caridy/template-registration.md

## template-registration.md

      
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              template-registration.md
            
          
    This gist was updated based on the discussion here : https://groups.google.com/forum/?fromgroups=#!topic/yui-contrib/cUpVvtoUBa8
Template Registration

With the ability to precompile templates into javascript and the abtraction layer provided by Y.Template to normalize the api to render those templates, we got one step closer to create applications that can be template language agnostic.
The premise here is to create a YUI Application that references templates by name and call for render when needed without having to know what engine to use, or what file generated the compiled template, or what api should be used for a particular template.
In order to facilitate this, we should have a centralized registration mechanism used by the application to register any template that is provisioned, in which case we can decouple the provisioning process from the actual rendering process.
Proposal

The initial proposal is to utilize Y.Template as the central hub for all those templates, and doing so by introducing three new static methods, register, unregister and render.
Register a template

To register a compiled template:
var revivedTemplate = Y.Template.register('templateName', template);

note: the revivedTemplate is probably the same as argument template, but just a guarantee that the function complies with the revive API in Y.Template.
note: the register method override any existing template with the same name. this will help with live updates in development mode.
Unregister a template

To unregister a template by name:
var wasRegisteredBool = Y.Template.unregister('templateName');

which returns a boolean in case you want to know if the template was previously registered.
Render a template

To render a registered template:
var html = Y.Template.render('templateName', data);

All together (in code):

var revivedTemplate = Y.Template.register('name', function (data) {
    return 'some string';
});
var someString = revivedTemplate({foo: 'foo'});

The means the function passed to register() should be a function which conforms to the above contract. It is up to the thing which precompiles it to encapsulate or close-over any underly template engine specifics.
var someString = Y.Template.render('name', {foo: 'foo'});
var wasRegisteredBool = Y.Template.unregister('name');

The example

A good example of this will be a nodejs application that uses YUI on the server side to precompile templates generating YUI Modules that can be use on-demand or required by our business logic, where those modules can do the provision of templates into the internal register, which guarantees that our business logic can render them. Some code:
Pre-compiled template into a module:
YUI.add('foo', function (Y, NAME) {
  var compiled = function (data) {
    /* compiled template */
    return '<html fragment>';
  };
  Y.Template.register('foo', compiled);
}, '', {requires: ['template-base']});

Where the business logic can require foo to guarantee the provision:
YUI.add('bar', function (Y, NAME) {
  var html = Y.Template.render('foo', {
    tagline: 'bar is now template language agnostic'
  });
}, '', {requires: ['foo']});

Few more notes


The internal cache mechanism should not be expensive
Y.Template._cache = {}; as the cache mechanism should be just fine.
Throwing when unregistered template is invoked
Y.Template.render vs Y.Template.prototype.render might be confused, we need to clearly state this in the docs.
The nature of the render method is syncrounous, hence any register template should be syncronous.