backbone.js sub routing

app.js

/* Pretend app setup stuff is here */

/* Kick off app */
jQuery(function($) {

  var Gallery = app.module("gallery");

  app.Router = Backbone.Router.extend({
    initialize: function() {
      this.gallery = new Gallery.Router("gallery/");
    }
  });

  // Actually initialize
  new app.Router();

});

gallery.js

(function(Gallery) {

  var Helper = app.module("helper");

  Gallery.Router = Helper.SubRoute.extend({
    routes: {
      "": "list",
      "add": "add",
      "filter": "filter"
    }
  });

})(app.module("gallery"));

helper.js

(function(Helper) {

  Helper.SubRoute = Backbone.Router.extend({
    constructor: function(prefix) {
      var routes = {};

      // Prefix is optional, set to empty string if not passed
      prefix = prefix || "";

      // Allow for optionally omitting trailing /.  Since base routes do not
      // trigger with a trailing / this is actually kind of important =)
      if (prefix[prefix.length-1] == "/") {
        prefix = prefix.slice(0, prefix.length-1);

      // If a prefix exists, add a trailing /
      } else if (prefix) {
        prefix += "/";
      }

      // Every route needs to be prefixed
      _.each(this.routes, function(callback, path) {
        if (path) {
          return routes[prefix + path] = callback;
        }

        // If the path is "" just set to prefix, this is to comply
        // with how Backbone expects base paths to look gallery vs gallery/
        routes[prefix] = callback;
      });

      // Must override with prefixed routes
      this.routes = routes;

      // Required to have Backbone set up routes
      Backbone.Router.prototype.constructor.call(this);
    }
  });

})(app.module("helper"));

I ended up logging an issue against @geekdave's repo at BackboneSubroute/backbone.subroute#4 - I'm not 100% sure everything is correct (it's a little handwavy, I'm under pressure to get something out the door blahblahblah so I had to move on), but I think that's the gist of things. Hopefully I'll have time to come back to it, if @geekdave isn't able to get to the bottom of it himself.

And how to dynamically remove the subroute?

@SamDecrock you can't without manipulating Backbone.history and allowing your application to have knowledge of all the paths that were added. This can be quite a complex procedure if you haven't built your application with an ability to get paths from individual subroutes. I tend to create wrapping objects that have an activate and deactivate method that are managed by a facade to a Backbone router.

considering that you have a list of paths (allRoutes in this example).

for (var path in allRoutes) {
    var combinedPath = routerPrefix + '/' + path;

    // This removes all trace of the routes from the history
    Backbone.history.handlers = _.reject(
        Backbone.history.handlers, function(value) {
            return String.prototype.search.call(
                value.route, 
                combinedPath
            ) !== -1;
        }
    );
}

// Unfortunately, we still have a route in the history for the routerPrefix 
// (in fact we should have two, the one used by the primary router and
// one created by the sub router (the latter takes precedence as it has 
// been unshifted onto the handlers array. The next step therefore is to 
// get all the primary routes registered in the history.
var primaryHandlers = _.filter(Backbone.history.handlers, function(value) {
    return String.prototype.search.call(value.route, routerPrefix) !== -1;
});

// If the result has a length greater than 1 (this will be the case most of
// the time) then we need to remove the first one that was registered by 
// the subrouter, this leaves the primary route still available to start the 
// sub router again when it is needed. Else we want to keep the route as
// it was set by the primary router.
if (primaryHandlers.length > 1) {
    Backbone.history.handlers.splice(
        Backbone.history.handlers.indexOf(primaryHandlers[0])
    , 1);
}