Class: Hashery::Association

Inherits:
Object show all
Includes:
Comparable
Defined in:
lib/hashery/association.rb

Overview

Note:

This class is still fairly experimental. And it is not loaded along with the other Hashery libraries when using ‘require ’hashery’‘. It must be required independently.

Associations can be used to draw simple relationships.

:Apple >> :Fruit
:Apple >> :Red

:Apple.associations #=> [ :Fruit, :Red ]

It can also be used for simple lists of ordered pairs.

c = [ :a >> 1, :b >> 2 ]
c.each { |k,v| puts "#{k} associated with #{v} }

produces

a associated with 1
b associated with 2

The method :>> is used to construct the association. It is a rarely used method so it is generally available. But you can’t use it for any of the following classes becuase they use #>> for other things.

Bignum
Fixnum
Date
IPAddr
Process::Status

Association is a general binary association that allows one object to be associated with another. It has a variety of uses, such as linked-lists, simple ordered maps and mixed collections, among them.

Defined Under Namespace

Modules: Kernel

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(index, value = nil) ⇒ Association

Initialize new Association.

Parameters:

  • index —

    The “index key” of the association.

  • value (defaults to: nil) —

    The “value” of the association.



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# File 'lib/hashery/association.rb', line 94

def initialize(index, value=nil)
  @index = index
  @value = value

  unless index.associations.include?(value)
    index.associations << value
  end
end

Instance Attribute Details

#index ⇒ Object

The “index key” of the association.



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# File 'lib/hashery/association.rb', line 81

def index
  @index
end

#value ⇒ Object

The “value” of the association.



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# File 'lib/hashery/association.rb', line 86

def value
  @value
end

Class Method Details

.[](index, value) ⇒ Object

Shortcut for #new.

Parameters:

  • index —

    The “index key” of the association.

  • value —

    The “value” of the association.

Returns:

  • ‘Association`.



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# File 'lib/hashery/association.rb', line 65

def [](index, value)
  new(index, value)
end

.reference ⇒ Object

Store association references.

Returns:

  • ‘Hash` of all associaitons.



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# File 'lib/hashery/association.rb', line 53

def reference
  @reference ||= Hash.new{ |h,k,v| h[k]=[] }
end

Instance Method Details

#<=>(assoc) ⇒ Integer

Compare the values of two associations.

Parameters:

  • TODO: —

    Comparions with non-associations?

  • assoc —

    The other ‘Association`.

Returns:

  • (Integer) —

    Returns Integer ‘1`, `0`, or `-1`.



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# File 'lib/hashery/association.rb', line 112

def <=>(assoc)
  return -1 if self.value < assoc.value
  return  1 if self.value > assoc.value
  return  0 if self.value == assoc.value
end

#inspect ⇒ String

Produce a literal code string for creating an association.

Returns:

  • (String) —

    Returns String.



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# File 'lib/hashery/association.rb', line 143

def inspect
  "#{index.inspect} >> #{value.inspect}"
end

#invert! ⇒ Array

Invert association, making the index the value and vice-versa.

Returns:

  • (Array) —

    Returns Array with two-elements reversed.



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# File 'lib/hashery/association.rb', line 123

def invert!
  temp = @index
  @index = @value
  @value = temp
end

#to_ary ⇒ Array

Convert to two-element associative array.

Returns:

  • (Array) —

    Returns Array Two-element Array of index and value pair.



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# File 'lib/hashery/association.rb', line 152

def to_ary
  [index, value]
end

#to_s ⇒ String

Produce a string representation.

Returns:

  • (String) —

    Returns String.



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# File 'lib/hashery/association.rb', line 134

def to_s
  return "#{index} >> #{value}"
end