Elixir GenServers are lightweight processes. GenServers provide a common interface for starting, stopping, and passing messages to and from. What you do from there is up to you.

GenServer processes can be adorned with custom behavior. This is done using basic Elixir modules that use GenServer.

Write a public interface for the client using basic methods. Then, write the internal handlers, using handle_cast and handle_call.

Resources

• https://elixircasts.io/intro-to-genserver
• https://github.com/elixircastsio/012_introduction_to_genserver/blob/master/shopping_list.ex

Try it out

```

Start the GenServer and grab its PID (process ID)

{:ok, pid} = ShoppingList.start_link()

Add milk, cheese, and eggs to the list

ShoppingList.add(pid, "milk") ShoppingList.add(pid, "cheese") ShoppingList.add(pid, "eggs")

View the list

ShoppingList.view(pid)

Remove cheese from the list

ShoppingList.remove(pid, "cheese")

View the updated list

ShoppingList.view(pid)

```