module JSON - Documentation for Ruby 2.3.0 (original) (raw)

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"}"

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"

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 JSON.dump method:

:max_nesting: false :allow_nan: true :quirks_mode: 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 JSON.load method:

:max_nesting: false :allow_nan: true :quirks_mode: 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.

def [](object, opts = {}) if object.respond_to? :to_str JSON.parse(object.to_str, opts) else JSON.generate(object, opts) end end

const_defined_in?(modul, constant) click to toggle source

def self.const_defined_in?(modul, constant) modul.const_defined?(constant) end

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

Encodes string using Ruby's String.encode

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

restore(source, proc = nil, options = {})

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.

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.

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. state is * a JSON::State object,

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:

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.

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.

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[:quirks_mode] && (source.nil? || source.empty?) source = 'null' end result = parse(source, opts) recurse_proc(result, &proc) if proc result end

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:

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:

def parse!(source, opts = {}) opts = { :max_nesting => false, :allow_nan => true }.update(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.

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

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

Private Instance Methods

restore(source, proc = nil, options = {})