Imagine you want to pass some value from your join function in channels to handle_in. You cannot simply assign to a variable:
def join(..., socket) do
username = "hello"
{:ok, socket}
end
def handle_in(..., socket) do
username #=> this will raise
end
So instead, we store it in a data-structure (or assign it to a data structure) and pass the data structure forward:
def join(..., socket) do
socket = assign(socket, :username, "hello")
{:ok, socket}
end
def handle_in(..., socket) do
socket.assigns.username #=> this works
end
The field in itself is a map with atom keys and the stored values.
