Using the Observer Pattern in Real Life
Ever move to a new place and try to remember all the places you've given your mailing address to so you can notify them about your new address? This happened to me recently and I found a pretty good solution to this problem originating from software engineering design patterns, particularly the Observer Pattern.
In the Observer Pattern, an Subject keeps track of a collection of Observers that it can notify when it's state changes. Observers register themselves with the Subject, indicating that they want to be notified when the Subject changes state. Then any time the Subject changes state, it will go through and notify all registered Observers.
It might seem obvious, but keeping track of a list of people and places you have given your mailing address so that you can notify them when they need to update their records is applying the Observer Pattern outside of the programming world.
To apply this pattern, create a text document named “mailing-address-observers.txt” and save it. Now any time you give your mailing address out (for example, to a magazine subscription, a bank, an insurance company, or your Grandma over the phone), make sure to register the observer by adding them to your observer list.
Now that you have a list of registered observers, any time you move you don't need to worry about who the hell has your old mailing address and how many packages are being sent to your old address. Just loop over your observers document and notify each one of your new address.