Class: ActiveSupport::OrderedHash

Inherits:
Hash show all
Defined in:
lib/active_support/ordered_hash.rb

Overview

The order of iteration over hashes in Ruby 1.8 is undefined. For example, you do not know the order in which keys will return keys, or each yield pairs. ActiveSupport::OrderedHash implements a hash that preserves insertion order, as in Ruby 1.9:

oh = ActiveSupport::OrderedHash.new
oh[:a] = 1
oh[:b] = 2
oh.keys # => [:a, :b], this order is guaranteed

ActiveSupport::OrderedHash is namespaced to prevent conflicts with other implementations.

Direct Known Subclasses

OrderedOptions

Constant Summary

Constants inherited from Hash

Hash::DISALLOWED_XML_TYPES

Class Method Summary collapse

Instance Method Summary collapse

Methods inherited from Hash

#as_json, #assert_valid_keys, #deep_dup, #deep_merge, #deep_merge!, #diff, #encode_json, #except, #except!, #extract!, from_trusted_xml, from_xml, #reverse_merge, #reverse_merge!, #slice, #slice!, #stringify_keys, #stringify_keys!, #symbolize_keys, #symbolize_keys!, #to_param, #to_xml, #with_indifferent_access

Constructor Details

#initialize(*args, &block) ⇒ OrderedHash

In MRI the Hash class is core and written in C. In particular, methods are programmed with explicit C function calls and polymorphism is not honored.

For example, []= is crucial in this implementation to maintain the @keys array but hash.c invokes rb_hash_aset() originally. This prevents method reuse through inheritance and forces us to reimplement stuff.

For instance, we cannot use the inherited #merge! because albeit the algorithm itself would work, our []= is not being called at all by the C code.



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# File 'lib/active_support/ordered_hash.rb', line 68

def initialize(*args, &block)
  super
  @keys = []
end

Class Method Details

.[](*args) ⇒ Object 



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# File 'lib/active_support/ordered_hash.rb', line 73

def self.[](*args)
  ordered_hash = new

  if (args.length == 1 && args.first.is_a?(Array))
    args.first.each do |key_value_pair|
      next unless (key_value_pair.is_a?(Array))
      ordered_hash[key_value_pair[0]] = key_value_pair[1]
    end

    return ordered_hash
  end

  unless (args.size % 2 == 0)
    raise ArgumentError.new("odd number of arguments for Hash")
  end

  args.each_with_index do |val, ind|
    next if (ind % 2 != 0)
    ordered_hash[val] = args[ind + 1]
  end

  ordered_hash
end

Instance Method Details

#[]=(key, value) ⇒ Object 



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# File 'lib/active_support/ordered_hash.rb', line 103

def []=(key, value)
  @keys << key unless has_key?(key)
  super
end

#clear ⇒ Object 



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# File 'lib/active_support/ordered_hash.rb', line 174

def clear
  super
  @keys.clear
  self
end

#delete(key) ⇒ Object 



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# File 'lib/active_support/ordered_hash.rb', line 108

def delete(key)
  if has_key? key
    index = @keys.index(key)
    @keys.delete_at index
  end
  super
end

#delete_if ⇒ Object 



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# File 'lib/active_support/ordered_hash.rb', line 116

def delete_if
  super
  sync_keys!
  self
end

#each ⇒ Object 



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# File 'lib/active_support/ordered_hash.rb', line 160

def each
  return to_enum(:each) unless block_given?
  @keys.each {|key| yield [key, self[key]]}
  self
end

#each_key ⇒ Object 



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# File 'lib/active_support/ordered_hash.rb', line 148

def each_key
  return to_enum(:each_key) unless block_given?
  @keys.each { |key| yield key }
  self
end

#each_pair ⇒ Object 



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# File 'lib/active_support/ordered_hash.rb', line 166

def each_pair
  return to_enum(:each_pair) unless block_given?
  @keys.each {|key| yield key, self[key]}
  self
end

#each_value ⇒ Object 



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# File 'lib/active_support/ordered_hash.rb', line 154

def each_value
  return to_enum(:each_value) unless block_given?
  @keys.each { |key| yield self[key]}
  self
end

#encode_with(coder) ⇒ Object 



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# File 'lib/active_support/ordered_hash.rb', line 28

def encode_with(coder)
  coder.represent_seq '!omap', map { |k,v| { k => v } }
end

#extractable_options? ⇒ Boolean

Returns true to make sure that this hash is extractable via Array#extract_options!

Returns:

  • (Boolean) 


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# File 'lib/active_support/ordered_hash.rb', line 51

def extractable_options?
  true
end

#initialize_copy(other) ⇒ Object 



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# File 'lib/active_support/ordered_hash.rb', line 97

def initialize_copy(other)
  super
  # make a deep copy of keys
  @keys = other.keys
end

#inspect ⇒ Object 



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# File 'lib/active_support/ordered_hash.rb', line 212

def inspect
  "#<OrderedHash #{super}>"
end

#invert ⇒ Object 



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# File 'lib/active_support/ordered_hash.rb', line 208

def invert
  OrderedHash[self.to_a.map!{|key_value_pair| key_value_pair.reverse}]
end

#keys ⇒ Object 



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# File 'lib/active_support/ordered_hash.rb', line 132

def keys
  @keys.dup
end

#merge(other_hash, &block) ⇒ Object 



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# File 'lib/active_support/ordered_hash.rb', line 197

def merge(other_hash, &block)
  dup.merge!(other_hash, &block)
end

#merge!(other_hash) ⇒ Object Also known as: update 



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# File 'lib/active_support/ordered_hash.rb', line 186

def merge!(other_hash)
  if block_given?
    other_hash.each { |k, v| self[k] = key?(k) ? yield(k, self[k], v) : v }
  else
    other_hash.each { |k, v| self[k] = v }
  end
  self
end

#nested_under_indifferent_access ⇒ Object 



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# File 'lib/active_support/ordered_hash.rb', line 46

def nested_under_indifferent_access
  self
end

#reject(&block) ⇒ Object 



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# File 'lib/active_support/ordered_hash.rb', line 128

def reject(&block)
  dup.reject!(&block)
end

#reject! ⇒ Object 



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# File 'lib/active_support/ordered_hash.rb', line 122

def reject!
  super
  sync_keys!
  self
end

#replace(other) ⇒ Object

When replacing with another hash, the initial order of our keys must come from the other hash -ordered or not.



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# File 'lib/active_support/ordered_hash.rb', line 202

def replace(other)
  super
  @keys = other.keys
  self
end

#shift ⇒ Object 



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# File 'lib/active_support/ordered_hash.rb', line 180

def shift
  k = @keys.first
  v = delete(k)
  [k, v]
end

#to_a ⇒ Object 



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# File 'lib/active_support/ordered_hash.rb', line 144

def to_a
  @keys.map { |key| [ key, self[key] ] }
end

#to_hash ⇒ Object 



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# File 'lib/active_support/ordered_hash.rb', line 140

def to_hash
  self
end

#to_yaml(opts = {}) ⇒ Object 



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# File 'lib/active_support/ordered_hash.rb', line 32

def to_yaml(opts = {})
  if YAML.const_defined?(:ENGINE) && !YAML::ENGINE.syck?
    return super
  end

  YAML.quick_emit(self, opts) do |out|
    out.seq(taguri) do |seq|
      each do |k, v|
        seq.add(k => v)
      end
    end
  end
end

#to_yaml_type ⇒ Object 



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# File 'lib/active_support/ordered_hash.rb', line 24

def to_yaml_type
  "!tag:yaml.org,2002:omap"
end

#values ⇒ Object 



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# File 'lib/active_support/ordered_hash.rb', line 136

def values
  @keys.collect { |key| self[key] }
end