Ruby objects and JSON serialization (without Rails)

Question

I\'m trying to understand the JSON serialization landscape in Ruby. I\'m new to Ruby.

Is there any good JSON serialization options if you are not working with Rails?

Answer 1

Jbuilder is a gem built by rails community. But it works well in non-rails environments and have a cool set of features.

# suppose we have a sample object as below
sampleObj.name #=> foo
sampleObj.last_name #=> bar

# using jbuilder we can convert it to json:
Jbuilder.encode do |json|
  json.name sampleObj.name
  json.last_name sampleObj.last_name
end #=> "{:\"name\" => \"foo\", :\"last_name\" => \"bar\"}"

Answer 2

require 'json'
{"foo" => "bar"}.to_json
# => "{\"foo\":\"bar\"}"

Answer 3

To get the build in classes (like Array and Hash) to support as_json and to_json, you need to require 'json/add/core' (see the readme for details)

Answer 4

If rendering performance is critical, you might also want to look at yajl-ruby, which is a binding to the C yajl library. The serialization API for that one looks like:

require 'yajl'
Yajl::Encoder.encode({"foo" => "bar"}) #=> "{\"foo\":\"bar\"}"

Answer 5

Check out Oj. There are gotchas when it comes to converting any old object to JSON, but Oj can do it.

require 'oj'

class A
    def initialize a=[1,2,3], b='hello'
        @a = a
        @b = b
    end
end

a = A.new
puts Oj::dump a, :indent => 2

This outputs:

{
  "^o":"A",
  "a":[
    1,
    2,
    3
  ],
 "b":"hello"
}

Note that ^o is used to designate the object's class, and is there to aid deserialization. To omit ^o, use :compat mode:

puts Oj::dump a, :indent => 2, :mode => :compat

Output:

{
  "a":[
    1,
    2,
    3
  ],
  "b":"hello"
}

Answer 6

Since I searched a lot myself to serialize a Ruby Object to json:

require 'json'

class User
  attr_accessor :name, :age

  def initialize(name, age)
    @name = name
    @age = age
  end

  def as_json(options={})
    {
      name: @name,
      age: @age
    }
  end

  def to_json(*options)
    as_json(*options).to_json(*options)
  end
end

user = User.new("Foo Bar", 42)
puts user.to_json #=> {"name":"Foo Bar","age":42}