Method: JSON.load

Defined in:

lib/json/common.rb

.load(source, proc = nil, options = nil) ⇒ Object Also known as: restore

:call-seq:

JSON.load(source, proc = nil, options = {}) -> object

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 'lib/json/common.rb', line 549

def load(source, proc = nil, options = nil)
  opts = if options.nil?
    load_default_options
  else
    load_default_options.merge(options)
  end

  unless source.is_a?(String)
    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
  end

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