router is an in-memory trie based path router for Erlang. It can be used to route paths to destinations. It has single-level, and multi-level wildcard levels.

It can be used for arbitrary path/hierarchical based routing, and you can have multiple independent routers.

Create a new router like this:

   Router = router:new()

This creates multiple ets tables which are owned by the calling process. It is advised to call this inside a gen_server.

Now you can add routes like this:

   router:add(Router, [<<"a">>, <<"b">>], MyDestination),
   ...

This creates a route from path <<"a">>, <<"b">> to the information inside MyDestination. It is important that routes are added synchronized. It is best to do it inside a handle_call or handle_cast of a single gen_server.

After this it is possible to route request paths to destinations:

  Routes = router:route(Router, [<<"foo">>, <<"bar">>]),
  ...

Calls to route can be called in parallel.

Router has two different wildcards, multi-level and single-level wildcards.

The following wildcards are implemented:

• '+', matches one level on the path.
• {'+', test}, matches one level on the paths and binds the path element to test.
• {'+', test, {module, function}}, matches the element on the path if the call to module:function(PathElement) returns true.

There is one multi-level wildcard '#' which matches all elements on the path.

Example single-level wildcard route:

   router:add(Router, [<<"rsc">>, {'+', id}], {controller_rsc, [{foo, <<"bar">>]})

When you now call router:route(Router,[<<"rsc">>, <<"12312">>]), you get a list with route tuples with all matching destinations and the list of bound variables in a proplist. In this case: [{route, {controller_rsc, [{foo, <<"bar">>}]}, [{id, <<"12312">>}].

You get a list of matching destinations, and all elements which are bound in a proplist as result.

Example multi-level wildcard route:

    router:add(Router, [<<"truck">>, <<"00001">>, '#'], self())

This will match all routes to [<<"truck">>, <<"00001">>] and all its sub paths. For example: [<<"truck">>, <<"00001">>, <<"temperature">>] will match and also [<<"truck">>, <<"00001">>, <<"location">>].