# module 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:

    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
    :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 `JSON.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 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

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

Encodes string using Ruby's String.encode

    # File ext/json/lib/json/common.rb, line 406
    def self.iconv(to, from, string)
      string.encode(to, from)
    end

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

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,

- 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.

    # 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

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 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

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 ext/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 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) 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 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

recurse_proc(result, &proc) click to toggle source

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

    # 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

### Private Instance Methods

restore(source, proc = nil, options = {})
Alias for: load