silverstripe-framework/docs/en/02_Developer_Guides/01_Templates/05_Template_Inheritance.md

title: Template Inheritance summary: Override and extend module and core markup templates from your application code.

Template Inheritance

Bundled within SilverStripe are default templates for any markup the framework outputs for things like Form templates, Emails or RSS Feeds. These templates are provided to make getting your site up and running quick with sensible defaults but it's easy to replace and customise SilverStripe (and add-on's) by providing custom templates in your own mysite/templates folder or in your themes/your_theme/templates folder.

Take for instance the GenericEmail template in SilverStripe. This is the HTML default template that any email created in SilverStripe is rendered with. It's bundled in the core framework at framework/templates/email/GenericEmail.ss.

Instead of editing that file to provide a custom template for your application, simply define a template of the same name in the mysite/templates/email folder or in the themes/your_theme/templates/email folder if you're using themes.

mysite/templates/email/GenericEmail.ss

	$Body

	<p>Thanks from Bob's Fantasy Football League.</p>

All emails going out of our application will have the footer Thanks from Bob's Fantasy Football Leaguee added.

As we've added a new file, make sure you flush your SilverStripe cache by visiting `http://yoursite.com/?flush=1`

Template inheritance works on more than email templates. All files within the templates directory including includes, layout or anything else from core (or add-on's) template directory can be overridden by being located inside your mysite/templates directory. SilverStripe keeps an eye on what templates have been overridden and the location of the correct template through a ThemeResourceLoader.

ThemeResourceLoader

The location of each template and the hierarchy of what template to use is stored within a ThemeResourceLoader instance. This is a serialized object containing a map of ThemeManifest instances. For SilverStripe to find the GenericEmail template it does not check all your template folders on the fly, it simply asks the manifests. The manifests are created and added to the loader when the kernel is instantiated.

Template Priority

The order in which templates are selected from themes can be explicitly declared through configuration. To specify the order you want, make a list of the module names under SilverStripe\Core\Manifest\ModuleManifest.module_priority in a configuration YAML file.

some-module/_config.yml

SilverStripe\Core\Manifest\ModuleManifest:
  module_priority:
    - 'example/module-one'
    - 'example/module-two'
    - '$other_modules'
    - 'example/module-three'

The placeholder $other_modules is used to mark where all of the modules not specified in the list should appear. (In alphabetical order of their containing directory names).

In this example, the module named example/module-one has the highest level of precedence, followed by example/module-two. The module example/module-three is guaranteed the lowest level of precedence.

Defining a "project"

It is a good idea to define one of your modules as the project. Commonly, this is the mysite/ module, but there is nothing compulsory about that module name. The "project" module can be specified as a variable in the module_priorities list, as well.

some-module/_config.yml

SilverStripe\Core\Manifest\ModuleManifest:
  project: 'myapp'
  module_priority:
    - '$project'
    - '$other_modules'

About module "names"

Module names are derived their local composer.json files using the following precedence:

• The value of the name attribute in composer.json
• The value of extras.installer_name in composer.json
• The basename of the directory that contains the module

Nested Layouts through $Layout

SilverStripe has basic support for nested layouts through a fixed template variable named $Layout. It's used for storing top level template information separate to individual page layouts.

When $Layout is found within a root template file (one in templates), SilverStripe will attempt to fetch a child template from the templates/Layout directory. It will do a full sweep of your modules, core and custom code as it would if it was looking for a new root template.

This is better illustrated with an example. Take for instance our website that has two page types Page and HomePage.

Our site looks mostly the same across both templates with just the main content in the middle changing. The header, footer and navigation will remain the same and we don't want to replicate this work across more than one spot. The $Layout function allows us to define the child template area which can be overridden.

mysite/templates/Page.ss

    <html>
    <head>
        ..
    </head>
    
    <body>
        <% include Header %>
        <% include Navigation %>

        $Layout

        <% include Footer %>
    </body>
``
**mysite/templates/Layout/Page.ss**
```ss
	<p>You are on a $Title page</p>

	$Content

mysite/templates/Layout/HomePage.ss

	<h1>This is the homepage!</h1>

	<blink>Hi!</blink>

If your classes have in a namespace, the Layout folder will be a found inside of the appropriate namespace folder.

For example, the layout template for SilverStripe\Control\Controller will be found at templates/SilverStripe/Control/Layout/Controller.ss.