Multiple rest handlers in Cowboy

2
votes

Is there a simple way of setting up a single dispatch route in Cowboy that allows multiple handlers such as: /base/add_something /base/remove_something

and have each of those actions services by a single handler that can differentiate them? All of the examples seem to map 1 handler to 1 dispatch, I would like to consolidate functionality if possible.

2
resterlangcowboy

2 Answers

5
votes

You can do this:

Dispatch:

...
Dispatch = cowboy_router:compile(
             [{'_', [{"/base/:action", 
                      [{type,
                        function,
                        is_in_list([<<"add_something">>,
                                    <<"remove_something">>])}], 
                      app_handler, []}]}]),
...
is_in_list(L) ->
    fun(Value) -> lists:member(Value, L) end.
...

In app_handler.erl:

...
-record(state, {action :: binary()}).
...
rest_init(Req, Opts) ->
    {Action, Req2} = cowboy_req:binding(action, Req),
    {ok, Req2, #state{action=Action}}.
...
allowed_methods(Req, #state{action=<<"add_something">>}=State) ->
    {[<<"POST">>], Req, State};
allowed_methods(Req, #state{action=<<"remove_something">>}=State) ->
    {[<<"DELETE">>], Req, State}.
...

and so on.

1
votes

You can also try to use cowboy_rest like so:

content_types_accepted(Req, State) ->
   case cowboy_req:method(Req) of
     {<<"POST">>, _ } ->
       Accepted = {[{<<"application/json">>, post_json}], Req, State};
     {<<"PUT">>, _ } ->
       Accepted = {[{<<"application/json">>, put_json}], Req, State}
   end,
Accepted.