JSON#load

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.

• Argument opts, if given, contains a Hash of options for the parsing. See Parsing 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 = <<~JSON
  {
    "name": "Dave",
    "age" :40,
    "hats": [
      "Cattleman's",
      "Panama",
      "Tophat"
    ]
  }
JSON

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": "[email protected]"},
      {"type": "User", "username": "john", "email": "[email protected]"}
  ],
  "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
  obj
})
pp ruby

Output:

{"users"=>
   [#<User:0x00000000064c4c98
     @attributes=
       {"type"=>"User", "username"=>"jane", "email"=>"[email protected]"}>,
     #<User:0x00000000064c4bd0
     @attributes=
       {"type"=>"User", "username"=>"john", "email"=>"[email protected]"}>],
 "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"}>}