Module: JSON

Relationships & Source Files
Namespace Children
Modules: `Ext`
Classes: `GenericObject`
Exceptions: `CircularDatastructure`, `GeneratorError`, `JSONError`, `MissingUnicodeSupport`, `NestingError`, `ParserError`
Defined in:	ext/json/lib/json.rb, ext/json/generator/generator.c, ext/json/lib/json/common.rb, ext/json/lib/json/ext.rb, ext/json/lib/json/generic_object.rb, ext/json/lib/json/version.rb, ext/json/parser/parser.c

Overview

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:

1. A collection of name/value pairs. Often referred to as an _object_, hash table, record, struct, keyed list, or associative array.
2. 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\"}"

.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"

Constant Summary

Infinity =
# File 'ext/json/lib/json/common.rb', line 102
```
1.0/0
```
JSON_LOADED =
# File 'ext/json/lib/json/ext.rb', line 14
```
true
```
MinusInfinity =
# File 'ext/json/lib/json/common.rb', line 104
```
-Infinity
```
NaN =
# File 'ext/json/lib/json/common.rb', line 100
```
0.0/0
```
UnparserError =

For backwards compatibility

# File 'ext/json/lib/json/common.rb', line 129
```
GeneratorError
```
VERSION =

JSON version

# File 'ext/json/lib/json/version.rb', line 4
```
'2.3.0'
```
VERSION_ARRAY = Internal use only
# File 'ext/json/lib/json/version.rb', line 5
```
VERSION.split(/\./).map { |x| x.to_i }
```
VERSION_BUILD = Internal use only
# File 'ext/json/lib/json/version.rb', line 8
```
VERSION_ARRAY[2]
```
VERSION_MAJOR = Internal use only
# File 'ext/json/lib/json/version.rb', line 6
```
VERSION_ARRAY[0]
```
VERSION_MINOR = Internal use only
# File 'ext/json/lib/json/version.rb', line 7
```
VERSION_ARRAY[1]
```

Class Attribute Summary

.create_id rw

This is create identifier, which is used to decide if the json_create hook of a class should be called.
.dump_default_options rw

The global default options for the .dump method: :max_nesting: false :allow_nan: true :allow_blank: true.
.generator rw

Returns the JSON generator module that is used by JSON.
.load_default_options rw

The global default options for the .load method: :max_nesting: false :allow_nan: true :allow_blank: true.
.parser rw

Returns the JSON parser class that is used by JSON.
.state rw

Returns the JSON generator state class that is used by JSON.
.generator=(generator) rw Internal use only

::Set the module generator to be used by JSON.
.parser=(parser) rw Internal use only

::Set the JSON parser class parser to be used by JSON.

Class Method Summary

.[](object, opts = {})

If object is string-like, parse the string and return the parsed result as a Ruby data structure.
.iconv(to, from, string)

Encodes string using Ruby’s String.encode.
.dump(obj, anIO = nil, limit = nil) mod_func

Dumps obj as a JSON string, i.e. calls generate on the object and returns the result.
.fast_generate(obj, opts = nil) (also: .fast_unparse) mod_func

Generate a JSON document from the Ruby data structure obj and return it.
.fast_unparse mod_func
.generate(obj, opts = nil) (also: .unparse) mod_func

Generate a JSON document from the Ruby data structure obj and return it.
.load(source, proc = nil, options = {}) (also: .restore) mod_func

Load a ruby data structure from a JSON source and return it.
.parse(source, opts = {}) mod_func

Parse the JSON document source into a Ruby data structure and return it.
.parse!(source, opts = {}) mod_func

Parse the JSON document source into a Ruby data structure and return it.
.pretty_generate(obj, opts = nil) (also: .pretty_unparse) mod_func

Generate a JSON document from the Ruby data structure obj and return it.
.pretty_unparse mod_func
.recurse_proc(result, &proc) mod_func

Recursively calls passed Proc if the parsed data structure is an Array or Hash.
.restore mod_func
.unparse mod_func
.deep_const_get(path) Internal use only

Return the constant located at path.

Class Attribute Details

.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’.

[ GitHub ]

# File 'ext/json/lib/json/common.rb', line 96


attr_accessor :create_id

.dump_default_options (rw)

The global default options for the .dump method:

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

[ GitHub ]

# File 'ext/json/lib/json/common.rb', line 362


attr_accessor :dump_default_options

.generator (rw)

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

[ GitHub ]

# File 'ext/json/lib/json/common.rb', line 88


attr_reader :generator

.generator=(generator) (rw)

This method is for internal use only.

::Set the module generator to be used by JSON.

[ GitHub ]

# File 'ext/json/lib/json/common.rb', line 52


def generator=(generator) # :nodoc:
  old, $VERBOSE = $VERBOSE, nil
  @generator = generator
  generator_methods = generator::GeneratorMethods
  for const in generator_methods.constants
    klass = deep_const_get(const)
    modul = generator_methods.const_get(const)
    klass.class_eval do
      instance_methods(false).each do |m|
        m.to_s == 'to_json' and remove_method m
      end
      include modul
    end
  end
  self.state = generator::State
  const_set :State, self.state
  const_set :SAFE_STATE_PROTOTYPE, State.new
  const_set :FAST_STATE_PROTOTYPE, State.new(
    :indent         => '',
    :space          => '',
    :object_nl      => "",
    :array_nl       => "",
    :max_nesting    => false
  )
  const_set :PRETTY_STATE_PROTOTYPE, State.new(
    :indent         => '  ',
    :space          => ' ',
    :object_nl      => "\n",
    :array_nl       => "\n"
  )
ensure
  $VERBOSE = old
end

.load_default_options (rw)

The global default options for the .load method:

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

[ GitHub ]

# File 'ext/json/lib/json/common.rb', line 300


attr_accessor :load_default_options

.parser (rw)

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

[ GitHub ]

# File 'ext/json/lib/json/common.rb', line 23


attr_reader :parser

.parser=(parser) (rw)

This method is for internal use only.

::Set the JSON parser class parser to be used by JSON.

[ GitHub ]

# File 'ext/json/lib/json/common.rb', line 26


def parser=(parser) # :nodoc:
  @parser = parser
  remove_const :Parser if const_defined?(:Parser, false)
  const_set :Parser, parser
end

.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.

[ GitHub ]

# File 'ext/json/lib/json/common.rb', line 92


attr_accessor :state

Class Method Details

.[](object, opts = {})

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.

[ GitHub ]

# File 'ext/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

.deep_const_get(path)

This method is for internal use only.

Return the constant located at path. The format of path has to be either ::A::B::C or A::B::C. In any case, A has to be located at the top level (absolute namespace path?). If there doesn’t exist a constant at the given path, an ArgumentError is raised.

[ GitHub ]

# File 'ext/json/lib/json/common.rb', line 36


def deep_const_get(path) # :nodoc:
  path.to_s.split(/::/).inject(Object) do |p, c|
    case
    when c.empty?                  then p
    when p.const_defined?(c, true) then p.const_get(c)
    else
      begin
        p.const_missing(c)
      rescue NameError => e
        raise ArgumentError, "can't get const #{path}: #{e}"
      end
    end
  end
end

.dump(obj, anIO = nil, limit = nil) (mod_func)

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.

[ GitHub ]

# File 'ext/json/lib/json/common.rb', line 384


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) (mod_func) Also known as: .fast_unparse

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.

[ GitHub ]

# File 'ext/json/lib/json/common.rb', line 239


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

.fast_unparse (mod_func)

[ GitHub ]

# File 'ext/json/lib/json/common.rb', line 260


alias fast_unparse fast_generate

.generate(obj, opts = nil) (mod_func) Also known as: .unparse

Generate a JSON document from the Ruby data structure obj and return it. state is * a JSON::State object,

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

that is used as or to configure a State object.

It defaults to a state object, that creates the shortest possible JSON text in one line, checks for circular data structures and doesn’t allow NaN, Infinity, and -Infinity.

A state hash can have the following keys:

indent: a string used to indent levels (default: ”),
space: a string that is put after, a : or , 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.

[ GitHub ]

# File 'ext/json/lib/json/common.rb', line 208


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

.iconv(to, from, string)

Encodes string using Ruby’s String.encode

[ GitHub ]

# File 'ext/json/lib/json/common.rb', line 406


def self.iconv(to, from, string)
  string.encode(to, from)
end

.load(source, proc = nil, options = {}) (mod_func) Also known as: .restore

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.

[ GitHub ]

# File 'ext/json/lib/json/common.rb', line 323


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

.parse(source, opts = {}) (mod_func)

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

[ GitHub ]

# File 'ext/json/lib/json/common.rb', line 155


def parse(source, opts = {})
  Parser.new(source, **(opts||{})).parse
end

.parse!(source, opts = {}) (mod_func)

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.

[ GitHub ]

# File 'ext/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) (mod_func) Also known as: .pretty_unparse

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.

[ GitHub ]

# File 'ext/json/lib/json/common.rb', line 270


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

.pretty_unparse (mod_func)

[ GitHub ]

# File 'ext/json/lib/json/common.rb', line 291


alias pretty_unparse pretty_generate

.recurse_proc(result, &proc) (mod_func)

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

[ GitHub ]

# File 'ext/json/lib/json/common.rb', line 341


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

.restore (mod_func)

[ GitHub ]

# File 'ext/json/lib/json/common.rb', line 354


alias restore load

.unparse (mod_func)

[ GitHub ]

# File 'ext/json/lib/json/common.rb', line 230


alias unparse generate