marionette.templatecache/readme.md

Renderer which provides a cache for retrieving templates from script blocks in your HTML. This improved the speed of subsequent calls to get a template.

# Marionette.TemplateCache

The `TemplateCache` provides a cache for retrieving templates from script blocks
in your HTML. This improved the speed of subsequent calls to get a template.

## Documentation Index

* [Using the Renderer with Marionette](#using-the-renderer-with-marionette)
* [Basic Usage](#basic-usage)
  * [Clear All Templates from cache](#clear-all-templates-from-cache)
  * [Clear Specific Templates from Cache](#clear-specific-templates-from-cache)
* [Customizing Template Access](#customizing-template-access)
  * [Override Template Retrieval](#override-template-retrieval)
  * [Override Template Compilation](#override-template-compilation)

## Using the Renderer with Marionette

To use the TemplateCache renderer with Marionette you will want to use the
Marionette `setRenderer` interface:

```javascript
var TemplateCache = require('marionette.templatecache');
var Mn = require('backbone.marionette');

Mn.setRenderer(TemplateCache.render);
```

## Basic Usage

To use the `TemplateCache`, call the `get` method on TemplateCache directly.
Internally, instances of the TemplateCache class will be created and stored
but you do not have to manually create these instances yourself. `get` will
return a compiled template function.

```javascript
var TemplateCache = require('marionette.templatecache');

var template = TemplateCache.get("#my-template", {option: 'value'});
// use the template
template({param1:'value1', paramN:'valueN'});
```

Making multiple calls to get the same template will retrieve the template from
the cache on subsequence calls.

### Clear All Templates from Cache

You can clear one or more, or all items from the cache using the `clear` method.
Clearing a template from the cache will force it to re-load from the DOM (via
the `loadTemplate` function which can be overridden, see below) the next time it
is retrieved.

If you do not specify any parameters, all items will be cleared from the cache:

```javascript
var TemplateCache = require('marionette.templatecache');

TemplateCache.get("#my-template");
TemplateCache.get("#this-template");
TemplateCache.get("#that-template");

// clear all templates from the cache
TemplateCache.clear();
```

### Clear Specific Templates from Cache

To clear only specific templates from the cache, specify the jQuery selector
that was passed in `get` to your `clear` call:

```javascript
var TemplateCache = require('marionette.templatecache');

// Pre-load our cache
TemplateCache.get("#my-template");
TemplateCache.get("#this-template");
TemplateCache.get("#that-template");

// clear 2 of 3 templates from the cache
TemplateCache.clear("#my-template", "#this-template");
```

## Customizing Template Access

If you want to use an alternate template engine while still taking advantage of
the template caching functionality, or want to customize how templates are
stored and retrieved, you will need to customize the `TemplateCache object`. The
default operation of `TemplateCache`, is to retrieve templates from the DOM
based on the containing element's id attribute, and compile the html in that
element with the [underscore.js `template`](http://underscorejs.org#template)
function.

### Override Template Retrieval

The default template retrieval is to select the template contents from the DOM
using jQuery. If you wish to change the way this works, you can override the
`loadTemplate` method on the `TemplateCache` object.

```javascript
var TemplateCache = require('marionette.templatecache');

var myTemplateFunc = function(selector) {
  // custom template logic
};

TemplateCache.prototype.loadTemplate = function(templateId, options){
  // load your template here, returning the data needed for the compileTemplate
  // function. For example, you have a function that creates templates based on the
  // value of templateId
  var myTemplate = myTemplateFunc(templateId);

  // send the template back
  return myTemplate;
};
```

### Override Template Compilation

The default template compilation passes the results from `loadTemplate` to the
`compileTemplate` function, which returns an underscore.js compiled template
function. When overriding `compileTemplate` remember that it must return a
function which takes an object of parameters and values and returns a formatted
HTML string.

```javascript
var Handlebars = require('handlebars');
var TemplateCache = require('marionette.templatecache');

TemplateCache.prototype.compileTemplate = function(rawTemplate, options) {
  // use Handlebars.js to compile the template
  return Handlebars.compile(rawTemplate);
};
```