silverstripe-framework/docs/en/tutorials/2-extending-a-basic-site.md

Tutorial 2 - Extending a basic site

Overview

In the first tutorial we learnt how to create a basic site using SilverStripe. This tutorial will build on that, and explore extending SilverStripe by creating our own page types. After doing this we should have a better understanding of how SilverStripe works.

What are we working towards?

We are going to work on adding two new sections to the site we built in the first tutorial.

The first of these new sections will be News, with a recent news listing on the homepage and an RSS feed:

The second will be a Staff section, to demonstrate more complex database structures (such as associating an image with each staff member):

The SilverStripe data model

A large part of designing complex SilverStripe sites is the creation of our own page types. Before we progress any further, it is important to understand what a page type is and how the SilverStripe data model works.

SilverStripe is based on the "Model-View-Controller" design pattern. This means that SilverStripe attempts to separate data, logic and presentation as much as possible. Every page has three separate parts which are combined to give you the final page. Lets look at each one individually:

Model

All content on our site is stored in a database. Each class that is a child of the [api:DataObject] class will have its own table in our database.

Every object of such a class will correspond to a row in that table - this is our "data object", the "model" of Model-View-Controller. A page type has a data object that represents all the data for our page. Rather than inheriting directly from [api:DataObject], it inherits from [api:SiteTree]. We generally create a "Page" data object, and subclass this for all other page types. This allows us to define behavior that is consistent across all pages in our site.

View

The "view" is the presentation of our site. As we have already seen, the templates SilverStripe uses to render a page are dependent on the page type. Using templates and css, we are able to have full control over the presentation of our website.

Controller

Each page type also has a "controller". The controller contains all the code used to manipulate our data before it is rendered. For example, suppose we were making an auction site, and we only wanted to display the auctions closing in the next ten minutes. We would implement this logic in the controller. The controller for a page should inherit from [api:ContentController]. Just as we create a "Page" data object and subclass it for the rest of the site, we also create a "Page_Controller" that is subclassed.

Creating a new page type requires creating each of these three elements. We will then have full control over presentation, the database, and editable CMS fields.

A more in-depth introduction of Model-View-Controller can be found here.

Creating the news section page types

To create a news section we'll need two new page types. The first one is obvious: we need an ArticlePage page type. The second is a little less obvious: we need an ArticleHolder page type to contain our article pages.

We'll start with the ArticlePage page type. First we create the model, a class called "ArticlePage". We put the ArticlePage class into a file called "ArticlePage.php" inside mysite/code. All other classes relating to ArticlePage should be placed within "ArticlePage.php", this includes our controller (ArticlePage_Controller).

mysite/code/ArticlePage.php

:::php
<?php
class ArticlePage extends Page {
}
class ArticlePage_Controller extends Page_Controller {
}

Here we've created our data object/controller pair, but we haven't extended them at all. Don't worry about the $db and $has_one arrays just yet, we'll explain them shortly. SilverStripe will use the template for the Page page type as explained in the first tutorial, so we don't need to specifically create the view for this page type.

Let's create the ArticleHolder page type.

mysite/code/ArticleHolder.php

:::php
<?php
class ArticleHolder extends Page {
	private static $allowed_children = array('ArticlePage');
}
class ArticleHolder_Controller extends Page_Controller {
}

Here we have done something interesting: the $allowed_children field. This is one of a number of static fields we can define to change the properties of a page type. The $allowed_children field is an array of page types that are allowed to be children of the page in the site tree. As we only want news articles in the news section, we only want pages of the type ArticlePage as children. We can enforce this in the CMS by setting the $allowed_children field within this class.

We will be introduced to other fields like this as we progress; there is a full list in the documentation for [api:SiteTree].

Now that we have created our page types, we need to let SilverStripe rebuild the database: http://localhost/your_site_name/dev/build. SilverStripe should detect that there are two new page types, and add them to the list of page types in the database.

It is SilverStripe convention to suffix general page types with "Page", and page types that hold other page types with "Holder". This is to ensure that we don't have URLs with the same name as a page type; if we named our *ArticleHolder* page type "News", it would conflict with the page name also called "News".

Adding date and author fields

Now that we have an ArticlePage page type, let's make it a little more useful. Remember the $db array? We can use this array to add extra fields to the database. It would be nice to know when each article was posted, and who posted it. Add a $db property definition in the ArticlePage class:

:::php
<?php
class ArticlePage extends Page {
	private static $db = array(
		'Date' => 'Date',
		'Author' => 'Text'
	);

	// .....
}

Every entry in the array is a key => value pair. The key is the name of the field, and the value is the type. See "data types" for a complete list of types.

The names chosen for the fields you add must not already be used. Be careful using field names such as Title, Content etc. as these may already be defined in the page types your new page is extending from.

When we rebuild the database, we will see that the ArticlePage table has been created. Even though we had an ArticlePage page type before, a table was not created because there were no fields unique to the article page type. There are now extra fields in the database, but still no way of changing them.

To add our new fields to the CMS we have to override the getCMSFields() method, which is called by the CMS when it creates the form to edit a page. Add the method to the ArticlePage class.

:::php
<?php
class ArticlePage extends Page {
	// ...
	
	public function getCMSFields() {
		$fields = parent::getCMSFields();
		
		$dateField = new DateField('Date');
		$dateField->setConfig('showcalendar', true);
		$fields->addFieldToTab('Root.Main', $dateField, 'Content');
		$fields->addFieldToTab('Root.Main', new TextField('Author'), 'Content');
		
		return $fields;
	}
}

// ...

Let's walk through this method.

:::php
$fields = parent::getCMSFields();

Firstly, we get the fields from the parent class; we want to add fields, not replace them. The $fields variable returned is a [api:FieldList] object.

:::php
$fields->addFieldToTab('Root.Main', new TextField('Author'), 'Content');
$fields->addFieldToTab('Root.Main', new DateField('Date'), 'Content');

We can then add our new fields with addFieldToTab. The first argument is the tab on which we want to add the field to: "Root.Main" is the tab which the content editor is on. The second argument is the field to add; this is not a database field, but a [api:FormField] - see the documentation for more details.

Note: By default, the CMS only has one tab. Creating new tabs is much like adding to existing tabs. For instance: `$fields->addFieldToTab('Root.NewTab', new TextField('Author'));` would create a new tab called "New Tab", and a single "Author" textfield inside.

We have added two fields: A simple [api:TextField] and a [api:DateField].
There are many more fields available in the default installation, listed in "form field types".

:::php
return $fields;

Finally, we return the fields to the CMS. If we flush the cache (by adding ?flush=1 at the end of the URL), we will be able to edit the fields in the CMS.

Now that we have created our page types, let's add some content. Go into the CMS and create an ArticleHolder page named "News", then create a few ArticlePage's within it.

Modifing the date field

At the moment, your date field will look just like a text field. This makes it confusing and doesn't give the user much help when adding a date.

To make the date field a bit more user friendly, you can add a dropdown calendar, set the date format and add better title. By default, the date field will have the date format defined by your locale.

:::php
<?php
class ArticlePage extends Page {

// .....

public function getCMSFields() {
	$fields = parent::getCMSFields();
	
	$fields->addFieldToTab('Root.Main', $dateField = new DateField('Date','Article Date (for example: 20/12/2010)'), 'Content');
	$dateField->setConfig('showcalendar', true);
	$fields->addFieldToTab('Root.Main', $dateField, 'Content');
	$fields->addFieldToTab('Root.Main', new TextField('Author'), 'Content');

	return $fields;
}

Let's walk through these changes.

:::php
$fields->addFieldToTab('Root.Main', $dateField = new DateField('Date','Article Date (for example: 20/12/2010)'), 'Content');

$dateField is declared only to in order to change the configuration of the DateField.

:::php
$dateField->setConfig('showcalendar', true);

By enabling showCalendar you show a calendar overlay when clicking on the field.

:::php
$dateField->setConfig('dateformat', 'dd/MM/YYYY');

dateFormat allows you to specify how you wish the date to be entered and displayed in the CMS field. See the [api:DateField] documentation for more configuration options.

:::php
$fields->addFieldToTab('Root.Main', new TextField('Author','Author Name'), 'Content');

By default the field name 'Date' or 'Author' is shown as the title, however this might not be that helpful so to change the title, add the new title as the second argument.

Creating the templates

Because our new pages inherit their templates from Page, we can view anything entered in the content area when navigating to these pages on our site. However, as there is no reference to the date or author fields in the Page template this data is not being displayed.

To fix this we will create a template for each of our new page types. We'll put these in themes/simple/templates/Layout so we only have to define the page specific parts: SilverStripe will use themes/simple/templates/Page.ss for the basic page layout.

ArticlePage Template

First, the template for displaying a single article:

themes/simple/templates/Layout/ArticlePage.ss

:::ss
<% include SideBar %>
<div class="content-container unit size3of4 lastUnit">
	<article>
		<h1>$Title</h1>
		<div class="news-details">
			<p>Posted on $Date.Nice by $Author</p>
		</div>
		<div class="content">$Content</div>
	</article>
		$Form
</div>

Most of the code is just like the regular Page.ss, we include an informational div with the date and the author of the Article.

To access the new fields, we use $Date and $Author. In fact, all template variables and page controls come from either the data object or the controller for the page being displayed. The $Title variable comes from the Title field of the [api:SiteTree] class. $Date and $Author come from the ArticlePage table through your custom Page. $Content comes from the SiteTree table through the same data object. The data for your page is spread across several tables in the database matched by id - e.g. Content is in the SiteTree table, and Date and Author are in the ArticlePage table. SilverStripe matches this data, and collates it into a single data object.

Rather than using $Date directly, we use $Date.Nice. If we look in the [api:Date] documentation, we can see that the Nice function returns the date in dd/mm/yyyy format, rather than the yyyy-mm-dd format stored in the database.

###ArticleHolder Template We'll now create a template for the article holder. We want our news section to show a list of news items, each with a summary and a link to the main article (our Article Page).

themes/simple/templates/Layout/ArticleHolder.ss

:::ss
<% include SideBar %>
<div class="content-container unit size3of4 lastUnit">  
	<article>
		<h1>$Title</h1>
		$Content        
		<div class="content">$Content</div>
	</article>
	<% loop $Children %>
		<article>
			<h2><a href="$Link" title="Read more on &quot;{$Title}&quot;">$Title</a></h2>
			<p>$Content.FirstParagraph</p>
			<a href="$Link" title="Read more on &quot;{$Title}&quot;">Read more &gt;&gt;</a>
		</article>
	<% end_loop %>
		$Form
</div>

Here we use the page control Children. As the name suggests, this control allows you to iterate over the children of a page. In this case, the children are our news articles. The $Link variable will give the address of the article which we can use to create a link, and the FirstParagraph function of the [api:HTMLText] field gives us a nice summary of the article. The function strips all tags from the paragraph extracted.

Using include files in templates

We can make our templates more modular and easier to maintain by separating commonly-used components in to include files. We are already familiar with the <% include Sidebar %> line from looking at the menu in the first tutorial.

We'll separate the display of linked articles as we want to reuse this code later on.

Cut the code between "loop Children" in ArticleHolder.ss* and replace it with an include statement:

themes/simple/templates/Layout/ArticleHolder.ss

:::ss
...
<% loop $Children %>
	<% include ArticleTeaser %>
<% end_loop %>
...

Paste the code that was in ArticleHolder into a new include file called ArticleTeaser.ss:

themes/simple/templates/Includes/ArticleTeaser.ss

:::ss
<article>
	<h2><a href="$Link" title="Read more on &quot;{$Title}&quot;">$Title</a></h2>
	<p>$Content.FirstParagraph</p>
	<a href="$Link" title="Read more on &quot;{$Title}&quot;">Read more &gt;&gt;</a>
</article>

Changing the icons of pages in the CMS

Let's now make a purely cosmetic change that nevertheless helps to make the information presented in the CMS clearer. Add the following field to the ArticleHolder and ArticlePage classes:

:::php
private static $icon = "framework/docs/en/tutorials/_images/treeicons/news-file.gif";

And this one to the HomePage class:

:::php
private static $icon = "framework/docs/en/tutorials/_images/treeicons/home-file.gif";

This will change the icons for the pages in the CMS.

Showing the latest news on the homepage

It would be nice to greet page visitors with a summary of the latest news when they visit the homepage. This requires a little more code though - the news articles are not direct children of the homepage, so we can't use the Children control. We can get the data for news articles by implementing our own function in HomePage_Controller.

mysite/code/HomePage.php

:::php
// ...
public function LatestNews($num=5) {
	$holder = ArticleHolder::get()->First();
	return ($holder) ? ArticlePage::get()->filter('ParentID', $holder->ID)->sort('Date DESC')->limit($num) : false;
}

This function simply runs a database query that gets the latest news articles from the database. By default, this is five, but you can change it by passing a number to the function. See the Data Model documentation for details. We can reference this function as a page control in our HomePage template:

themes/simple/templates/Layout/Homepage.ss

:::ss
<!-- ... -->
<div class="content">$Content</div>
</article>
<% loop $LatestNews %>
	<% include ArticleTeaser %>
<% end_loop %>

When SilverStripe comes across a variable or page control it doesn't recognize, it first passes control to the controller. If the controller doesn't have a function for the variable or page control, it then passes control to the data object. If it has no matching functions, it then searches its database fields. Failing that it will return nothing.

The controller for a page is only created when page is actually visited, while the data object is available when the page is referenced in other pages, e.g. by page controls. A good rule of thumb is to put all functions specific to the page currently being viewed in the controller; only if a function needs to be used in another page should you put it in the data object.

Creating a RSS feed

An RSS feed is something that no news section should be without. SilverStripe makes it easy to create RSS feeds by providing an [api:RSSFeed] class to do all the hard work for us. Create the following function in the ArticleHolder_Controller:

:::php
public function rss() {
	$rss = new RSSFeed($this->Children(), $this->Link(), "The coolest news around");
	return $rss->outputToBrowser();
}

This function creates an RSS feed of all the news articles, and outputs it to the browser. If we go to http://localhost/your_site_name/news/rss we should see our RSS feed. When there is more to a URL after a page's base URL, "rss" in this case, SilverStripe will call the function with that name on the controller if it exists.

Depending on your browser, you should see something like the picture below. If your browser doesn't support RSS, you will most likely see the XML output instead. For more on RSS, see [api:RSSFeed]

Now all we need is to let the user know that our RSS feed exists. Add this function to ArticleHolder_Controller:

:::php
public function init() {
	RSSFeed::linkToFeed($this->Link() . "rss");	
	parent::init();
}

This automatically generates a link-tag in the header of our template. The init function is then called on the parent class to ensure any initialization the parent would have done if we hadn't overridden the init function is still called. Depending on your browser, you can see the RSS feed link in the address bar.

Adding a staff section

Now that we have a complete news section, let's take a look at the staff section. We need to create StaffHolder and StaffPage page types, for an overview on all staff members and a detail-view for a single member. First let's start with the StaffHolder page type.

mysite/code/StaffHolder.php

:::php
<?php

class StaffHolder extends Page {
	private static $db = array();
	private static $has_one = array();
	private static $allowed_children = array('StaffPage');
}

class StaffHolder_Controller extends Page_Controller {
	
}

Nothing here should be new. The StaffPage page type is more interesting though. Each staff member has a portrait image. We want to make a permanent connection between this image and the specific StaffPage (otherwise we could simply insert an image in the $Content field).

mysite/code/StaffPage.php

:::php
<?php
class StaffPage extends Page {
	private static $db = array(
	);
	private static $has_one = array(
		'Photo' => 'Image'
	);
	
	public function getCMSFields() {
		$fields = parent::getCMSFields();
		
		$fields->addFieldToTab("Root.Images", new UploadField('Photo'));
		
		return $fields;
	}
}

class StaffPage_Controller extends Page_Controller {
}

Instead of adding our Image as a field in $db, we have used the $has_one array. This is because an Image is not a simple database field like all the fields we have seen so far, but has its own database table. By using the $has_one array, we create a relationship between the StaffPage table and the Image table by storing the id of the respective Image in the StaffPage table.

We then add an [api:UploadField] in the getCMSFields function to the tab "Root.Images". Since this tab doesn't exist, the addFieldToTab function will create it for us. The UploadField allows us to select an image or upload a new one in the CMS.

Rebuild the database (http://localhost/your_site_name/dev/build) and open the CMS. Create a new StaffHolder called "Staff", and create some StaffPages in it.

Creating the staff section templates

The staff section templates aren't too difficult to create, thanks to the utility methods provided by the [api:Image] class.

themes/simple/templates/Layout/StaffHolder.ss

:::ss
<% include SideBar %>
<div class="content-container unit size3of4 lastUnit">
	<article>
		<h1>$Title</h1>
		$Content        
		<div class="content">$Content</div>
	</article>
	<% loop $Children %>
		<article>
			<h2><a href="$Link" title="Read more on &quot;{$Title}&quot;">$Title</a></h2>
			$Photo.SetWidth(150)
			<p>$Content.FirstParagraph</p>
			<a href="$Link" title="Read more on &quot;{$Title}&quot;">Read more &gt;&gt;</a>
		</article>
	<% end_loop %>
		$Form
</div>

This template is very similar to the ArticleHolder template. The SetWidth method of the [api:Image] class will resize the image before sending it to the browser. The resized image is cached, so the server doesn't have to resize the image every time the page is viewed.

The StaffPage template is also very straight forward.

themes/simple/templates/Layout/StaffPage.ss

:::ss
<% include SideBar %>
<div class="content-container unit size3of4 lastUnit">
	<article>
		<h1>$Title</h1>
		<div class="content">
			$Photo.SetWidth(433)
			$Content</div>
	</article>
		$Form
</div>

Here we use the SetWidth method to get a different sized image from the same source image. You should now have a complete staff section.

Summary

In this tutorial we have explored the concept of page types. In the process of creating and extending page types we have covered many of the concepts required to build a site with SilverStripe.

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