Question

How to check if instance variable value have changed?

For global variable there is a trace_var method
http://apidock.com/ruby/Kernel/trace_var

But I didn’t found any information how to do that with instance variables(or class one).

I didn’t use Rails.

Ruby 1.9.2.

Answer 1

The best approach might be to avoid accessing and manipulating the instance variable directly and instead go through an attr_accessor style interface.

This gives you the ability to do things like this:

def my_attr=(value)
  logger.debug("my_attr changed to #{value.inspect}")
  @my_attr = value
end