize_names: true)

This will recursively symbolize all keys in the hash.

(confirmed on ruby ​​2.0)

Answer 5

You can change all the keys in the hash to convert them from string to character:

 symbol_hash = Hash[obj.map{ |k,v| [k.to_sym, v] }] puts symbol_hash[:info] # => {"from"=>"Ryan Bates", "message"=>"sup bra", "time"=>"04:35 AM"} 

Unfortunately, this does not work for a hash nested inside an array. You can, however, write a small recursive method that converts all hash keys:

 def symbolize_keys(obj) #puts obj.class # Useful for debugging return obj.collect { |a| symbolize_keys(a) } if obj.is_a?(Array) return obj unless obj.is_a?(Hash) return Hash[obj.map{ |k,v| [k.to_sym, symbolize_keys(v)] }] end symbol_hash = symbolize_keys(hash) puts symbol_hash[:info] # => {:from=>"Ryan Bates", :message=>"sup bra", :time=>"04:35 AM"} 

Answer 6

You cannot use this parameter like this

ActiveSupport::JSON.decode(str_json, symbolize_names: true)

In Rails 4.1 or later, ActiveSupport::JSON.decode no longer accepts a parameter hash for MultiJSON. MultiJSON has reached its end of life and has been deleted.

You can use symbolize_keys to process it.

 ActiveSupport::JSON.decode(str_json).symbolize_keys