Class: Vitae::OrderedHash

Inherits:
Hash
  • Object
show all
Defined in:
lib/vitae/ordered_hash.rb

Overview

This OrderedHash class was stolen from ActiveSupport. 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. Vitae::OrderedHash implements a hash that preserves insertion order, as in Ruby 1.9:

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

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

Class Method Summary collapse

Instance Method Summary collapse

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/vitae/ordered_hash.rb', line 47

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

Class Method Details

.[](*args) ⇒ Object 



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# File 'lib/vitae/ordered_hash.rb', line 52

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/vitae/ordered_hash.rb', line 82

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

#clear ⇒ Object 



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# File 'lib/vitae/ordered_hash.rb', line 141

def clear
  super
  @keys.clear
  self
end

#delete(key) ⇒ Object 



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# File 'lib/vitae/ordered_hash.rb', line 87

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/vitae/ordered_hash.rb', line 95

def delete_if
  super
  sync_keys!
  self
end

#each ⇒ Object Also known as: each_pair 



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# File 'lib/vitae/ordered_hash.rb', line 135

def each
  @keys.each {|key| yield [key, self[key]]}
end

#each_key ⇒ Object 



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# File 'lib/vitae/ordered_hash.rb', line 127

def each_key
  @keys.each { |key| yield key }
end

#each_value ⇒ Object 



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# File 'lib/vitae/ordered_hash.rb', line 131

def each_value
  @keys.each { |key| yield self[key]}
end

#initialize_copy(other) ⇒ Object 



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# File 'lib/vitae/ordered_hash.rb', line 76

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

#inspect ⇒ Object 



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# File 'lib/vitae/ordered_hash.rb', line 179

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

#invert ⇒ Object 



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# File 'lib/vitae/ordered_hash.rb', line 175

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

#keys ⇒ Object 



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# File 'lib/vitae/ordered_hash.rb', line 111

def keys
  @keys.dup
end

#merge(other_hash, &block) ⇒ Object 



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# File 'lib/vitae/ordered_hash.rb', line 164

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/vitae/ordered_hash.rb', line 153

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

#reject(&block) ⇒ Object 



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# File 'lib/vitae/ordered_hash.rb', line 107

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

#reject! ⇒ Object 



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# File 'lib/vitae/ordered_hash.rb', line 101

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/vitae/ordered_hash.rb', line 169

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

#shift ⇒ Object 



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# File 'lib/vitae/ordered_hash.rb', line 147

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

#to_a ⇒ Object 



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# File 'lib/vitae/ordered_hash.rb', line 123

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

#to_hash ⇒ Object 



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# File 'lib/vitae/ordered_hash.rb', line 119

def to_hash
  self
end

#to_yaml(opts = {}) ⇒ Object 



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

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

#to_yaml_type ⇒ Object

:nodoc:



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# File 'lib/vitae/ordered_hash.rb', line 20

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

#values ⇒ Object 



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# File 'lib/vitae/ordered_hash.rb', line 115

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