Ruby version of Javascript's with (See related posts)

A few different languages happily have a with block that basically calls unresolved methods on a particular object.

In Javascript, for example:

   1  
   2  with document
   3  {
   4      elt = getElementById( 'myElt' );
   5      appendChild( elt );
   6  }

Implementing a similar functionality in Ruby is stunningly simple:

   1  
   2  class Object
   3    def with_me( &block )
   4      instance_eval block
   5    end
   6  
   7    def with( object, &block )
   8      object.instance_eval &block
   9    end
  10  end

This gives us two syntaxes to work with. Assuming the same methods we saw above in Javascript are around in Ruby:

   1  
   2  with document do
   3      elt = getElementById( 'myElt' );
   4      appendChild( elt );
   5  end

or

   1  
   2  document.with_me do
   3      elt = getElementById( 'myElt' );
   4      appendChild( elt );
   5  end

The biggest issue with this is that it potentially breaks encapsulation, since calling private methods is perfectly possible in the block passed to #with or #with_me. Also significant, in Javascript the with block will call methods on the object if it can't resolve to local functions first; this code will do the opposite -- if it can't find the method in the object, it will try to find a function in the block's original enclosing scope.