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Requirements

The requirements class takes care of including CSS and JavaScript into your applications. This is preferred to hard coding any references in the <head> tag of your template, as it enables a more flexible handling through the Requirements class.

Template Requirements API

mysite/templates/Page.ss

<% require css("cms/css/TreeSelector.css") %>
<% require themedCSS("TreeSelector") %>
<% require javascript("cms/javascript/LeftAndMain.js") %>

Requiring assets from the template is restricted compared to the PHP API.

PHP Requirements API

It is common practice to include most Requirements either in the init()-method of your controller, or as close to rendering as possible (e.g. in FormField.

<?php

class MyCustomController extends Controller {

    public function init() {
        parent::init();

        Requirements::javascript("cms/javascript/LeftAndMain.js");
        Requirements::css("cms/css/TreeSelector.css");
    }
}

CSS Files

Requirements::css($path, $media);

If you're using the CSS method a second argument can be used. This argument defines the 'media' attribute of the <link> element, so you can define 'screen' or 'print' for example.

Requirements::css("cms/css/TreeSelector.css", "screen,projection");

Javascript Files

Requirements::javascript($path);

A variant on the inclusion of custom javascript is the inclusion of templated javascript. Here, you keep your JavaScript in a separate file and instead load, via search and replace, several PHP-generated variables into that code.

$vars = array(
    "EditorCSS" => "cms/css/editor.css",
);

Requirements::javascriptTemplate("cms/javascript/editor.template.js", $vars);

In this example, editor.template.js is expected to contain a replaceable variable expressed as $EditorCSS.

Custom Inline CSS or Javascript

You can also quote custom script directly. This may seem a bit ugly, but is useful when you need to transfer some kind of 'configuration' from the database in a raw format. You'll need to use the heredoc syntax to quote JS and CSS, this is generally speaking the best way to do these things - it clearly marks the copy as belonging to a different language.

Requirements::customScript(<<<JS
  alert("hi there");
JS
);

Requirements::customCSS(<<<CSS
  .tree li.$className {
    background-image: url($icon);
  }
CSS
);

Combining Files

You can concatenate several CSS or javascript files into a single dynamically generated file. This increases performance by reducing HTTP requests.

Requirements::combine_files(
    'foobar.js',
    array(
        'mysite/javascript/foo.js',
        'mysite/javascript/bar.js',
    )
);

To make debugging easier in your local environment, combined files is disabled when running your application in dev mode.

By default it stores the generated file in the assets/ folder, but you can configure this by pointing the Requirements.combined_files_folder configuration setting to a specific folder.

mysite/_config/app.yml

Requirements:
  combined_files_folder: '_combined'

If SilverStripe doesn't have permissions on your server to write these files it will default back to including them individually. SilverStripe will not rewrite your paths within the file.

You can also combine CSS files into a media-specific stylesheets as you would with the Requirements::css call - use the third paramter of the combine_files function:

$printStylesheets = array(
    "$themeDir/css/print_HomePage.css",
    "$themeDir/css/print_Page.css",
);

Requirements::combine_files('print.css', $printStylesheets, 'print');

Clearing assets

Requirements::clear();

Clears all defined requirements. You can also clear specific requirements.

Requirements::clear(THIRDPARTY_DIR.'/prototype.js');

Depending on where you call this command, a Requirement might be re-included afterwards.

Blocking

Requirements can also be explicitly blocked from inclusion, which is useful to avoid conflicting JavaScript logic or CSS rules. These blocking rules are independent of where the block() call is made. It applies both for already included requirements, and ones included after the block() call.

One common example is to block the core jquery.js added by various form fields and core controllers, and use a newer version in a custom location. This assumes you have tested your application with the newer version.

Requirements::block(THIRDPARTY_DIR . '/jquery/jquery.js');

The CMS also uses the Requirements system, and its operation can be affected by block() calls. Avoid this by limiting the scope of your blocking operations, e.g. in init() of your controller.

Inclusion Order

Requirements acts like a stack, where everything is rendered sequentially in the order it was included. There is no way to change inclusion-order, other than using Requirements::clear and rebuilding the whole set of requirements.

Inclusion order is both relevant for CSS and Javascript files in terms of dependencies, inheritance and overlays - be careful when messing with the order of requirements.

Javascript placement

By default, SilverStripe includes all Javascript files at the bottom of the page body, unless there's another script already loaded, then, it's inserted before the first <script> tag. If this causes problems, it can be configured.

mysite/_config/app.yml

Requirements:
  write_js_to_body: true
  force_js_to_bottom: true

Requirements.force_js_to_bottom, will force SilverStripe to write the Javascript to the bottom of the page body, even if there is an earlier script tag.

API Documentation