module JSON

JavaScript Object Notation (JSON)

JSON is a lightweight data-interchange format.

A JSON value is one of the following:

A JSON array or object may contain nested arrays, objects, and scalars to any depth:

{"foo": {"bar": 1, "baz": 2}, "bat": [0, 1, 2]}
[{"foo": 0, "bar": 1}, ["baz", 2]]

Using Module JSON

To make module JSON available in your code, begin with:

require 'json'

All examples here assume that this has been done.

Parsing JSON

You can parse a String containing JSON data using either of two methods:

where

The difference between the two methods is that JSON.parse! omits some checks and may not be safe for some source data; use it only for data from trusted sources. Use the safer method JSON.parse for less trusted sources.

Parsing JSON Arrays

When source is a JSON array, JSON.parse by default returns a Ruby Array:

json = '["foo", 1, 1.0, 2.0e2, true, false, null]'
ruby = JSON.parse(json)
ruby # => ["foo", 1, 1.0, 200.0, true, false, nil]
ruby.class # => Array

The JSON array may contain nested arrays, objects, and scalars to any depth:

json = '[{"foo": 0, "bar": 1}, ["baz", 2]]'
JSON.parse(json) # => [{"foo"=>0, "bar"=>1}, ["baz", 2]]

Parsing JSON Objects

When the source is a JSON object, JSON.parse by default returns a Ruby Hash:

json = '{"a": "foo", "b": 1, "c": 1.0, "d": 2.0e2, "e": true, "f": false, "g": null}'
ruby = JSON.parse(json)
ruby # => {"a"=>"foo", "b"=>1, "c"=>1.0, "d"=>200.0, "e"=>true, "f"=>false, "g"=>nil}
ruby.class # => Hash

The JSON object may contain nested arrays, objects, and scalars to any depth:

json = '{"foo": {"bar": 1, "baz": 2}, "bat": [0, 1, 2]}'
JSON.parse(json) # => {"foo"=>{"bar"=>1, "baz"=>2}, "bat"=>[0, 1, 2]}

Parsing JSON Scalars

When the source is a JSON scalar (not an array or object), JSON.parse returns a Ruby scalar.

String:

ruby = JSON.parse('"foo"')
ruby # => 'foo'
ruby.class # => String

Integer:

ruby = JSON.parse('1')
ruby # => 1
ruby.class # => Integer

Float:

ruby = JSON.parse('1.0')
ruby # => 1.0
ruby.class # => Float
ruby = JSON.parse('2.0e2')
ruby # => 200
ruby.class # => Float

Boolean:

ruby = JSON.parse('true')
ruby # => true
ruby.class # => TrueClass
ruby = JSON.parse('false')
ruby # => false
ruby.class # => FalseClass

Null:

ruby = JSON.parse('null')
ruby # => nil
ruby.class # => NilClass

Parsing Options

Input Options

Option max_nesting (Integer) specifies the maximum nesting depth allowed; defaults to 100; specify false to disable depth checking.

With the default, false:

source = '[0, [1, [2, [3]]]]'
ruby = JSON.parse(source)
ruby # => [0, [1, [2, [3]]]]

Too deep:

# Raises JSON::NestingError (nesting of 2 is too deep):
JSON.parse(source, {max_nesting: 1})

Bad value:

# Raises TypeError (wrong argument type Symbol (expected Fixnum)):
JSON.parse(source, {max_nesting: :foo})

Option allow_nan (boolean) specifies whether to allow NaN, Infinity, and MinusInfinity in source; defaults to false.

With the default, false:

# Raises JSON::ParserError (225: unexpected token at '[NaN]'):
JSON.parse('[NaN]')
# Raises JSON::ParserError (232: unexpected token at '[Infinity]'):
JSON.parse('[Infinity]')
# Raises JSON::ParserError (248: unexpected token at '[-Infinity]'):
JSON.parse('[-Infinity]')

Allow:

source = '[NaN, Infinity, -Infinity]'
ruby = JSON.parse(source, {allow_nan: true})
ruby # => [NaN, Infinity, -Infinity]
Output Options

Option symbolize_names (boolean) specifies whether returned Hash keys should be Symbols; defaults to false (use Strings).

With the default, false:

source = '{"a": "foo", "b": 1.0, "c": true, "d": false, "e": null}'
ruby = JSON.parse(source)
ruby # => {"a"=>"foo", "b"=>1.0, "c"=>true, "d"=>false, "e"=>nil}

Use Symbols:

ruby = JSON.parse(source, {symbolize_names: true})
ruby # => {:a=>"foo", :b=>1.0, :c=>true, :d=>false, :e=>nil}

Option object_class (Class) specifies the Ruby class to be used for each JSON object; defaults to Hash.

With the default, Hash:

source = '{"a": "foo", "b": 1.0, "c": true, "d": false, "e": null}'
ruby = JSON.parse(source)
ruby.class # => Hash

Use class OpenStruct:

ruby = JSON.parse(source, {object_class: OpenStruct})
ruby # => #<OpenStruct a="foo", b=1.0, c=true, d=false, e=nil>

Option array_class (Class) specifies the Ruby class to be used for each JSON array; defaults to Array.

With the default, Array:

source = '["foo", 1.0, true, false, null]'
ruby = JSON.parse(source)
ruby.class # => Array

Use class Set:

ruby = JSON.parse(source, {array_class: Set})
ruby # => #<Set: {"foo", 1.0, true, false, nil}>

Option create_additions (boolean) specifies whether to use JSON additions in parsing. See JSON Additions.

Generating JSON

To generate a Ruby String containing JSON data, use method JSON.generate(source, opts), where

Generating JSON from Arrays

When the source is a Ruby Array, JSON.generate returns a String containing a JSON array:

ruby = [0, 's', :foo]
json = JSON.generate(ruby)
json # => '[0,"s","foo"]'

The Ruby Array array may contain nested arrays, hashes, and scalars to any depth:

ruby = [0, [1, 2], {foo: 3, bar: 4}]
json = JSON.generate(ruby)
json # => '[0,[1,2],{"foo":3,"bar":4}]'

Generating JSON from Hashes

When the source is a Ruby Hash, JSON.generate returns a String containing a JSON object:

ruby = {foo: 0, bar: 's', baz: :bat}
json = JSON.generate(ruby)
json # => '{"foo":0,"bar":"s","baz":"bat"}'

The Ruby Hash array may contain nested arrays, hashes, and scalars to any depth:

ruby = {foo: [0, 1], bar: {baz: 2, bat: 3}, bam: :bad}
json = JSON.generate(ruby)
json # => '{"foo":[0,1],"bar":{"baz":2,"bat":3},"bam":"bad"}'

Generating JSON from Other Objects

When the source is neither an Array nor a Hash, the generated JSON data depends on the class of the source.

When the source is a Ruby Integer or Float, JSON.generate returns a String containing a JSON number:

JSON.generate(42) # => '42'
JSON.generate(0.42) # => '0.42'

When the source is a Ruby String, JSON.generate returns a String containing a JSON string (with double-quotes):

JSON.generate('A string') # => '"A string"'

When the source is true, false or nil, JSON.generate returns a String containing the corresponding JSON token:

JSON.generate(true) # => 'true'
JSON.generate(false) # => 'false'
JSON.generate(nil) # => 'null'

When the source is none of the above, JSON.generate returns a String containing a JSON string representation of the source:

JSON.generate(:foo) # => '"foo"'
JSON.generate(Complex(0, 0)) # => '"0+0i"'
JSON.generate(Dir.new('.')) # => '"#<Dir>"'

Generating Options

Input Options

Option allow_nan (boolean) specifies whether NaN, Infinity, and -Infinity may be generated; defaults to false.

With the default, false:

# Raises JSON::GeneratorError (920: NaN not allowed in JSON):
JSON.generate(JSON::NaN)
# Raises JSON::GeneratorError (917: Infinity not allowed in JSON):
JSON.generate(JSON::Infinity)
# Raises JSON::GeneratorError (917: -Infinity not allowed in JSON):
JSON.generate(JSON::MinusInfinity)

Allow:

ruby = [Float::NaN, Float::Infinity, Float::MinusInfinity]
JSON.generate(ruby, allow_nan: true) # => '[NaN,Infinity,-Infinity]'

Option max_nesting (Integer) specifies the maximum nesting depth in obj; defaults to 100.

With the default, 100:

obj = [[[[[[0]]]]]]
JSON.generate(obj) # => '[[[[[[0]]]]]]'

Too deep:

# Raises JSON::NestingError (nesting of 2 is too deep):
JSON.generate(obj, max_nesting: 2)
Output Options

The default formatting options generate the most compact JSON data, all on one line and with no whitespace.

You can use these formatting options to generate JSON data in a more open format, using whitespace. See also JSON.pretty_generate.

In this example, obj is used first to generate the shortest JSON data (no whitespace), then again with all formatting options specified:

obj = {foo: [:bar, :baz], bat: {bam: 0, bad: 1}}
json = JSON.generate(obj)
puts 'Compact:', json
opts = {
  array_nl: "\n",
  object_nl: "\n",
  indent: '  ',
  space_before: ' ',
  space: ' '
}
puts 'Open:', JSON.generate(obj, opts)

Output:

Compact:
{"foo":["bar","baz"],"bat":{"bam":0,"bad":1}}
Open:
{
  "foo" : [
    "bar",
    "baz"
],
  "bat" : {
    "bam" : 0,
    "bad" : 1
  }
}

JSON Additions

When you “round trip” a non-String object from Ruby to JSON and back, you have a new String, instead of the object you began with:

ruby0 = Range.new(0, 2)
json = JSON.generate(ruby0)
json # => '0..2"'
ruby1 = JSON.parse(json)
ruby1 # => '0..2'
ruby1.class # => String

You can use JSON additions to preserve the original object. The addition is an extension of a ruby class, so that:

This example shows a Range being generated into JSON and parsed back into Ruby, both without and with the addition for Range:

ruby = Range.new(0, 2)
# This passage does not use the addition for Range.
json0 = JSON.generate(ruby)
ruby0 = JSON.parse(json0)
# This passage uses the addition for Range.
require 'json/add/range'
json1 = JSON.generate(ruby)
ruby1 = JSON.parse(json1, create_additions: true)
# Make a nice display.
display = <<EOT
Generated JSON:
  Without addition:  #{json0} (#{json0.class})
  With addition:     #{json1} (#{json1.class})
Parsed JSON:
  Without addition:  #{ruby0.inspect} (#{ruby0.class})
  With addition:     #{ruby1.inspect} (#{ruby1.class})
EOT
puts display

This output shows the different results:

Generated JSON:
  Without addition:  "0..2" (String)
  With addition:     {"json_class":"Range","a":[0,2,false]} (String)
Parsed JSON:
  Without addition:  "0..2" (String)
  With addition:     0..2 (Range)

The JSON module includes additions for certain classes. You can also craft custom additions. See Custom JSON Additions.

Built-in Additions

The JSON module includes additions for certain classes. To use an addition, require its source:

To reduce punctuation clutter, the examples below show the generated JSON via puts, rather than the usual inspect,

BigDecimal:

require 'json/add/bigdecimal'
ruby0 = BigDecimal(0) # 0.0
json = JSON.generate(ruby0) # {"json_class":"BigDecimal","b":"27:0.0"}
ruby1 = JSON.parse(json, create_additions: true) # 0.0
ruby1.class # => BigDecimal

Complex:

require 'json/add/complex'
ruby0 = Complex(1+0i) # 1+0i
json = JSON.generate(ruby0) # {"json_class":"Complex","r":1,"i":0}
ruby1 = JSON.parse(json, create_additions: true) # 1+0i
ruby1.class # Complex

Date:

require 'json/add/date'
ruby0 = Date.today # 2020-05-02
json = JSON.generate(ruby0) # {"json_class":"Date","y":2020,"m":5,"d":2,"sg":2299161.0}
ruby1 = JSON.parse(json, create_additions: true) # 2020-05-02
ruby1.class # Date

DateTime:

require 'json/add/date_time'
ruby0 = DateTime.now # 2020-05-02T10:38:13-05:00
json = JSON.generate(ruby0) # {"json_class":"DateTime","y":2020,"m":5,"d":2,"H":10,"M":38,"S":13,"of":"-5/24","sg":2299161.0}
ruby1 = JSON.parse(json, create_additions: true) # 2020-05-02T10:38:13-05:00
ruby1.class # DateTime

Exception (and its subclasses including RuntimeError):

require 'json/add/exception'
ruby0 = Exception.new('A message') # A message
json = JSON.generate(ruby0) # {"json_class":"Exception","m":"A message","b":null}
ruby1 = JSON.parse(json, create_additions: true) # A message
ruby1.class # Exception
ruby0 = RuntimeError.new('Another message') # Another message
json = JSON.generate(ruby0) # {"json_class":"RuntimeError","m":"Another message","b":null}
ruby1 = JSON.parse(json, create_additions: true) # Another message
ruby1.class # RuntimeError

OpenStruct:

require 'json/add/ostruct'
ruby0 = OpenStruct.new(name: 'Matz', language: 'Ruby') # #<OpenStruct name="Matz", language="Ruby">
json = JSON.generate(ruby0) # {"json_class":"OpenStruct","t":{"name":"Matz","language":"Ruby"}}
ruby1 = JSON.parse(json, create_additions: true) # #<OpenStruct name="Matz", language="Ruby">
ruby1.class # OpenStruct

Range:

require 'json/add/range'
ruby0 = Range.new(0, 2) # 0..2
json = JSON.generate(ruby0) # {"json_class":"Range","a":[0,2,false]}
ruby1 = JSON.parse(json, create_additions: true) # 0..2
ruby1.class # Range

Rational:

require 'json/add/rational'
ruby0 = Rational(1, 3) # 1/3
json = JSON.generate(ruby0) # {"json_class":"Rational","n":1,"d":3}
ruby1 = JSON.parse(json, create_additions: true) # 1/3
ruby1.class # Rational

Regexp:

require 'json/add/regexp'
ruby0 = Regexp.new('foo') # (?-mix:foo)
json = JSON.generate(ruby0) # {"json_class":"Regexp","o":0,"s":"foo"}
ruby1 = JSON.parse(json, create_additions: true) # (?-mix:foo)
ruby1.class # Regexp

Set:

require 'json/add/set'
ruby0 = Set.new([0, 1, 2]) # #<Set: {0, 1, 2}>
json = JSON.generate(ruby0) # {"json_class":"Set","a":[0,1,2]}
ruby1 = JSON.parse(json, create_additions: true) # #<Set: {0, 1, 2}>
ruby1.class # Set

Struct:

require 'json/add/struct'
Customer = Struct.new(:name, :address) # Customer
ruby0 = Customer.new("Dave", "123 Main") # #<struct Customer name="Dave", address="123 Main">
json = JSON.generate(ruby0) # {"json_class":"Customer","v":["Dave","123 Main"]}
ruby1 = JSON.parse(json, create_additions: true) # #<struct Customer name="Dave", address="123 Main">
ruby1.class # Customer

Symbol:

require 'json/add/symbol'
ruby0 = :foo # foo
json = JSON.generate(ruby0) # {"json_class":"Symbol","s":"foo"}
ruby1 = JSON.parse(json, create_additions: true) # foo
ruby1.class # Symbol

Time:

require 'json/add/time'
ruby0 = Time.now # 2020-05-02 11:28:26 -0500
json = JSON.generate(ruby0) # {"json_class":"Time","s":1588436906,"n":840560000}
ruby1 = JSON.parse(json, create_additions: true) # 2020-05-02 11:28:26 -0500
ruby1.class # Time

Custom JSON Additions

In addition to the JSON additions provided, you can craft JSON additions of your own, either for Ruby built-in classes or for user-defined classes.

Here's a user-defined class Foo:

class Foo
  attr_accessor :bar, :baz
  def initialize(bar, baz)
    self.bar = bar
    self.baz = baz
  end
end

Here's the JSON addition for it:

# Extend class Foo with JSON addition.
class Foo
  # Serialize Foo object with its class name and arguments
  def to_json(*args)
    {
      JSON.create_id  => self.class.name,
      'a'             => [ bar, baz ]
    }.to_json(*args)
  end
  # Deserialize JSON string by constructing new Foo object with arguments.
  def self.json_create(object)
    new(*object['a'])
  end
end

Demonstration:

require 'json'
# This Foo object has no custom addition.
foo0 = Foo.new(0, 1)
json0 = JSON.generate(foo0)
obj0 = JSON.parse(json0)
# Lood the custom addition.
require_relative 'foo_addition'
# This foo has the custom addition.
foo1 = Foo.new(0, 1)
json1 = JSON.generate(foo1)
obj1 = JSON.parse(json1, create_additions: true)
#   Make a nice display.
display = <<EOT
Generated JSON:
  Without custom addition:  #{json0} (#{json0.class})
  With custom addition:     #{json1} (#{json1.class})
Parsed JSON:
  Without custom addition:  #{obj0.inspect} (#{obj0.class})
  With custom addition:     #{obj1.inspect} (#{obj1.class})
EOT
puts display

Output:

Generated JSON:
  Without custom addition:  "#<Foo:0x0000000006534e80>" (String)
  With custom addition:     {"json_class":"Foo","a":[0,1]} (String)
Parsed JSON:
  Without custom addition:  "#<Foo:0x0000000006534e80>" (String)
  With custom addition:     #<Foo:0x0000000006473bb8 @bar=0, @baz=1> (Foo)

Constants

Infinity
JSON_LOADED
MinusInfinity
NaN
VERSION

JSON version

Attributes

create_id[RW]

Sets or returns create identifier, which is used to decide if the json_create hook of a class should be called; initial value is json_class:

JSON.create_id # => 'json_class'
dump_default_options[RW]

Sets or returns the default options for the JSON.dump method. Initially:

opts = JSON.dump_default_options
opts # => {:max_nesting=>false, :allow_nan=>true, :escape_slash=>false}
generator[R]

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

JSON.generator # => JSON::Ext::Generator
load_default_options[RW]

Sets or returns default options for the JSON.load method. Initially:

opts = JSON.load_default_options
opts # => {:max_nesting=>false, :allow_nan=>true, :allow_blank=>true, :create_additions=>true}
parser[R]

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

JSON.parser # => JSON::Ext::Parser
state[RW]

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

JSON.state # => JSON::Ext::Generator::State

Public Class Methods

JSON[object] → new_array or new_string click to toggle source

If object is a String, calls JSON.parse with object and opts (see method parse):

json = '[0, 1, null]'
JSON[json]# => [0, 1, nil]

Otherwise, calls JSON.generate with object and opts (see method generate):

ruby = [0, 1, nil]
JSON[ruby] # => '[0,1,null]'
# File ext/json/lib/json/common.rb, line 18
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 String.encode.

# File ext/json/lib/json/common.rb, line 632
def self.iconv(to, from, string)
  string.encode(to, from)
end
restore(source, proc = nil, options = {})
Alias for: load

Public Instance Methods

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

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

The default options can be changed via method JSON.dump_default_options.

  • Argument io, if given, should respond to method write; the JSON String is written to io, and io is returned. If io is not given, the JSON String is returned.

  • Argument limit, if given, is passed to JSON.generate as option max_nesting.


When argument io is not given, returns the JSON String generated from obj:

obj = {foo: [0, 1], bar: {baz: 2, bat: 3}, bam: :bad}
json = JSON.dump(obj)
json # => "{\"foo\":[0,1],\"bar\":{\"baz\":2,\"bat\":3},\"bam\":\"bad\"}"

When argument io is given, writes the JSON String to io and returns io:

path = 't.json'
File.open(path, 'w') do |file|
  JSON.dump(obj, file)
end # => #<File:t.json (closed)>
puts File.read(path)

Output:

{"foo":[0,1],"bar":{"baz":2,"bat":3},"bam":"bad"}
# File ext/json/lib/json/common.rb, line 610
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) → new_string click to toggle source

Arguments obj and opts here are the same as arguments obj and opts in JSON.generate.

By default, generates JSON data without checking for circular references in obj (option max_nesting set to false, disabled).

Raises an exception if obj contains circular references:

a = []; b = []; a.push(b); b.push(a)
# Raises SystemStackError (stack level too deep):
JSON.fast_generate(a)
# File ext/json/lib/json/common.rb, line 314
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) → new_string click to toggle source

Returns a String containing the generated JSON data.

See also JSON.fast_generate, JSON.pretty_generate.

Argument obj is the Ruby object to be converted to JSON.

Argument opts, if given, contains a Hash of options for the generation. See Generating Options.


When obj is an Array, returns a String containing a JSON array:

obj = ["foo", 1.0, true, false, nil]
json = JSON.generate(obj)
json # => '["foo",1.0,true,false,null]'

When obj is a Hash, returns a String containing a JSON object:

obj = {foo: 0, bar: 's', baz: :bat}
json = JSON.generate(obj)
json # => '{"foo":0,"bar":"s","baz":"bat"}'

For examples of generating from other Ruby objects, see Generating JSON from Other Objects.


Raises an exception if any formatting option is not a String.

Raises an exception if obj contains circular references:

a = []; b = []; a.push(b); b.push(a)
# Raises JSON::NestingError (nesting of 100 is too deep):
JSON.generate(a)
# File ext/json/lib/json/common.rb, line 275
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 = {}) → object click to toggle source

Returns the Ruby objects created by parsing the given source.

  • Argument source must be, or be convertible to, a String:

    • If source responds to instance method to_str, source.to_str becomes the source.

    • If source responds to instance method to_io, source.to_io.read becomes the source.

    • If source responds to instance method read, source.read becomes the source.

    • If both of the following are true, source becomes the String 'null':

      • Option allow_blank specifies a truthy value.

      • The source, as defined above, is nil or the empty String ''.

    • Otherwise, source remains the source.

  • Argument proc, if given, must be a Proc that accepts one argument. It will be called recursively with each result (depth-first order). See details below. 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.

  • Argument opts, if given, contains a Hash of options for the parsing. See Parsing Options. The default options can be changed via method JSON.load_default_options=.


When no proc is given, modifies source as above and returns the result of parse(source, opts); see parse.

Source for following examples:

source = <<-EOT
{
"name": "Dave",
  "age" :40,
  "hats": [
    "Cattleman's",
    "Panama",
    "Tophat"
  ]
}
EOT

Load a String:

ruby = JSON.load(source)
ruby # => {"name"=>"Dave", "age"=>40, "hats"=>["Cattleman's", "Panama", "Tophat"]}

Load an IO object:

require 'stringio'
object = JSON.load(StringIO.new(source))
object # => {"name"=>"Dave", "age"=>40, "hats"=>["Cattleman's", "Panama", "Tophat"]}

Load a File object:

path = 't.json'
File.write(path, source)
File.open(path) do |file|
  JSON.load(file)
end # => {"name"=>"Dave", "age"=>40, "hats"=>["Cattleman's", "Panama", "Tophat"]}

When proc is given:

  • Modifies source as above.

  • Gets the result from calling parse(source, opts).

  • Recursively calls proc(result).

  • Returns the final result.

Example:

require 'json'

# Some classes for the example.
class Base
  def initialize(attributes)
    @attributes = attributes
  end
end
class User    < Base; end
class Account < Base; end
class Admin   < Base; end
# The JSON source.
json = <<-EOF
{
  "users": [
      {"type": "User", "username": "jane", "email": "jane@example.com"},
      {"type": "User", "username": "john", "email": "john@example.com"}
  ],
  "accounts": [
      {"account": {"type": "Account", "paid": true, "account_id": "1234"}},
      {"account": {"type": "Account", "paid": false, "account_id": "1235"}}
  ],
  "admins": {"type": "Admin", "password": "0wn3d"}
}
EOF
# Deserializer method.
def deserialize_obj(obj, safe_types = %w(User Account Admin))
  type = obj.is_a?(Hash) && obj["type"]
  safe_types.include?(type) ? Object.const_get(type).new(obj) : obj
end
# Call to JSON.load
ruby = JSON.load(json, proc {|obj|
  case obj
  when Hash
    obj.each {|k, v| obj[k] = deserialize_obj v }
  when Array
    obj.map! {|v| deserialize_obj v }
  end
})
pp ruby

Output:

{"users"=>
   [#<User:0x00000000064c4c98
     @attributes=
       {"type"=>"User", "username"=>"jane", "email"=>"jane@example.com"}>,
     #<User:0x00000000064c4bd0
     @attributes=
       {"type"=>"User", "username"=>"john", "email"=>"john@example.com"}>],
 "accounts"=>
   [{"account"=>
       #<Account:0x00000000064c4928
       @attributes={"type"=>"Account", "paid"=>true, "account_id"=>"1234"}>},
    {"account"=>
       #<Account:0x00000000064c4680
       @attributes={"type"=>"Account", "paid"=>false, "account_id"=>"1235"}>}],
 "admins"=>
   #<Admin:0x00000000064c41f8
   @attributes={"type"=>"Admin", "password"=>"0wn3d"}>}
# File ext/json/lib/json/common.rb, line 536
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
load_file(path, opts={}) → object click to toggle source

Calls:

parse(File.read(path), opts)

See method parse.

# File ext/json/lib/json/common.rb, line 224
def load_file(filespec, opts = {})
  parse(File.read(filespec), opts)
end
load_file!(path, opts = {}) click to toggle source

Calls:

JSON.parse!(File.read(path, opts))

See method parse!

# File ext/json/lib/json/common.rb, line 235
def load_file!(filespec, opts = {})
  parse!(File.read(filespec), opts)
end
parse(source, opts) → object click to toggle source

Returns the Ruby objects created by parsing the given source.

Argument source contains the String to be parsed.

Argument opts, if given, contains a Hash of options for the parsing. See Parsing Options.


When source is a JSON array, returns a Ruby Array:

source = '["foo", 1.0, true, false, null]'
ruby = JSON.parse(source)
ruby # => ["foo", 1.0, true, false, nil]
ruby.class # => Array

When source is a JSON object, returns a Ruby Hash:

source = '{"a": "foo", "b": 1.0, "c": true, "d": false, "e": null}'
ruby = JSON.parse(source)
ruby # => {"a"=>"foo", "b"=>1.0, "c"=>true, "d"=>false, "e"=>nil}
ruby.class # => Hash

For examples of parsing for all JSON data types, see Parsing JSON.

Parses nested JSON objects:

source = <<-EOT
{
"name": "Dave",
  "age" :40,
  "hats": [
    "Cattleman's",
    "Panama",
    "Tophat"
  ]
}
EOT
ruby = JSON.parse(source)
ruby # => {"name"=>"Dave", "age"=>40, "hats"=>["Cattleman's", "Panama", "Tophat"]}

Raises an exception if source is not valid JSON:

# Raises JSON::ParserError (783: unexpected token at ''):
JSON.parse('')
# File ext/json/lib/json/common.rb, line 194
def parse(source, opts = {})
  Parser.new(source, **(opts||{})).parse
end
parse!(source, opts) → object click to toggle source

Calls

parse(source, opts)

with source and possibly modified opts.

Differences from JSON.parse:

  • Option max_nesting, if not provided, defaults to false, which disables checking for nesting depth.

  • Option allow_nan, if not provided, defaults to true.

# File ext/json/lib/json/common.rb, line 209
def parse!(source, opts = {})
  opts = {
    :max_nesting  => false,
    :allow_nan    => true
  }.merge(opts)
  Parser.new(source, **(opts||{})).parse
end
pretty_generate(obj, opts = nil) → new_string click to toggle source

Arguments obj and opts here are the same as arguments obj and opts in JSON.generate.

Default options are:

{
  indent: '  ',   # Two spaces
  space: ' ',     # One space
  array_nl: "\n", # Newline
  object_nl: "\n" # Newline
}

Example:

obj = {foo: [:bar, :baz], bat: {bam: 0, bad: 1}}
json = JSON.pretty_generate(obj)
puts json

Output:

{
  "foo": [
    "bar",
    "baz"
  ],
  "bat": {
    "bam": 0,
    "bad": 1
  }
}
# File ext/json/lib/json/common.rb, line 369
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

Private Instance Methods

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