class Oj::ScHandler

A Simple Callback Parser (SCP) for JSON. The Oj::ScHandler class should be subclassed and then used with the Oj.sc_parse() method. The Scp methods will then be called as the file is parsed. The handler does not have to be a subclass of the ScHandler class as long as it responds to the desired methods.

@example

require 'oj'

class MyHandler < ::Oj::ScHandler
  def hash_start
    {}
  end

  def hash_set(h,k,v)
    h[k] = v
  end

  def array_start
    []
  end

  def array_append(a,v)
    a << v
  end

  def add_value(v)
    p v
  end

  def error(message, line, column)
    p "ERROR: #{message}"
  end
end

File.open('any.json', 'r') do |f|
  Oj.sc_parse(MyHandler.new, f)
end

To make the desired methods active while parsing the desired method should be made public in the subclasses. If the methods remain private they will not be called during parsing.

def hash_start(); end
def hash_end(); end
def hash_key(key); end
def hash_set(h, key, value); end
def array_start(); end
def array_end(); end
def array_append(a, value); end
def add_value(value); end

As certain elements of a JSON document are reached during parsing the callbacks are called. The parser helps by keeping track of objects created by the callbacks but does not create those objects itself.

hash_start

When a JSON object element starts the #hash_start() callback is called if public. It should return what ever Ruby Object is to be used as the element that will later be included in the #hash_set() callback.

hash_end

When a hash key is encountered the #hash_key method is called with the parsed hash value key. The return value from the call is then used as the key in the key-value pair that follows.

hash_key

At the end of a JSON object element the #hash_end() callback is called if public.

hash_set

When a key value pair is encountered during parsing the #hash_set() callback is called if public. The first element will be the object returned from the enclosing #hash_start() callback. The second argument is the key and the last is the value.

array_start

When a JSON array element is started the #array_start() callback is called if public. It should return what ever Ruby Object is to be used as the element that will later be included in the #array_append() callback.

array_end

At the end of a JSON array element the #array_end() callback is called if public.

array_append

When a element is encountered that is an element of an array the #array_append() callback is called if public. The first argument to the callback is the Ruby object returned from the enclosing #array_start() callback.

add_value

The handler is expected to handle multiple JSON elements in one stream, file, or string. When a top level JSON has been read completely the #add_value() callback is called. Even if only one element was ready this callback returns the Ruby object that was constructed during the parsing.

Public Class Methods

new() click to toggle source

Create a new instance of the ScHandler class.

# File lib/oj/schandler.rb, line 108
def initialize()
end

Private Instance Methods

add_value(value) click to toggle source
# File lib/oj/schandler.rb, line 135
def add_value(value)
end
array_append(a, value) click to toggle source
# File lib/oj/schandler.rb, line 138
def array_append(a, value)
end
array_end() click to toggle source
# File lib/oj/schandler.rb, line 132
def array_end()
end
array_start() click to toggle source
# File lib/oj/schandler.rb, line 129
def array_start()
end
hash_end() click to toggle source
# File lib/oj/schandler.rb, line 119
def hash_end()
end
hash_key(key) click to toggle source
# File lib/oj/schandler.rb, line 122
def hash_key(key)
  key
end
hash_set(h, key, value) click to toggle source
# File lib/oj/schandler.rb, line 126
def hash_set(h, key, value)
end
hash_start() click to toggle source

To make the desired methods active while parsing the desired method should be made public in the subclasses. If the methods remain private they will not be called during parsing.

# File lib/oj/schandler.rb, line 116
def hash_start()
end