Class: TidyJson::Serializer Private

Inherits:
Object show all
Defined in:
lib/tidy_json/serializer.rb

Overview

This class is part of a private API. You should avoid using this class if possible, as it may be removed or be changed in the future.

A purpose-built JSON generator.

Class Method Summary collapse

Class Method Details

.serialize(obj, json_hash) ⇒ {String => #to_s}

This method is part of a private API. You should avoid using this method if possible, as it may be removed or be changed in the future.

Note:

Hashes will be searched for nested objects to a maximum depth of 2; arrays to a maximum depth of 3.

Searches obj for readable attributes, storing them as key-value pairs in json_hash.

Examples:

class Obj
  class Child
    def initialize; @a = { a: 1 } end
     attr_reader :a
  end
  def initialize; @a = { b: Child.new } end
  attr_accessor :a
end

o = Obj.new
puts o.to_tidy_json
<<JSON
{
   "class": "Obj",
   "a": {
      "b": {
        "class": "Obj::Child",
         "a": {
           "a": 1
       }
     }
   }
}
JSON

# depth > 2: unreachable objects are not serialized
o.a = { b: { c: { d: Obj::Child.new } } }
puts o.to_tidy_json
<<JSON
{
   "class": "Obj",
   "a": {
      "b": {
        "c": {
          "d": "#<Obj::Child:0x0000559d4da865c0>"
       }
     }
   }
}
JSON

# object arrays can be nested up to 3 levels deep
o.a = [ [ Obj::Child.new, [ Obj::Child.new, [ Obj::Child.new ] ] ] ]
puts o.to_tidy_json
<<JSON
{
  "class": "Obj",
  "a": [
    {
      "class": "Obj::Child",
      "a": {
        "a": 1
      }
    },
    [
      [
        {
          "class": "Obj::Child",
          "a": {
            "a": 1
          }
        },
        [
          {
            "class": "Obj::Child",
            "a": {
              "a": 1
            }
          }
        ]
      ]
    ]
  ]
}
JSON

Parameters:

  • obj (Object) —

    A Ruby object that can be parsed as JSON.

  • json_hash ({String,Symbol => #to_s}) —

    Accumulator.

Returns:

  • ({String => #to_s}) —

    A hash mapping of obj‘s visible attributes.



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# File 'lib/tidy_json/serializer.rb', line 94

def self.serialize(obj, json_hash)
  obj.instance_variables.each do |m|
    key = m.to_s[/[^@]\w*/].to_sym

    next unless key && !key.eql?('')

    begin
      val = obj.send(key) # assuming readable attributes . . .
    rescue NoMethodError # . . . which may not be always be the case !
      json_hash[key] = nil
    end

    begin
      # process class members of Hash type
      if val.instance_of?(Hash)
        json_hash[key] = val

        val.each.any? do |k, v|
          json_hash[key][k.to_sym] = serialize(v, class: v.class.name) unless v.instance_variables.empty?
        end

      # process class members of Array type
      elsif val.instance_of?(Array)
        json_hash[key] = []

        val.each do |elem|
          i = val.index(elem)

          # member is a multi-dimensional collection
          if elem.respond_to?(:each)
            nested = []
            elem.each do |e|
              j = if elem.respond_to?(:key)
                    elem.key(e)
                  else elem.index(e)
                  end

              # nested element is a class object
              if !e.instance_variables.empty?
                json_hash[key][j] = { class: e.class.name }

                # recur over the contained object
                serialize(e, json_hash[key][j])

              # some kind of collection?
              elsif e.respond_to?(:each)
                temp = []
                e.each do |el|
                  if el.respond_to?(:each)
                    el.each_with_index do |ell, idx|
                      el[idx] = serialize(ell, class: ell.class.name) unless ell.instance_variables.empty?
                    end
                  end
                  temp << if el.instance_variables.empty? then el
                          else JSON.parse(el.stringify)
                          end
                end

                nested << temp

              # scalar type
              else nested << e
              end
            end
            # ~iteration of nested array elements

            json_hash[key] << nested

          # member is a flat array
          elsif !elem.instance_variables.empty? # class object?
            json_hash[key] << { class: elem.class.name }
            serialize(elem, json_hash[key][i])

          # scalar type
          else json_hash[key] << elem
          end
        end
        # ~iteration of top-level array elements

      end
    rescue NoMethodError
      # we expected an array to behave like a hash, or vice-versa
      json_hash.store(key, val) # a shallow copy is better than nothing
    end
  end
  # ~iteration of instance variables

  json_hash
end