Streaming Json parsing: implest class to build from Oj.saj_parse and JrJackson::Json.sj_parse

some_model.rb

class SomeModel
  def null(*) end
  ATTRS = ['v_string', 'v_num', 'v_boolean', 'v_decimal']
  attr_accessor *ATTRS.map(&:to_sym)
  METHODMAP = Hash.new(instance_method(:null))
  ATTRS.each {|attr| METHODMAP[attr] = instance_method("#{attr}=") }

  def self.load(hash) new.load(hash); end

  def load(hash)
    @v_string, @v_num, @v_boolean, @v_decimal = hash.values_at(*ATTRS)
    self
  end

  def add_value(value, key)
    METHODMAP[key].bind(self).call(value)
  end

  def to_s
    "<SomeModel @v_string: '#{v_string}', @v_num: #{v_num}, @v_boolean: #{v_boolean}, @v_decimal: #{v_decimal}"
  end
end

sm = SomeModel.new #=> #<SomeModel:0x007f898145f878>
sm.add_value('foo','v_string') #=> "foo"
sm.to_s #=> "<SomeModel @v_string: 'foo', @v_num: , @v_boolean: , @v_decimal: "
sm.add_value('v_string','foo:') #=> nil
sm.to_s #=> "<SomeModel @v_string: 'foo', @v_num: , @v_boolean: , @v_decimal: "

json_source = %Q|{
  "v_num": 3,
  "v_decimal": 3.333,
  "v_boolean" : true,
  "v_string": "message"
}|

model = SomeModel.new
Oj.saj_parse(model, json_source)
model.to_s #=>  "<SomeModel @v_string: 'message', @v_num: 3, @v_boolean: true, @v_decimal: 3.333"

One could use Virtus or similar, but as this is part of a benchmark, I wanted a Model implementation that contributed as little overhead as possible.

This can be abstracted into a module that one can include in another class.
e.g.

class OtherModel
  include MinimalAttr.new('v_string', 'v_num', 'v_boolean', 'v_decimal')
end