class_eval(...) public

Evaluates the string or block in the context of mod. This can be used to add methods to a class. module_eval returns the result of evaluating its argument. The optional filename and lineno parameters set the text for error messages.

   class Thing
   end
   a = %q{def hello() "Hello there!" end}
   Thing.module_eval(a)
   puts Thing.new.hello()
   Thing.module_eval("invalid code", "dummy", 123)

produces:

   Hello there!
   dummy:123:in `module_eval': undefined local variable
       or method `code' for Thing:Class
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