Programming Erlang, 2nd Edition

Getting Started with gen_server

I’m going to throw you in at the deep end. Here’s the simple three-point plan for writing a gen_server callback module:

1. Decide on a callback module name.

2. Write the interface functions.

3. Write the six required callback functions in the callback module.

This is really easy. Don’t think—just follow the plan!

Step 1: Decide on the Callback Module Name

We’re going to make a simple payment system. We’ll call the module my_bank.

Step 2: Write the Interface Routines

We’ll define five interface routines, all in the module my_bank.

start()

Open the bank.

stop()

Close the bank.

new_account(Who)

Create a new account.

deposit(Who, Amount)

Put money in the bank.

withdraw(Who, Amount)

Take money out, if in credit.

Each of these ...