Browsing the blog archives for August, 2014.

A Template for Lunches

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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.

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A Picture is Worth 1000 Lies

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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.

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