Declarative hierarchical router for Polymer Dart 1.0. Use it like this:

	<a href="#/amazing/stuff">show me amazing stuff</a>
	<a href="#/amazing/features">show me amazing features</a>

	<fnx-router route="amazing">
		<fnx-router route="stuff">
		<fnx-router route="features">
			<h1>no way!</h1>

See examples.

Comes in with handy Polymer @bahavior which you can use to make any of your elements routing capable.

Note: Work in progress, I'll continue to develop this package as I use it in our Polymer projects.


The purpose of this package is to allow you to show/hide your elements depending on window.location.hash value. Every element with FnxRouterBehavior has route attribute and becomes subject of routing.

<fnx-router route='user'>
	<my-cool-element route='edit'>

Elements create a tree hierarchy of routing nodes (subtree of DOM, if you want). Their absolute route depends on route of their parents (and recursively up to the root element).

<fnx-router> <!-- this is a routing root and it has no
                  "route" attribute , it will be visible always -->
	<!-- visible on #/amazing -->	                  
	<fnx-router route="amazing"> 
		<!-- visible on #/amazing/stuff -->
		<fnx-router route="stuff"> 
			<!-- visible on #/amazing/stuff/vol1 -->			
			<fnx-router route="vol1"> 

Level separator / is a constant provided by fnx_router.


Your user can navigate through your app by simply changing location anchor:

<a href="#/amazing/stuff">show me amazing stuff</a>
<a href="#/amazing/features">show me amazing features</a>

However - this requires you to know the absolute path (absolute route) to the element, which is not very practical - hierarchical routing then loses it's purpose. There are several other ways how to navigate.

	<a href="#" data-router="#/amazing">open amazing menu</a>

	<fnx-router route="amazing">
		<a href="#" data-router="./stuff">stuff</a>			
		<a href="#" data-router="./features">features</a>			
		<a href="#" data-router="../regular">show regular</a>
		<fnx-router route="stuff">
		<fnx-router route="features">
			<h1>NO WAY!</h1>
	<fnx-router route="regular">
		This is pretty regular. Go see
		<a href="#" data-router="../amazing">something amazing</a>.			

All routing nodes listen for tap event (@Listen("tap")). If the event's target contains data-router attribute, tap event is canceled and processed by router (actual href or other default action is ignored). Possible values of data-router are:

  • #/something - absolute path to required element
  • ./something - relative path to this element's child
  • ../something - relative path to this element's siblink (only single ../ is supported for now, you cannot double-dot your path all the way up like ../../)

Your data-router value must start with either #/, ./ or ../.

<a href="#" data-router="./baby-boy">pictures of my boy</a>	
<a href="#" data-router="./baby-girl">pictures of my girl</a>	
<a href="#" data-router="../my-dumb-brother">pictures of my brother</a>

You can also change the route programmatically, see dartdoc.

fnx-router element

fnx_router package contains <fnx-router> element. It's a simple display: block; element which you can use instead of your regular <div>.

Specify dependency in pubspec.yaml:

  fnx_router: ^0.2.1

Run pub get, import it in your html:

<link rel="import" href="packages/fnx_router/fnx_router.html">

... and in your "index.dart" (or whatever is the name of your main script):

import 'package:fnx_router/fnx_router.dart';

Note: Importing this element in dart shouldn't be necessary, it seems like a Polymer bug to me. Or maybe I'm doing something wrong. I'm working on it.


FnxRouterBehavior toggles two boolean attributes on your element during routing:

  • route-visible
  • route-invisible

Use those attributes to hide your elements however you want:

	fnx-router[route-invisible] {
		display: none;
	.show-ghosts fnx-router[route-invisible] {
		opacity: 0.2;

Note: It's discouraged to remove elements from DOM tree, see polymer-dart wiki, that's one of the reasons we leave handling invisible elements up to you.

To prevent FUOC, add router-not-initialized to body element and style it:

	body[router-not-initialized] {
		opacity: 0;

After successful initialization, fnx_router exchanges this attribute for router-initialized.

Routing parameters

It would be nice to have routes like this: /user/1234/edit, but in current state of Polymer it would be difficult to create such link. Polymer doesn't (support expressions)https://github.com/Polymer/polymer/issues/1847 at this moment, so you cannot write href="/user/{{user.id}}/edit".

Because of this, your routes should be "hardwired constants" and everything what changes, should be provided via parameters.

<a href="#/my/hardwired/route;3.1415;another-parameter">go for PI</a>

You still cannot render href="#/my/hardwired/route;{{currentValueOfPI}};another-parameter", but you can use additional data-router attributes:

<a href="#"
	>go for PI</a>

Note: Routing parameters are simply a List<String> at this point.

Using router in your elements

fnx-router element is really just a smarter div. You will probably need to fetch data from API whenever your element becomes visible etc. Good news - thanks to Polymer behaviors, it's can be done really easy.

Enhance your element with FnxRouterBehavior like this:

In your template:

<!-- new attribute -->
<dom-module id="my-smart-rest-element" attributes="route">

In your class:

/* new behavior */
class MySmartRestElement extends PolymerElement with FnxRouterBehavior {

And add a callback for visibility changes:

void routeChanged(
	bool routeVisible,
	List<String> params,
	bool visibilityChanged) {
	if (visible) { foo(); } else { bar(); }

It cannot be easier! routeChanged callback will be invoked each time when:

  • your element is invisible and should become visible
  • your element is visible and should become invisible
  • your element is visible, should stay visible, but params changed (see Routing parameters above)
  • your element is visible, should stay visible, but absolute route changed

Use argument visibilityChanged to decide whether your visibility actually changed, or you are just being notified about some other change.

if (visible && visibilityChanged) {
if (!visible && visibilityChanged) {


With FnxRouterBehavior your element has access to:

// current state of visibility
bool routeVisible = false;

// last routing parameters
List<String> routerParams = [];

// absolute route to the parent element (/amazing)
String absoluteParentRoute = null;

// absolute route to this element (/amazing/stuff)
String absoluteRoute = null;

... and some methods for navigation, see dartdoc.

Notes, details and TODOs

Routing rules for element are evaluated in attached() Polymer lifecycle method and cannot be changed later.

fnx-router works only with shady DOM.


Feel free to contact me at <user-element>tomucha</user-element><host-element separator="@">gmail.com</host-element>, or fill-in a bugreport on Github issue tracking.



Routing behavior for Polymer elements.


Simple element with FnxRouterBehavior.