Skip to content
This repository


Subversion checkout URL

You can clone with HTTPS or Subversion.

Download ZIP

A Symbols-only Hash for Ruby

branch: master

SymbolTable is a handy little Ruby class that was conceived from the union of Hash and Symbol. SymbolTable directly extends Hash, but it stores all keys internally as symbols. Any key that cannot be converted to a Symbol is not valid.

While this may seem restrictive, it does have the nice side effect of making all keys slightly more memorable and usable. For example, values may be set and retrieved using any key that resolves to the same symbol.

h =
h[:a] = 1
h[:a]       # => 1
h['a']      # => nil
h.a         # => NoMethodError: undefined method `a' for {}:Hash

require 'symboltable'

t =
t[:a] = 1
t[:a]       # => 1
t['a']      # => 1
t.a         # => 1
t.b = 2     # => 2

Also, because SymbolTable subclasses Hash, you get all the nice methods of Hash for free.

t.keys      # => [:a, :b]
t.values    # => [1, 2]

t.merge!('c' => 3, :d => 4)
t.keys      # => [:a, :b, :c, :d]
t.values    # => [1, 2, 3, 4]

t.each do |k, v|
  puts "#{k} = #{v}"

You get the idea. This kind of data structure is mainly useful for large configuration objects and the like, where you want to store a bunch of data and you don't want to have to remember later how you stored it.


Mainly just for fun, and because I sometimes miss the automatic and ubiquitous type conversion you get in PHP.


Using RubyGems:

$ sudo gem install symboltable

From a local copy:

$ git clone git://
$ cd symboltable
$ rake package && sudo rake install


Copyright 2012 Michael Jackson

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

The software is provided "as is", without warranty of any kind, express or implied, including but not limited to the warranties of merchantability, fitness for a particular purpose and non-infringement. In no event shall the authors or copyright holders be liable for any claim, damages or other liability, whether in an action of contract, tort or otherwise, arising from, out of or in connection with the software or the use or other dealings in the software.

Something went wrong with that request. Please try again.