In my rails model, I have a decimal property called employer_wcb. I would like it if, when employer_wcb was changed, a dirty bit was set to true. I'd like to override the employer_wcb setter method. Any way to do so (in particular using metaprogramming)?
So actually, as of Rails v2.1, this has been baked into Rails. Have a look at the documentation for ActiveRecord::Dirty. In summary:
# Create a new Thing model instance;
# Dirty bit should be unset...
t = Thing.new
t.changed? # => false
t.employer_wcb_changed? # => false
# Now set the attribute and note the dirty bits.
t.employer_wcb = 0.525
t.changed? # => true
t.employer_wcb_changed? # => true
t.id_changed? # => false
# The dirty bit goes away when you save changes.
t.save
t.changed? # => false
t.employer_wcb_changed? # => false