Sometimes, we need access of some object /data/ variable globally throughout the App. In that case, creating a singleton class which can be accessed through out the app is helpful.
App Delegate is a good example of singleton class. After googling for 2 days, i found a cool way to create singleton class using Macros. Let's suppose i have to create an HttpRequest Manager to handle all requests using only one instance .
call following line where you have to want to create the singleton class object.