Class: Tins::Bijection

Inherits:
Hash show all
Defined in:
lib/tins/bijection.rb

Overview

A hash subclass that ensures bijection between keys and values

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Methods inherited from Hash

#subhash!

Methods included from Subhash

#subhash

Constructor Details

#initialize(inverted = Bijection.new(self)) ⇒ Bijection

The initialize method sets up a new instance with an inverted bijection.

a new Bijection instance

Parameters:

  • inverted (Bijection) (defaults to: Bijection.new(self)) —

    the inverted bijection object, defaults to



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# File 'lib/tins/bijection.rb', line 29

def initialize(inverted = Bijection.new(self))
  @inverted = inverted
end

Instance Attribute Details

#inverted ⇒ Bijection (readonly)

The inverted attribute returns the inverted state of the object. Creates a new Bijection instance filled with key-value pairs.

Returns:

  • (Bijection) —

    a new bijection instance with the specified key-value pairs



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# File 'lib/tins/bijection.rb', line 78

def inverted
  @inverted
end

Class Method Details

.[](*pairs) ⇒ Bijection

Creates a new Bijection instance with key-value pairs.

bijection

Parameters:

  • pairs (Array) —

    an array of key-value pairs to populate the

Returns:

  • (Bijection) —

    a new bijection populated with the provided pairs



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# File 'lib/tins/bijection.rb', line 10

def self.[](*pairs)
  pairs.size % 2 == 0 or
    raise ArgumentError, "odd number of arguments for #{self}"
  new.fill do |obj|
    (pairs.size / 2).times do |i|
      j = 2 * i
      key = pairs[j]
      value = pairs[j + 1]
      obj.key?(key) and raise ArgumentError, "duplicate key #{key.inspect} for #{self}"
      obj.inverted.key?(value) and raise ArgumentError, "duplicate value #{value.inspect} for #{self}"
      obj[pairs[j]] = pairs[j + 1]
    end
  end
end

Instance Method Details

#[]=(key, value) ⇒ Object

Note:

This method will not overwrite existing keys, it will return early

The []= method assigns a value to a key in the hash and maintains an inverted index.

if the key already exists.

Parameters:

  • key (Object) —

    the key to assign

  • value (Object) —

    the value to assign

Returns:

  • (Object) —

    the assigned value



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# File 'lib/tins/bijection.rb', line 68

def []=(key, value)
  key?(key) and return
  super
  @inverted[value] = key
end

#fill {|self| ... } ⇒ self

The fill method populates the object with content from a block if it is empty.

empty

Yields:

  • (self) —

    yields self to the block for population

Returns:

  • (self) —

    returns the object itself after filling or if it was not



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# File 'lib/tins/bijection.rb', line 39

def fill
  if empty?
    yield self
    freeze
  end
  self
end

#freeze ⇒ Object

The freeze method freezes the current object and its inverted attribute.

Returns:

  • (Object) —

    the frozen object



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# File 'lib/tins/bijection.rb', line 50

def freeze
  r = super
  unless @inverted.frozen?
    @inverted.freeze
  end
  r
end