Powerful composition with Obviel data-render

Obviel is the client side web framework I've been hacking on for the past few years. It has among many other things a client-side template language called Obviel Template. Obviel Template has a bunch of nice features such as i18n support, about which I'll write more later. But the feature I want to talk about today is the data-render directive.

Obviel lets you define views for types of objects, and render them on elements. See my previous blog entry on the core of Obviel for a very short introduction to this concept (note: data-handler has been renamed to data-on). In web applications your Obviel views are mostly going to have small templates - each view doing its own thing: rendering a template for a model, handling user events, etc. Complex UIs are created by composing views together.

data-render is the tool that lets you do this easily from within a template. If we have the following model of a todo list:

{
  iface: 'todo-list',
  todos: [{ iface: 'todo-item', title: 'Item 1' },
          { iface: 'todo-item', title: 'Item 2' }]
}

Then we can create a view to render that todo-list like this:

obviel.view({
   iface: 'todo-list',
   obvt: '<ul><li data-repeat="todos" data-render="@."></li></ul>'
});

What, you may ask, is @.? It is Obviel Template's way to express "the current object", in this case the current item in the todos array that we are looping through using data-repeat.

And we also need to be able to render an individual todo-item:

obviel.view({
   iface: 'todo-item',
   obvt: '<div>{title}</div>'
});

Some benefits:

• each view is doing one and only one thing

• if todo-item has an event handler (for instance to handle click events), this will just work:

  obviel.view({
     iface: 'todo-item',
     obvt: '<div data-on="click|clicked">{title}</div>',
     clicked: function() {
       alert("You clicked!");
     }
  });

  [update: fixed bug in code example by renaming 'click' to 'clicked']

• The todo-list view is agnostic about what individual entries of the todos array actually are. So if you add a special-todo-item to the todos array, and provide a view for it, it will just work too. This is pretty powerful if you are going to hook up entirely different events in it!

Have fun with Obviel and see you next time!