Module: Dbd::Helpers::OrderedSetCollection

Includes:
Enumerable
Included in:
Fact::Collection, Resource
Defined in:
lib/dbd/helpers/ordered_set_collection.rb

Overview

Transforms the mixing class into an OrderedSet.

On the mixing class, enumerable functions are possible, looping over the set in O(n), but it is not intended that the mixing class allows arbitrary access into the collection.

The add_and_return_index module method allows to get an index to an added element, so indexes can be built to access elements in O(1). The mixing class should not expose this index to the added element in it’s public API. The goal is to allow other implementations (e.g. with Hadoop, Neo4j, …) with the same API.

Class Method Summary collapse

Instance Method Summary collapse

Class Method Details

.add_and_return_index(element, collection) ⇒ Integer

Adds an element at the end of the collection and returns the array index of that element.

This is not an instance method to avoid it ending up in the public API of classes that mixin this module.

The implementation to find the index of the inserted element with ‘rindex` is primitive, but I did not see a better way in Ruby to do this (using `size` would certainly be not thread safe, maybe the current approach is thread safe, but that is not tested).

Returns:

  • (Integer) —

    index



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# File 'lib/dbd/helpers/ordered_set_collection.rb', line 79

def self.add_and_return_index(element, collection)
  collection << element
  collection.rindex(element)
end

Instance Method Details

#<<(element) ⇒ Object

Inserts an element at the end of the collection. Returns self to allow chaining.

Parameters:

  • element (Object)

Returns:

  • (Object) —

    self



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# File 'lib/dbd/helpers/ordered_set_collection.rb', line 35

def <<(element)
  @internal_collection << element
  self
end

#each ⇒ Object

For the Enumerable functionality.



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# File 'lib/dbd/helpers/ordered_set_collection.rb', line 42

def each
  @internal_collection.each do |e|
    yield e
  end
end

#freeze ⇒ Object 



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# File 'lib/dbd/helpers/ordered_set_collection.rb', line 84

def freeze
  @internal_collection.freeze
  self
end

#initialize ⇒ Object

Creates @internal_collection in the mixing class.



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# File 'lib/dbd/helpers/ordered_set_collection.rb', line 25

def initialize
  @internal_collection = []
  super
end

#last ⇒ Object

This is required as an efficient way to find the last element without stepping through the entire collection. This implementation is probably not thread safe.

Returns:

  • (Object) —

    the last element



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# File 'lib/dbd/helpers/ordered_set_collection.rb', line 53

def last
  @internal_collection.last
end

#size ⇒ Object

This is required as an efficient way to find the size without stepping through the entire collection. This implementation is probably not thread safe.

Returns:

  • (Object) —

    the last element



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# File 'lib/dbd/helpers/ordered_set_collection.rb', line 62

def size
  @internal_collection.size
end