Class: MultiHash

Inherits:
Object
  • Object
show all
Defined in:
lib/multihash/multihash.rb

Overview

This class provides a very simple interface for a hash with multiple keys that reference the same value. This is convenient for lookup tables that have several mappings to a single value, without doing anything particularly gross with Array#include? lookups.

Constant Summary collapse

HASH_METHOD_WHITELIST = 
%w{[] assoc default default= empty? each each_key
each_pair each_value fetch keys select values_at}

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(original_hash = {}, immutable = true) ⇒ MultiHash

Initialize an immutable multihash with the provided hash as its source. For example, we might want to look up the nation which produces different types of cars:

MultiHash.new (
  %w{Honda Nissan} => :japan,
  %w{Ford Chrysler} => :us,
  'BMW' => :germany
)

a multihash, with arrays or single objects as keys.

Parameters:

  • original_hash (Hash<Array|Object, Object>) (defaults to: {}) —

    the hash to convert into



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# File 'lib/multihash/multihash.rb', line 30

def initialize(original_hash={}, immutable=true)
  @_hash = Hash.new(original_hash.default)
  @immutable = immutable

  groups = []

  original_hash.each do |orig_key, value|
    key_array = orig_key.is_a?(Array) && orig_key || [orig_key]
    groups << key_array
    key_array.each { |k| map_value(k, value) }
  end

  store_groups(groups) unless immutable?
end

Instance Attribute Details

#immutable ⇒ Object Also known as: immutable?

Returns the value of attribute immutable.



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# File 'lib/multihash/multihash.rb', line 6

def immutable
  @immutable
end

Class Method Details

.[](args) ⇒ Object 



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# File 'lib/multihash/multihash.rb', line 69

def self.[](args)
  MultiHash.new(Hash[args])
end

Instance Method Details

#grouped ⇒ Object 



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# File 'lib/multihash/multihash.rb', line 45

def grouped
  Hash[@_groups.values.map { |g| [g, self[g.first]] }]
end

#set(key, value) ⇒ Object Also known as: []= 



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# File 'lib/multihash/multihash.rb', line 49

def set(key, value)
  fail 'Cannot modify an immutable MultiHash!' if immutable?
  split_key_from_group(key)
  map_value(key, value)
end

#set_group(key, value) ⇒ Object 



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# File 'lib/multihash/multihash.rb', line 56

def set_group(key, value)
  fail 'Cannot modify an immutable MultiHash!' if immutable?
  @_groups[key].each { |k| map_value(k, value) }
end

#to_h ⇒ Object 



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# File 'lib/multihash/multihash.rb', line 61

def to_h
  @_hash
end

#values ⇒ Object 



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# File 'lib/multihash/multihash.rb', line 65

def values
  @_values ||= @_hash.values.uniq
end