JSON

JavaScript Object Notation (JSON)¶ ↑

JSON is a lightweight data-interchange format. It is easy for us humans to read and write. Plus, equally simple for machines to generate or parse. JSON is completely language agnostic, making it the ideal interchange format.

Built on two universally available structures:

A collection of name/value pairs. Often referred to as an object, hash table, record, struct, keyed list, or associative array.
An ordered list of values. More commonly called an array, vector, sequence or list.

To read more about JSON visit: json.org

Parsing JSON¶ ↑

To parse a JSON string received by another application or generated within your existing application:

require 'json'

my_hash = JSON.parse('{"hello": "goodbye"}')
puts my_hash["hello"] # => "goodbye"

Notice the extra quotes '' around the hash notation. Ruby expects the argument to be a string and can’t convert objects like a hash or array.

Ruby converts your string into a hash

Generating JSON¶ ↑

Creating a JSON string for communication or serialization is just as simple.

require 'json'

my_hash = {:hello => "goodbye"}
puts JSON.generate(my_hash) # => "{\"hello\":\"goodbye\"}"

Or an alternative way:

require 'json'
puts({:hello => "goodbye"}.to_json) # => "{\"hello\":\"goodbye\"}"

JSON.generate only allows objects or arrays to be converted to JSON syntax. to_json, however, accepts many Ruby classes even though it acts only as a method for serialization:

require 'json'

1.to_json # => "1"

The #generate method accepts a variety of options to set the formatting of string output and defining what input is accepteable. There are also shortcut methods #pretty_generate (with a set of options to generate human-readable multiline JSON) and #fast_generate (with a set of options to generate JSON faster at the price of disabling some checks).

Extended rendering and loading of Ruby objects¶ ↑

JSON library provides optional additions allowing to serialize and deserialize Ruby classes without loosing their type.

# without additions
require "json"
json = JSON.generate({range: 1..3, regex: /test/})
# => '{"range":"1..3","regex":"(?-mix:test)"}'
JSON.parse(json)
# => {"range"=>"1..3", "regex"=>"(?-mix:test)"}

# with additions
require "json/add/range"
require "json/add/regexp"
json = JSON.generate({range: 1..3, regex: /test/})
# => '{"range":{"json_class":"Range","a":[1,3,false]},"regex":{"json_class":"Regexp","o":0,"s":"test"}}'
JSON.parse(json)
# => {"range"=>{"json_class"=>"Range", "a"=>[1, 3, false]}, "regex"=>{"json_class"=>"Regexp", "o"=>0, "s"=>"test"}}
JSON.load(json)
# => {"range"=>1..3, "regex"=>/test/}

See #load for details.

frozen_string_literal: false

Constants

Infinity
JSON_LOADED
MinusInfinity
NaN
UnparserError: This exception is raised if a generator or unparser error occurs.
VERSION: JSON version

Attributes

create_id[RW]

This is create identifier, which is used to decide if the json_create hook of a class should be called. It defaults to ‘json_class’.

dump_default_options[RW]

The global default options for the #dump method:

:max_nesting: false
:allow_nan: true
:allow_blank: true

generator[R]

Returns the JSON generator module that is used by JSON. This is either JSON::Ext::Generator or JSON::Pure::Generator.

load_default_options[RW]

The global default options for the #load method:

:max_nesting: false
:allow_nan: true
:allow_blank: true

parser[R]

Returns the JSON parser class that is used by JSON. This is either JSON::Ext::Parser or JSON::Pure::Parser.

state[RW]

Returns the JSON generator state class that is used by JSON. This is either JSON::Ext::Generator::State or JSON::Pure::Generator::State.

Public Class Methods

[](object, opts = {}) click to toggle source

If object is string-like, parse the string and return the parsed result as a Ruby data structure. Otherwise generate a JSON text from the Ruby data structure object and return it.

The opts argument is passed through to generate/parse respectively. See generate and parse for their documentation.

 
               # File json/lib/json/common.rb, line 13
def [](object, opts = {})
  if object.respond_to? :to_str
    JSON.parse(object.to_str, opts)
  else
    JSON.generate(object, opts)
  end
end

iconv(to, from, string) click to toggle source

Encodes string using Ruby’s String.encode

 
               # File json/lib/json/common.rb, line 409
def self.iconv(to, from, string)
  string.encode(to, from)
end

restore(source, proc = nil, options = {}) click to toggle source

Alias for: load

Public Instance Methods

dump(obj, anIO = nil, limit = nil) click to toggle source

Dumps obj as a JSON string, i.e. calls generate on the object and returns the result.

If anIO (an IO-like object or an object that responds to the write method) was given, the resulting JSON is written to it.

If the number of nested arrays or objects exceeds limit, an ArgumentError exception is raised. This argument is similar (but not exactly the same!) to the limit argument in Marshal.dump.

The default options for the generator can be changed via the ::dump_default_options method.

This method is part of the implementation of the load/dump interface of Marshal and YAML.

 
               # File json/lib/json/common.rb, line 387
def dump(obj, anIO = nil, limit = nil)
  if anIO and limit.nil?
    anIO = anIO.to_io if anIO.respond_to?(:to_io)
    unless anIO.respond_to?(:write)
      limit = anIO
      anIO = nil
    end
  end
  opts = JSON.dump_default_options
  opts = opts.merge(:max_nesting => limit) if limit
  result = generate(obj, opts)
  if anIO
    anIO.write result
    anIO
  else
    result
  end
rescue JSON::NestingError
  raise ArgumentError, "exceed depth limit"
end

fast_generate(obj, opts = nil) click to toggle source

Generate a JSON document from the Ruby data structure obj and return it. This method disables the checks for circles in Ruby objects.

WARNING: Be careful not to pass any Ruby data structures with circles as obj argument because this will cause JSON to go into an infinite loop.

 
               # File json/lib/json/common.rb, line 242
def fast_generate(obj, opts = nil)
  if State === opts
    state, opts = opts, nil
  else
    state = FAST_STATE_PROTOTYPE.dup
  end
  if opts
    if opts.respond_to? :to_hash
      opts = opts.to_hash
    elsif opts.respond_to? :to_h
      opts = opts.to_h
    else
      raise TypeError, "can't convert #{opts.class} into Hash"
    end
    state.configure(opts)
  end
  state.generate(obj)
end

generate(obj, opts = nil) click to toggle source

Generate a JSON document from the Ruby data structure obj and return it. opts is

a Hash like object (responding to to_hash),
or an object convertible into a hash by a to_h method,
or a JSON::State object.

If hash-alike or hash-convertible object is provided, it is internally converted into a State object.

The default options are set to create the shortest possible JSON text in one line, check for circular data structures and do not allow NaN, Infinity, and -Infinity.

An opts hash can have the following keys:

indent: a string used to indent levels (default: ''),
space: a string that is put after a : pair delimiter (default: ''),
space_before: a string that is put before a : pair delimiter (default: ''),
object_nl: a string that is put at the end of a JSON object (default: ''),
array_nl: a string that is put at the end of a JSON array (default: ''),
allow_nan: true if NaN, Infinity, and -Infinity should be generated, otherwise an exception is thrown if these values are encountered. This options defaults to false.
max_nesting: The maximum depth of nesting allowed in the data structures from which JSON is to be generated. Disable depth checking with max_nesting: false, it defaults to 100.

See also the #fast_generate for the fastest creation method with the least amount of sanity checks, and the #pretty_generate method for some defaults for pretty output.

 
               # File json/lib/json/common.rb, line 211
def generate(obj, opts = nil)
  if State === opts
    state, opts = opts, nil
  else
    state = SAFE_STATE_PROTOTYPE.dup
  end
  if opts
    if opts.respond_to? :to_hash
      opts = opts.to_hash
    elsif opts.respond_to? :to_h
      opts = opts.to_h
    else
      raise TypeError, "can't convert #{opts.class} into Hash"
    end
    state = state.configure(opts)
  end
  state.generate(obj)
end

load(source, proc = nil, options = {}) click to toggle source

Load a ruby data structure from a JSON source and return it. A source can either be a string-like object, an IO-like object, or an object responding to the read method. If proc was given, it will be called with any nested Ruby object as an argument recursively in depth first order. To modify the default options pass in the optional options argument as well.

BEWARE: This method is meant to serialise data from trusted user input, like from your own database server or clients under your control, it could be dangerous to allow untrusted users to pass JSON sources into it. The default options for the parser can be changed via the ::load_default_options method.

This method is part of the implementation of the load/dump interface of Marshal and YAML.

 
               # File json/lib/json/common.rb, line 326
def load(source, proc = nil, options = {})
  opts = load_default_options.merge options
  if source.respond_to? :to_str
    source = source.to_str
  elsif source.respond_to? :to_io
    source = source.to_io.read
  elsif source.respond_to?(:read)
    source = source.read
  end
  if opts[:allow_blank] && (source.nil? || source.empty?)
    source = 'null'
  end
  result = parse(source, opts)
  recurse_proc(result, &proc) if proc
  result
end

Also aliased as: restore

parse(source, opts = {}) click to toggle source

Parse the JSON document source into a Ruby data structure and return it.

opts can have the following keys:

max_nesting: The maximum depth of nesting allowed in the parsed data structures. Disable depth checking with :max_nesting => false. It defaults to 100.
allow_nan: If set to true, allow NaN, Infinity and -Infinity in defiance of RFC 7159 to be parsed by the Parser. This option defaults to false.
symbolize_names: If set to true, returns symbols for the names (keys) in a JSON object. Otherwise strings are returned. Strings are the default.
create_additions: If set to false, the Parser doesn't create additions even if a matching class and ::create_id was found. This option defaults to false.
object_class: Defaults to Hash
array_class: Defaults to Array

 
               # File json/lib/json/common.rb, line 155
def parse(source, opts = {})
  Parser.new(source, **(opts||{})).parse
end

parse!(source, opts = {}) click to toggle source

Parse the JSON document source into a Ruby data structure and return it. The bang version of the parse method defaults to the more dangerous values for the opts hash, so be sure only to parse trusted source documents.

opts can have the following keys:

max_nesting: The maximum depth of nesting allowed in the parsed data structures. Enable depth checking with :max_nesting => anInteger. The parse! methods defaults to not doing max depth checking: This can be dangerous if someone wants to fill up your stack.
allow_nan: If set to true, allow NaN, Infinity, and -Infinity in defiance of RFC 7159 to be parsed by the Parser. This option defaults to true.
create_additions: If set to false, the Parser doesn't create additions even if a matching class and ::create_id was found. This option defaults to false.

 
               # File json/lib/json/common.rb, line 174
def parse!(source, opts = {})
  opts = {
    :max_nesting  => false,
    :allow_nan    => true
  }.merge(opts)
  Parser.new(source, **(opts||{})).parse
end

pretty_generate(obj, opts = nil) click to toggle source

Generate a JSON document from the Ruby data structure obj and return it. The returned document is a prettier form of the document returned by unparse.

The opts argument can be used to configure the generator. See the generate method for a more detailed explanation.

 
               # File json/lib/json/common.rb, line 273
def pretty_generate(obj, opts = nil)
  if State === opts
    state, opts = opts, nil
  else
    state = PRETTY_STATE_PROTOTYPE.dup
  end
  if opts
    if opts.respond_to? :to_hash
      opts = opts.to_hash
    elsif opts.respond_to? :to_h
      opts = opts.to_h
    else
      raise TypeError, "can't convert #{opts.class} into Hash"
    end
    state.configure(opts)
  end
  state.generate(obj)
end

recurse_proc(result, &proc) click to toggle source

Recursively calls passed Proc if the parsed data structure is an Array or Hash

 
               # File json/lib/json/common.rb, line 344
def recurse_proc(result, &proc)
  case result
  when Array
    result.each { |x| recurse_proc x, &proc }
    proc.call result
  when Hash
    result.each { |x, y| recurse_proc x, &proc; recurse_proc y, &proc }
    proc.call result
  else
    proc.call result
  end
end

Home Classes Methods

In Files

Namespace

Methods

Class/Module Index