nova_handlers (nova v0.9.1) View Source

This module is responsible for all the different return types a controller have. Nova is constructed in such way that it's really easy to extend it by using handlers. A handler is basically a module consisting of a function of arity 4. We will show an example of this.

If you implement the following module:

-module(my_handler). -export([init/0, handle_console]).

init() -> nova_handlers:register_handler(console, {my_handler, handle_console}).

handle_console({console, Format, Args}, {Module, Function}, State) -> io:format("~n=====================~n", []). io:format("~p:~p was called.~n", []), io:format("State: ~p~n", [State]), io:format(Format, Args), io:format("~n=====================~n", []), {ok, 200, #{}, EmptyBinary}.

The init/0 should be invoked from your applications supervisor and will register the module my_handler as handler of the return type {console, Format, Args}. This means that you can return this tuple in a controller which invokes my_handler:handle_console/4.

A handler can return two different types

{ok, StatusCode, Headers, Body} - This will return a proper reply to the requester.

{error, Reason} - This will render a 500 page to the user.

Link to this section Summary

Functions

Fetches the handler identified with 'Handle' and returns the callback function for it.
Registers a new handler. This can then be used in a nova controller by returning a tuple where the first element is the name of the handler.
Unregisters a handler and makes it unavailable for all controllers.

Link to this section Types

Specs

handler_callback() :: {Module :: atom(), Function :: atom()} | fun((...) -> handler_return()).

Specs

handler_return() ::
    {ok, State2 :: nova:state()} |
    {Module :: atom(), State :: nova:state()} |
    {error, Reason :: any()}.

Link to this section Functions

Specs

get_handler(Handle :: atom()) -> {ok, Callback :: handler_callback()} | {error, not_found}.
Fetches the handler identified with 'Handle' and returns the callback function for it.
Link to this function

register_handler(Handle, Callback)

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Specs

register_handler(Handle :: atom(), Callback :: handler_callback()) ->
                    ok | {error, Reason :: atom()}.
Registers a new handler. This can then be used in a nova controller by returning a tuple where the first element is the name of the handler.

Specs

start_link() ->
              {ok, Pid :: pid()} |
              {error, Error :: {already_started, pid()}} |
              {error, Error :: term()} |
              ignore.
Link to this function

unregister_handler(Handle)

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Specs

unregister_handler(Handle :: atom()) -> ok.
Unregisters a handler and makes it unavailable for all controllers.