Back in Chapter 13, when we built the reminder application, I mentioned that we could notify clients, whether by instant messaging, email, or some other method. In Chapter 15, our trading system used
io:format/2 to notify people of what was going on.
You can probably see the common link between these cases: They’re all about letting people (or some process or application) know about an event that happened at some point in time. In one case, we output only the results; in the other, we took the pid of subscribers before sending them a message.
This chapter covers the OTP event handlers, one of the many strategies to handle notifications. After reviewing the handlers, we will put this knowledge in practice by implementing ...