Class: Hash

Overview

:nodoc:

Direct Known Subclasses

HashWithIndifferentAccess

Constant Summary

Constants included from ActiveSupport::CoreExtensions::Hash::Conversions

ActiveSupport::CoreExtensions::Hash::Conversions::XML_FORMATTING, ActiveSupport::CoreExtensions::Hash::Conversions::XML_PARSING, ActiveSupport::CoreExtensions::Hash::Conversions::XML_TYPE_NAMES

Instance Method Summary collapse

Methods included from ActiveSupport::CoreExtensions::Hash::Except

#except, #except!

Methods included from ActiveSupport::CoreExtensions::Hash::Slice

#slice, #slice!

Methods included from ActiveSupport::CoreExtensions::Hash::Diff

#diff

Methods included from ActiveSupport::CoreExtensions::Hash::Conversions

included, #to_query, #to_xml

Methods included from ActiveSupport::CoreExtensions::Hash::ReverseMerge

#reverse_merge, #reverse_merge!

Methods included from ActiveSupport::CoreExtensions::Hash::DeepMerge

#deep_merge, #deep_merge!

Methods included from ActiveSupport::CoreExtensions::Hash::IndifferentAccess

#with_indifferent_access

Methods included from ActiveSupport::CoreExtensions::Hash::Keys

#assert_valid_keys, #stringify_keys, #stringify_keys!, #symbolize_keys, #symbolize_keys!

Instance Method Details

#to_json(options = {}) ⇒ Object

Returns a JSON string representing the hash.

Without any options, the returned JSON string will include all the hash keys. For example:

{ :name => "Konata Izumi", 'age' => 16, 1 => 2 }.to_json
# => {"name": "Konata Izumi", 1: 2, "age": 16}

The keys in the JSON string are unordered due to the nature of hashes.

The :only and :except options can be used to limit the attributes included, and will accept 1 or more hash keys to include/exclude.

{ :name => "Konata Izumi", 'age' => 16, 1 => 2 }.to_json(:only => [:name, 'age'])
# => {"name": "Konata Izumi", "age": 16}

{ :name => "Konata Izumi", 'age' => 16, 1 => 2 }.to_json(:except => 1)
# => {"name": "Konata Izumi", "age": 16}

The options also filter down to any hash values. This is particularly useful for converting hashes containing ActiveRecord objects or any object that responds to options in their to_json method. For example:

users = User.find(:all)
{ :users => users, :count => users.size }.to_json(:include => :posts)

would pass the :include => :posts option to users, allowing the posts association in the User model to be converted to JSON as well.


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# File 'lib/active_support/json/encoders/hash.rb', line 31

def to_json(options = {}) #:nodoc:
  hash_keys = self.keys

  if options[:except]
    hash_keys = hash_keys - Array(options[:except])
  elsif options[:only]
    hash_keys = hash_keys & Array(options[:only])
  end

  returning result = '{' do
    result << hash_keys.map do |key|
      "#{ActiveSupport::JSON.encode(key)}: #{ActiveSupport::JSON.encode(self[key], options)}"
    end * ', '
    result << '}'
  end
end