Question

While ruby does allow modifying any class at any place in the code, I was wondering if it was possible to create a sandbox like protected environment to run some third party code such that rest of the application code would be isolated from any arbitrary modifications to the pre-defined classes/ standard library classes.

Answer 1

You can play with Ruby’s safe levels:

http://www.ruby-doc.org/docs/ProgrammingRuby/html/taint.html

Here’s the description of safe level 4 and above:

Ruby effectively partitions the running program in two. Nontainted
objects may not be modified. Typically, this will be used to create a
sandbox: the program sets up an environment using a lower $SAFE level,
then resets $SAFE to 4 to prevent subsequent changes to that
environment.