How to Serialize Object to json in Ruby - ruby

Question

I am learning Ruby and am wondering how to serialize a ruby object to json. I am cool using ActiveSupport or any other gems, what is the best way to to this? The following approach doesn't work and fails with
BinaryTree.rb:4:in `require': no such file to load -- json (LoadError)
My question is, what do I install and what require statements would I need to use?
#!/usr/bin/env ruby
require 'pp'
require 'json'
class BinaryTree
attr_accessor :key, :value, :left, :right
def initialize(key=nil,value=nil, left=nil, right=nil)
#key, #value, #left, #right = key, value, left, right
end
def insert(key,value)
if #key.nil?
#key = key
return #value = value
end
if key == #key
return #value = value
end
if key > #key
if #right.nil?
#right = BinaryTree.new
end
return #right.insert(key, value)
end
if #left.nil?
#left = BinaryTree.new
end
return #left.insert(key, value)
end
end
if __FILE__ == $0
bt = BinaryTree.new
bt.insert(5,2)
bt.insert(4,5)
bt.insert(6,3)
bt.insert(9,7)
bt.insert(8,9)
pp bt
puts JSON.encode(bt)
end

Answer 1

Do you have the json gem installed? If not, you'd need to ensure you install that using gem install json first. Once installed, you should be able to do something like the following:
File.open('output_file', 'w') do |f|
f.write(JSON.encode(bt))
end
Using the File.open API with a block is convenient since it will #close the file instance afterward.
Update
If you're on Ruby 1.8 or earlier, you must set up Rubygems first, using the following:
require 'rubygems'
gem 'json'
require 'json'
puts ['test'].to_json