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 = Hash.new
h[:a] = 1
h[:a] # => 1
h['a'] # => nil
h.a # => NoMethodError: undefined method `a' for {}:Hash
require 'symboltable'
t = SymbolTable.new
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}"
end
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.
Why?
Mainly just for fun, and because I sometimes miss the automatic and ubiquitous type conversion you get in PHP.
Installation
Using RubyGems:
$ sudo gem install symboltable
From a local copy:
$ git clone git://github.com/mjijackson/symboltable.git
$ cd symboltable
$ rake package && sudo rake install