's Blog

Object Like Hash

4.28.2013

"My crime is that of curiosity"

While I was going through the source code of camping this piece of code that gives you Object like Hash got my attention. Instead of using Hash['key'] it allows you to use Hash.key hence the name "Object Like Hash".

Code

class H < Hash
    def method_missing(m,*a)
          m.to_s=~/=$/?self[$`]=a[0]:a==[]?self[m.to_s]:super
      end

      undef id, type if ?? == 63
  end

Usage

olh = H.new
olh.key1 = 'value1'
olh.key2 = 'value2'

olh.key1 #=> 'value1'
olh.key2 #=> 'value2'

Explanation

H is our object like hash. It inherits from Hash. The interesting part lies in changing its method_missing method. What the complex looking one liner does is :

If the method contains = at the very end it is an assignment. So, calling

olh.key1= "value1" translates to olh["key1"] = 'value1'

Otherwise (when we call olh.key1) it returns olh["key1"].

You may be wondering what does this line do :

undef id, type if ?? == 63

Well it undef's id and type when it is not ruby 1.9 or higher. ?? == 63 returns true if it is not ruby 1.9.* or higher.

rubyhash