So I have been using Rails for quite some time but it was only today that I get to use the after_initialize callback. This is called everytime an ActiveRecord object is initialized (eg. when fetched from the database or when called with the new constructor)

The requirement was to move default value of a model which was previously set from the database into a constant in order to make it easier to change. Here is how my solution looked like(this is not actual code but it is algorithmically same)

{% gist lyc4n/b53b91258f966ef118081204c9e084b0 foo.rb %}

Notice above the use of self keyword. The reason behind this is that setters and getters in rails are actually methods. So here we actually have a def bar= that we would like to be invoked. Removing the self in the code above would make Ruby assume that bar is a local variable.