Browsing the archives for the EmberJs tag.

A Template for Lunches

work safe

If you want to show anything on your page, you’re going to have to write a template. A template is the html to display on each page view. And if you use resources, they nest! Ember, by default, uses the Handlebars template engine.

Lunchtime!

It’s a Friday and I want ribs for lunch. But I don’t want to go alone. I’ll just write an intranet app that lets me invite a few coworkers to lunch. Because email is hard.

Begin at the beginning.

The default template is the application template. you can tell it’s the application because it doesn’t have a name. The application template is used to lay out the main page structure and all the site branding. all other templates are nested inside and show up where the {{outlet}} tag is used.

<br/>
<script type="text/x-handlebars">  
<h1>Lunch-o-Matic!</h1>  
<div class="subtext">Meet your coworkers for lunch</div>  
{{outlet}}  
</script><br/>

But, that alone isn’t very interesting, is it?

Okay, lets start off by managing some expectations. I’ll cover Controllers next week, but I’ll be mentioning them often. About 1/2 of the cool things about templates have some counterpart in the controller supporting them. That said, I’m getting hungry. Let’s gather up the team and head out for Barbecue!

I Decide who Leaves and who Dines!

I need to display a list of my coworkers so I can pick a couple of them.

<br/>
<script type="text/x-handlebars" data-template-name="lunchPicker">  
<h2>Who's in?</h2>  
{{input value=lunchType placeholder="What's for Lunch"}}  
<table><tr><th>invite?</th><th>name</th><th>email</th></tr>  
{{#each employee in employees}}  
  {{#if employee.isAvailable}}  
    <tr><td>{{input type="checkbox" checked=employee.isSelected}}</td>  
        <td>{{employee.fullName}} ({{employee.initials}})</td>  
        <td>{{employee.email}}</td>  
    </tr>  
  {{/if}}  
{{/each}}  
</script><br/>

A few things to note in the above example. I’m using an {{input}} block to make a text field that binds to the controller property lunchType. That will be used to let everyone know what kind of food we’re going to eat! Next, I’m looping over the a list of employees using an {{#each}} block. The collection comes from another controller property. Each element is then scoped as ‘employee’ inside the each block. I can conditionally skip displaying an employee if they are not available. more correctly, I can use an {{#if}} block to show only the available employees. I display a checkbox using a built in helper, {{input}}. It binds the checked state of the input control to the isSelected property of the employee. The last three are simple data bindings to text. They just forward properties from the model to html.

The Web Without Links isn’t the True Web.

Let’s tweak the employee listing. I want to make the name link to their info page. I can use the {{link-to}} block.

<br/>
...
<br/>
 <tr><td>{{input type='checkbox' checked=employee.isSelected}}</td><br/>
 <td>{{link-to 'employee' employee.employee_id}}<br/>
 {{employee.fullName}}<br/>
 {{/link-to}}<br/>
 ({{employee.initials}})</td><br/>
 <td>{{employee.email}}</td><br/>
...<br/>

But we need to DO something!

Wonderful! Things are moving right along. Now, how do I submit my selections? With an action! An action is a function in the controller. I promise, we will get to that later. Just trust me when I say our bindings put all the information in the model, so we don’t need to pass anything to the function. We just need to bind the action to a button, right after the end of our {{#each}} block.

<br/>
...
<br/>
<button {{action 'pickThem'}}>Choose these Coworkers</button><br/>

We can pass parameters in to the function, but we don’t need to at this time. In addition, we don’t have to worry about controlling event propagation or target a different controller. All of these are possible, just not necessary for us.

Your Bill Comes with Mints

There are a few things we can do to help us clean up our code from here.

Helper isn’t just for Hamburgers

A helper is a function that gets called like a block. It returns text to be displayed in the Html. If you need to format dates, for example, or want to display an employee’s spark-line for their time on the tread mill in the past two weeks.

Partials

Partials are templates that can be reused. They bind to what ever model or controller is in the context, just incase your data doesn’t look like you expected because you named something slightly wrong.

Views

A view can pick it’s own template. It has a bit more logic, but I’ wouldn’t go crazy building complex controls with them. In a couple weeks, we’ll cover Components and then we’ll go nuts.

1 Comment

A Picture is Worth 1000 Lies

work safe

Last week, I wrote about Routing in EmberJS. And I kinda lied a bit. I laid out the Pokédex route like this …

<br/>
App.router.map(function(){<br/>
 this.route("pokedex", {path: '/pokedex/:poke_id'});<br/>
});<br/>

That’s probably the wrong choice, but I made it for Pedagogical reasons. I regret nothing, but we are going to play with the routes of an example application to think through some design decisions and pick up a small detail of the router I overlooked. Resources.

A Picture is worth 1000 words

I’m a Father, Husband, etc. That means we are generating Gigabytes of pictures. Some are even in focus. She’s two, and fast. So, we are going to build a photo sharing site! Let’s give it a classy name. I’m thinking Phlickr. Um, legal informs me that’s a bit too similar some other upstart.

Introducing PhotoAlbum

PhotoAlbum is the latest in picture sharing technology. Some of our neat features are:

  • Friends
  • Albums
  • Tags
  • Favorites
  • Popular Pictures
  • Searching
  • Dashboard

Laying the Groundwork

I’m going to start by giving some examples of pages and their Urls.

  • Index – ‘/’
  • Login – ‘/login’
  • Dashboard – ‘/dashboard’
  • Popular Pictures – ‘/popular’
  • My Friends – ‘/friends’
  • Search – ‘/search/’
  • Tags – ‘/tags/’
  • Tag – ‘/tag/Sunny%20Days’
  • My Page – ‘/U/Brian’
  • Viewing My Album – ‘/U/Brian/album/sketchnotes’
  • My Albums – ‘/U/Brian/albums’
  • Creating a new album – ‘/U/Brian/albums/new’
  • My Friends Albums – ‘/U/Matt/albums’
  • A Photo – ‘/U/Brian/photo/24153′
  • My Photos – ‘/U/Brian/photos’
  • Uploading a photo – ‘/U/Brian/photos/new’

Cartography in Code (Making a Map)

Router.map(function() {
 this.route('login');
 this.route('dashboard');
 this.route('popular');
 this.route('friends');
 this.route('search');
 this.route('tags');
 this.route('tag', {path: '/tag/:tagname'});
   this.resource('posters', {path: '/U'}, function(){
     this.resource('user', {path: '/:username'}, function(){
       this.route('album', {path: '/album/:albumname'});
       this.resource('albums', function(){
         this.route('new');
       });
       this.route('photo', {path: '/photo/:photo_id'});
       this.resource('photos', function(){
         this.route('new');
       });
     });
   });
});

What’s the Difference?

Routes are for individual pages. Routes cannot be nested. If we want nested pages, we use resources. And resources give us a few new defaults.

Defaults

By default, the router gives us the route named ‘index’. And that in turn builds the controller, route, and loads the template named ‘index’. A resource is like a mini router in that way. If we name a resource ‘posters’, then all the child routes are prefixed with the name, including a new default ‘index’. The tetrad is listed out below. When deeply nested, only the resource and route matter for naming as opposed to the parent resources. Example, the template for the new albums is ‘albumsNew’ despite the albums resource being a child of the user resource.

  • RouteName – postersIndex
  • Controller – PostersIndexController
  • Route – PostersIndexRoute
  • template – postersIndex

Chains

The defaults are not the only things. They nest, just like applications. The posters resource looks for a template named ‘posters’ and then the child template. While I won’t dwell too much templates now, remember when the application template had an {{outlet}}? Well, the ‘posters’ template can have an {{outlet}} as well. this allow the templates to nest.

But it’s not just the templates, the controllers nest as well. So the model and properties of a parent controller can be accessed by a child. And the routes nest. Each parent finishing before the child runs.

A Time to Choose

Of course we can use routes to describe everything here. I’m fairly sure. But we will have all kinds of issues with reuse. the nesting of controllers and routes gives us a sensible place to hang some code reuse. The really interesting thing is I chose my routes and resources strictly based on what Urls made sense, what parts belong to other pieces of information. For example, there is only one dashboard, yours. The login is also independent of other data. However, each photo album belongs to a user. Matt’s album Dinners I Made is totally different from my album Dinners I Made. And while a picture has a tag, the collection of tags is only useful when it belongs to the system as a whole, allowing me to find all the pictures tagged sunrise regardless of who posted it. Once again, it all comes down to following the Urls and letting them tell you all you need to know.

No Comments

Getting from Here to There

work safe

Where do we go from here? We begin with the Url. The history of the web is based around the URL and our ability to transition from one url to another. Ember is built around the Url.

You are a Web Developer if you build apps with Urls

- Tom Dale

Every view we want to represent in our application will be represented as a different Url. When we want to show a specific piece of data, we use a different Url. Want to modify how we are showing the screen, then we add data to the Ulr. This will allow us to Deep Link and share specific views and app state with colleagues and coworkers. This is how the Web has worked since the web began. And Below, we see how the Url communicates with Ember to make choices on what to show the browser.

Ember Url Structure

Ember’s Url Structure taken from the presentation mentioned above.

The Router

The router dissects the Url and chooses which Route, Controller, Model, and Template to compose, execute, and use the results for displaying to the screen. By default, you get an ‘index’ route for free. As if I went to http://example.com/, that would be the default index.

Baby-steps to Customization

I can specify just a route named ‘about’ and that will show an ‘about’ template that will use the path http://example.com/about without specifying that path.

App.Router.map(function(){
    this.route("about");
});

A Route With a Different Name, Would It Navigate as Sweet?

Lets say I have a dumb legacy Url (http://example.com/meet-the-team) I need to keep working. Because Urls are important. But I want my internal code to use clear names (about). I can specify the path used in the route mapping.

App.Router.map(function(){
    this.route("about", {path: '/meet-the-team' });
});

My Pokémans, let me show you them.

One more mapping to cover for now, before we start talking about the magic a route actually does. What if we want to show the same page, but vary the data based on part of the path? I have a super awesome collection of Pokémans, let me show you my favorite Squirtle. I keep him at http://www.example.com/pokedex/poke_1. I can specify part of the path to be a dynamic segment. The name of the dynamic segment will show up as a param in the Route code.

App.router.map(function(){
    this.route("pokedex", {path: "/pokedex/:poke_id"});
});

Spent All That Time Defining

It’s neat and all that I’ve just created a route with a dynamic segment. But I need to use that to actually do work. I can create a PokedexRoute and override it’s model creation!

App.PokedexRoute = Ember.Route.extend({
    model: function(params){
        return Ember.$.getJson('api/pokemon/' + params.poke_id);
    }
});

What’s a lifecycle?

There are so many hooks in the route that I can override. I can override the controller creation. I can specify a non-standard template. Oh, that might be fun! This is the BEST pokemans, so he needs a custom template.

App.PokedexRoute = Ember.Route.extend({
    renderTemplate: function(controller, model){
      if(model.name === "Squirtiepie") {
         this.render("pokedex_squirtle");
      } else {
        this.render('pokedex');
      }
    }
});

Odds and Ends

If your code is slow, because for example not tied to anything real and not to name names or anything you query exchange, you can create a template called ‘loading’. Or you an overload the loading behavior.

The same thing with handling errors.

Customizing the Base

You may notice that the Url ember gives you has a hash (#). You can pick the location strategy as one of the following three. If you don’t like the hash, you can use the ‘location’. If you’re running an app out of a page, you can use ‘none’. The ‘hash’ strategy is the default.

App.Router.reopen({
    location: 'history'
});

Transition Overrides

When you edit the Pokedex, you don’t want to update the data until the Pokemaster is finished with her entry and presses the submit button. But what if she clicks on a link to another page? We can intercept the transition and quit!

App.PokedexEditRoute = Ember.Route.extend({
    action: {
	    willTransition: function(transition){
			if(this.controller.get('formHasEdits') &&  confirm("Are you sure you want to throw away your changes?")){
				transition.abort();
			} else {
				return true;
			}
		}
	}
}	
});

We could also validate the input for correctness and prevent a transition if we found it necessary.

Redirecting

Let’s say you load a model and need to decide to redirect because any Pikachu needs to redirected to a list of rats. That jerk gets all the attention anyway.

App.PokedexRoute = Ember.Route.extend({
   afterModel: function(model, transition){
      if(model.get('type') ==='Pikachu'){
        this.transitionTo('rats');
      }
   }
});

You Are Here

The router is all about defining the transitions between your views. In all honesty, the next time I write a desktop application, I may have to write something like this. It’s super easy to manage and override just about any transition. It’s useful, flexible, and the heart and soul of your application.

2 Comments

Rise of the Tetrad

work safe

Ember has about six concepts that once you understand a bit will help you unlock the documentation and figure out how to develop your site. I have written before about not needing to fully understand ember before working on a project, but once you start getting your feet under you and need to branch out. My hope is that by the time you are done reading, you will have a roadmap to the Ember Guides and the Ember APIs.

Rise of the Tetrad

Ember uses naming conventions to tie together the four moving parts of an ember application; the Route Name, the Route, the Controller, and the Template.

The Route Name

When the route is defined like I did below, it is given a name. By default, the path mapped to the route is the same as the route. For example, the route below defines a route named “level1” and maps the url “/level1” to the route of the same name.

Route.map(function(){
 this.route("level1");
 ...
});

The Route

By default we are generating a route named App.Level1Route. If we want to change the behaviors of the route, which we will cover in more depth in a different post, we need to define our Route and provide it with some overrides. A common override is to provide some model data, like below

App.Level1Route = Ember.Route.extend({
 model: function(){
 return Ember.$.getJSON("http://mygame.com/api/level1.json");
 }
});

The Controller

Again by default, we have a controller called App.Level1Controller created for us. But if we want to override its behavior, we just make a new one with the correct name! For example, we can add an action to save the current state back to the server.

App.Level1Controller = Ember.Controller.extend({
 actions: {
 save: function(){
 Ember.$.postJSON("http://mygame.com/api/pause/", model);
 }
 }
});

The Template

We need to show screens for our level. This is done by showing a template. The default template is, of course, named ‘level1’. The template is written in handlebars.

<script type="text/x-handlebars" data-template-name="level1">
  <button {{action 'save'}}>save</button>
  <canvas name="game-level" width="500" height="400">
  </canvas>
</script>

Numbers are tricky. You said there were six, told us about four, but it looks more like only three.

Right. The Route, Controller, and Template are all based off of the Route’s Name. So, four for the price of three. The Other Fourth is the model. I’m just going to skip it for now. The three Ember apps I have written have not yet needed the complexity of an Ember Data model.

The other pieces you will come across are the Components, the views, and Router.

The Router

The router is the part that wires all the components together. We used it to set up our route mapping.

Views

Views let you add behavior to an html tag. You can add behaviors and event handlers to the tag.

Components

Components are an implementation of the W3C Custom Element Spec. They are far more functional than overriding an html tag, they are custom tags backed by a template and code that allow you to build custom controls. If you need a calendar control, start here. Need a tabbed page control? Check out Ember-Components.com for some examples.

Next Steps

Now that we know our way around the major concepts of the Ember framework, we can start to understand them one at a time. Maybe next time we will start with the routes.

No Comments

A quick note on EmberJs and ReactiveJS

work safe

I tweeted yesterday that I was having trouble with EmberJS and ReactiveJS integration.

Well, I figured it out! With some help from the fine ReactiveX folks.

The long story short is RxJs is smart about Ember, and there are consequences.

Yeah, it boiled down the the difference between mousedown and mouseDown. Did you catch the capitalization of the D? I never even thought to look…

So, what’s it look like in the end?

App.CanvasView = Ember.View.extend({
    tagName: 'canvas',
    didInsertElement: function(){
        this.subscription =
          Rx.Observable.fromEvent(this, 'mouseDown')
                       .subscribe(function(e){
                           console.log("x="+e.offsetX + " y="+e.offsetY);
                        });
    },
    willDestroyElement: function(){
        this.subscription.dispose();
    }
});

And now to start the magic of using RxJs.

COMPOSE ALL THE EVENTS

update

I still think there is one thing left. I’ll try and test it out and add a Pr in a bit, but it seems to be important for my situation.

If I look at line 124 and 125 of fromEvent.js, I see an unused argument. I passed that through to the ember listener calls.

    if (ember) {
      return fromEventPattern(
        function (h) { Ember.addListener(element, eventName, h); },
        function (h) { Ember.removeListener(element, eventName, h); },
        selector);
    }  

update 2

I submitted a pull request. I hope I’m right about this, or I’ll be beet-red.

1 Comment