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Aaron Carlino bfc373cf0f update docs with new api

2017-05-25 16:34:32 +12:00

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How to extend the CMS interface

Introduction

The CMS interface works just like any other part of your website: It consists of PHP controllers, templates, CSS stylesheets and JavaScript. Because it uses the same base elements, it is relatively easy to extend.

As an example, we're going to add a permanent "bookmarks" link list to popular pages into the main CMS menu. A page can be bookmarked by a CMS author through a simple checkbox.

For a deeper introduction to the inner workings of the CMS, please refer to our guide on CMS Architecture.

Redux Devtools

It's important to be able to view the state of the React application when you're debugging and building the interface.

To be able to view the state, you'll need to be in a dev environment and have the Redux Devtools installed on Google Chrome or Firefox, which can be found by searching with your favourite search engine.

Overload a CMS template

If you place a template with an identical name into your application template directory (usually mysite/templates/), it'll take priority over the built-in one.

CMS templates are inherited based on their controllers, similar to subclasses of the common Page object (a new PHP class MyPage will look for a MyPage.ss template). We can use this to create a different base template with LeftAndMain.ss (which corresponds to the LeftAndMain PHP controller class).

Copy the template markup of the base implementation at framework/admin/templates/Includes/LeftAndMain_Menu.ss into mysite/templates/Includes/LeftAndMain_Menu.ss. It will automatically be picked up by the CMS logic. Add a new section into the <ul class="cms-menu-list">

:::ss
...
<ul class="cms-menu-list">
	<!-- ... -->
	<li class="bookmarked-link first">
		<a href="{$AdminURL}pages/edit/show/1">Edit "My popular page"</a>
	</li>
	<li class="bookmarked-link last">
		<a href="{$AdminURL}pages/edit/show/99">Edit "My other page"</a>
	</li>
</ul>
...

Refresh the CMS interface with admin/?flush=all, and you should see those hardcoded links underneath the left-hand menu. We'll make these dynamic further down.

Include custom CSS in the CMS

In order to show the links a bit separated from the other menu entries, we'll add some CSS, and get it to load with the CMS interface. Paste the following content into a new file called mysite/css/BookmarkedPages.css:

:::css
.bookmarked-link.first {margin-top: 1em;}

Load the new CSS file into the CMS, by setting the LeftAndMain.extra_requirements_css configuration value.

:::yml
LeftAndMain:
  extra_requirements_css:
    - mysite/css/BookmarkedPages.css

Create a "bookmark" flag on pages

Now we'll define which pages are actually bookmarked, a flag that is stored in the database. For this we need to decorate the page record with a DataExtension. Create a new file called mysite/code/BookmarkedPageExtension.php and insert the following code.

:::php
<?php

class BookmarkedPageExtension extends DataExtension {

	private static $db = array(
		'IsBookmarked' => 'Boolean'
	);

	public function updateCMSFields(FieldList $fields) {
		$fields->addFieldToTab('Root.Main',
			new CheckboxField('IsBookmarked', "Show in CMS bookmarks?")
		);
	}
}

Enable the extension in your configuration file

:::yml
SiteTree:
  extensions:
    - BookmarkedPageExtension

In order to add the field to the database, run a dev/build/?flush=all. Refresh the CMS, open a page for editing and you should see the new checkbox.

Retrieve the list of bookmarks from the database

One piece in the puzzle is still missing: How do we get the list of bookmarked pages from the database into the template we've already created (with hardcoded links)? Again, we extend a core class: The main CMS controller called LeftAndMain.

Add the following code to a new file mysite/code/BookmarkedLeftAndMainExtension.php;

:::php
<?php

class BookmarkedPagesLeftAndMainExtension extends LeftAndMainExtension {

	public function BookmarkedPages() {
		return Page::get()->filter("IsBookmarked", 1);
	}
}

Enable the extension in your configuration file

:::yml
LeftAndMain:
  extensions:
    - BookmarkedPagesLeftAndMainExtension

As the last step, replace the hardcoded links with our list from the database. Find the <ul> you created earlier in mysite/admin/templates/LeftAndMain.ss and replace it with the following:

:::ss
<ul class="cms-menu-list">
	<!-- ... -->
	<% loop $BookmarkedPages %>
	<li class="bookmarked-link $FirstLast">
		<li><a href="{$AdminURL}pages/edit/show/$ID">Edit "$Title"</a></li>
	</li>
	<% end_loop %>
</ul>

Extending the CMS actions

CMS actions follow a principle similar to the CMS fields: they are built in the backend with the help of FormFields and FormActions, and the frontend is responsible for applying a consistent styling.

The following conventions apply:

New actions can be added by redefining getCMSActions, or adding an extension with updateCMSActions.
It is required the actions are contained in a FieldSet (getCMSActions returns this already).
Standalone buttons are created by adding a top-level FormAction (no such button is added by default).
Button groups are created by adding a top-level CompositeField with FormActions in it.
A MajorActions button group is already provided as a default.
Drop ups with additional actions that appear as links are created via a TabSet and Tabs with FormActions inside.
A ActionMenus.MoreOptions tab is already provided as a default and contains some minor actions.
You can override the actions completely by providing your own getAllCMSFields.

Let's walk through a couple of examples of adding new CMS actions in getCMSActions.

First of all we can add a regular standalone button anywhere in the set. Here we are inserting it in the front of all other actions. We could also add a button group (CompositeField) in a similar fashion.

:::php
$fields->unshift(FormAction::create('normal', 'Normal button'));

We can affect the existing button group by manipulating the CompositeField already present in the FieldList.

:::php
$fields->fieldByName('MajorActions')->push(FormAction::create('grouped', 'New group button'));

Another option is adding actions into the drop-up - best place for placing infrequently used minor actions.

:::php
$fields->addFieldToTab('ActionMenus.MoreOptions', FormAction::create('minor', 'Minor action'));

We can also easily create new drop-up menus by defining new tabs within the TabSet.

:::php
$fields->addFieldToTab('ActionMenus.MyDropUp', FormAction::create('minor', 'Minor action in a new drop-up'));

Empty tabs will be automatically removed from the `FieldList` to prevent clutter.

To make the actions more user-friendly you can also use alternating buttons as detailed in the CMS Alternating Button how-to.

React components

Some admin modules render their UI with React, a popular Javascript library created by Facebook. For these sections, rendering happens via client side scripts that create and inject HTML declaratively using data structures. These UI elements are known as "components" and represent the fundamental building block of a React-rendered interface.

For example, a component expressed like this:

<PhotoItem size={200} caption={'Angkor Wat'} onSelect={openLightbox}>
	<img src="path/to/image.jpg" />
</PhotoItem>

Might actually render HTML that looks like this:

<div class="photo-item">
	<div class="photo" style="width:200px;height:200px;">
		<img src="path/to/image.jpg">
	</div>
	<div class="photo-caption">
		<h3><a>Angkor Wat/a></h3>
	</div> 
</div>

This syntax is known as JSX. It is transpiled at build time into native Javascript calls to the React API. While optional, it is recommended to express components this way.

This documentation will stop short of explaining React in-depth, as there is much better documentation available all over the web. We recommend:

A few words about ES6

The remainder of this tutorial is written in ECMAScript 6, or ES6 for short. This is the new spec for Javascript (currently ES5) that is as of this writing only partially implmented in modern browsers. Because it doesn't yet enjoy vast native support, it has to be transpiled in order to work in a browser. This transpiling can be done using a variety of toolchains, but the basic principle is that a browser-ready, ES5 version of your code is generated in your dev environment as part of your workflow.

As stated above, there are many ways to solve the problem of transpiling. The toolchain we use in core SilverStripe modules includes:

Babel (ES6 transpiler)
Webpack (Module bundler)

Using dependencies within your component

If your component has dependencies, you can add them via the injector using the inject() higher order component. The function accepts the following arguments:

inject(Component, [dependencies], mapDependenciesToProps)

Component The component definition to inject into
[dependencies]: An array of dependencies (or a string, if just one)
mapDependenciesToProps: (optional) All depdencies are passed into this function as params. The function is expected to return a map of props to dependencies. If this parameter is not specified, the prop names and the service names will mirror each other.

my-module/js/components/Gallery.js

import React from 'react';
import { inject } from 'lib/Injector';

class Gallery extends React.Component {
  render() {
    const { SearchComponent, ItemComponent } = this.props;
    return (
      <div>  
         <SearchComponent />
        {this.props.items.map(item => (
          <ItemComponent title={item.title} image={item.image} />
        ))}
      </div>
    );
  }
}

export default inject(
  Gallery, 
  ['GalleryItem', 'SearchBar'], 
  (GalleryItem, SearchBar) => ({
    ItemComponent: GalleryItem,
    SearchComponent: SearchBar
  })
 );

Customising React components

React components can be customised in a similar way to PHP classes, using a dependency injection API. The key difference is that components are not overriden the way backend services are. Rather, new components are composed using higher order components. This has the inherent advantage of allowing all thidparty code to have an influence over the behaviour, state, and UI of a component.

A simple higher order component

Using our example above, let's create a customised PhotoItem that allows a badge, perhaps indicating that it is new to the gallery.

const enhancedPhoto = (PhotoItem) => (props) => {
	const badge = props.isNew ? 
	  <div className="badge">New!</div> : 
	  null;

	return (
		<div>
			{badge}
			<PhotoItem {...props} />
		</div>
	);
}

const EnhancedPhotoItem = enhancedPhoto(PhotoItem);

<EnhancedPhotoItem isNew={true} size={300} />

Alternatively, this component could be expressed with an ES6 class, rather than a simple function.

const enhancedPhoto = (PhotoItem) => {
	return class EnhancedPhotoItem extends React.Component {
		render() {
			const badge = this.props.isNew ? 
			  <div className="badge">New!</div> : 
			  null;

			return (
				<div>
					{badge}
					<PhotoItem {...this.props} />
				</div>
			);

		}
	}
}

When components are stateless, using a simple function in lieu of a class is recommended.

Using the injector to customise a core component

Let's make a more awesome text field. Because the TextField component is fetched through the injector, we can override it and augment it with our own functionality.

In this example, we'll add a simple character count below the text field.

First, let's create our higher order component. my-module/js/components/CharacterCounter.js

import React from 'react';

const CharacterCounter = (TextField) => (props) => {
    return (
        <div>
            <TextField {...props} />
            <small>Character count: {props.value.length}</small>
        </div>
    );
}

export default CharacterCounter;

Now let's add this higher order component to the injector.

my-module/js/main.js

import Injector from 'lib/Injector';
import CharacterCounter from './components/CharacterCounter';

Injector.transform('my-transformation', (update) => {
  update('TextField', CharacterCounter);
});

Much like the configuration layer, we need to specify a name for this transformation. This will help other modules negotiate their priority over the injector in relation to yours.

The second parameter of the transform argument is a callback which receives a update() function that allows you to mutate the DI container with a wrapper for the component. Remember, this function does not replace the component -- it enhances it with new functionality.

The last thing we'll have to do is transpile our code and load the resulting bundle file into the admin page.

my-module/_config/config.yml

    ---
    Name: my-module
    ---
    SilverStripe\Admin\LeftAndMain:
      extra_requirements_javascript:
        # The name of this file will depend on how you've configured your build process
        - 'my-module/js/dist/main.bundle.js'

Now that the customisation is applied, our text fields look like this:

Let's add another customisation to TextField. If the text goes beyond a specified length, let's throw a warning in the UI.

my-module/js/components/TextLengthChecker.js

const TextLengthCheker = (TextField) => (props) => {  
  const {limit, value } = props;
  const invalid = limit !== undefined && value.length > limit;

  return (
    <div>
      <TextField {...props} />
      {invalid &&
        <span style={{color: 'red'}}>
          {`Text is too long! Must be ${limit} characters`}
        </span>
      }
    </div>
  );
}

export default TextLengthChecker;

We'll apply this one to the injector as well, but let's do it under a different name. For the purposes of demonstration, let's imagine this customisation comes from another module.

my-module/js/main.js

import Injector from 'lib/Injector';
import TextLengthChecker from './components/TextLengthChecker';

Injector.transform('my-other-transformation', (update) => {
  update('TextField', TextLengthChecker);
});

Now, both components have applied themselves to the textfield.

Getting multiple customisations to work together

Both these enhancements are nice, but what would be even better is if they could work together collaboratively so that the character count only appeared when the user input got within a certain range of the limit. In order to do that, we'll need to be sure that the TextLengthChecker customisation is loaded ahead of the CharacterCounter customisation.

First let's update the character counter to show characters remaining, which is much more useful. We'll also update the API to allow a warningBuffer prop. This is the amount of characters the input can be within the limit before the warning shows.

my-module/js/components/CharacterCounter.js

import React from 'react';

const CharacterCounter = (TextField) => (props) => {
    const { warningBuffer, limit, value: { length } } = props;
    const remainingChars = limit - length;
    const showWarning = length + warningBuffer >= limit;
    return (
        <div>
            <TextField {...props} />
            {showWarning &&
            	<small>Characters remaining: {remainingChars}</small>
            }
        </div>
    );
}

export default CharacterCounter;

Now, when we apply this customisation, we need to be sure it loads after the length checker in the middleware chain, as it relies on the prop limit. We can do that by specifying priority using before and after metadata to the customisation.

For this example, we'll imagine these two enhancements come from different modules.

module-a/js/main.js

import Injector from 'lib/Injector';
import CharacterCounter from './components/CharacterCounter';
Injector.transform(
  'my-transformation', 
  (update) => update('TextField', CharacterCounter),
  { after: 'my-other-transformation' }
);

module-b/js/main.js

import Injector from 'lib/Injector';
import TextLengthChecker from './components/TextLengthChecker';

Injector.transform(
  'my-other-transformation', 
  (update) => update('TextField', TextLengthChecker),
  { before: 'my-transformation' }
);

Now, both components, coming from different modules, play together nicely, in the correct order.

before and after also accept arrays of constraints.

Injector.transform(
  'my-transformation', 
  (update) => update('TextField', TextLengthChecker),
  { before: ['my-transformation', 'some-other-transformation'] }
);

Using the * flag

If you really want to be sure your customisation gets loaded first or last, you can use * as your before or after reference.

Injector.transform(
  'my-transformation', 
  (update) => update('TextField', FinalTransform),
  { after: '*' }
);

Note: This flag can only be used once per transformation. The following are not allowed:

{ before: ['*', 'something-else'] }
{ after: '*', before: 'something-else' }

Helpful tip: Name your higher order components

Now that we have multiple enhancements happening to the same component, it will be really useful for debugging purposes to reveal the names of each enhancement on the displayName of the component. This will really help you when viewing the rendered component tree in React Dev Tools.

For this, you can use the third parameter of the update() function. It takes an arbitrary name for the enhancement you're applying.

module-a/js/main.js

(update) => update('TextField', CharacterCounter, 'CharacterCounter')

module-b/js/main.js

(update) => update('TextField', TextLengthChecker, 'TextLengthChecker')

Dealing with events

Let's make a new customisation that customises the behaviour of a button. We'll have all form actions throw a window.confirm() message before executing their action. Further, we'll apply some new style to the button if it is in a loading state.

my-module/js/components/ConfirmingFormButton.js

import React from 'react';

export default (FormAction) => (props) => {
  const newProps = {
    ...props,
    data: {
      ...props.data,
      buttonStyle: props.loading ? 'danger' : props.data.buttonStyle
    },
    handleClick(e) {
      if(window.confirm('Did you really mean to click this?')) {
        props.handleClick(e);
      }
    }
  }

  return <FormAction {...newProps} />
}

my-module/js/main.js

import ConfirmingFormButton from './components/ConfirmingFormButton';

Injector.transform('my-transformation', (update) => {
  update('FormAction', ConfirmingFormButton, 'ConfirmingFormButton');
});

Registering new React components

If you've created a module using React, it's a good idea to afford other developers an API to enhance those components. To do that, simply register them with Injector.

my-public-module/js/main.js

import Injector from 'lib/Injector';

Injector.register('MyComponent', MyComponent);

Now other developers can customise your components with Injector.update().

Note: Overwriting components by calling register() multiple times for the same service name is discouraged, and will throw an error. Should you really need to do this, you can pass { force: true } as the third argument to the register() function.

Using the injector directly within your component

On rare occasions, you may just want direct access to the injector in your component. If your dependency requirements are dynamic, for example, you won't be able to explicitly declare them in inject(). In cases like this, use withInjector(). This higher order component puts the Injector instance in context.

class MyGallery extends React.Component {
  render () {
    <div>
      {this.props.items.map(item => {
        const Component = this.context.injector.get(item.type);
        return <Component title={item.title} image={item.image} />
      })}
    </div>
  }
}

export default withInjector(MyGallery);

Interfacing with legacy CMS JavaScript

One of the great things about ReactJS is that it works great with DOM based libraries like jQuery and Entwine. To allow legacy-land scripts to notify your React component about changes, add the following.

my-component.js

import SilverStripeComponent from 'silverstripe-component';

class MyComponent extends SilverStripeComponent {
	componentDidMount() {
		super.componentDidMount();
	}
	
	componentWillUnmount() {
		super.componentWillUnmount();
	}
}

export default MyComponent;

This is functionally no different from the first example. But it's a good idea to be explicit and add these super calls now. You will inevitably add componentDidMount and componentWillUnmount hooks to your component and it's easy to forget to call super then.

So what's going on when we call those? Glad you asked. If you've passed cmsEvents into your component's props, wonderful things will happen.

Let's take a look at some examples.

Getting data into a component

Sometimes you'll want to call component methods when things change in legacy-land. For example when a CMS tab changes you might want to update some component state.

main.js

import $ from 'jquery';
import React, { PropTypes, Component } from 'react';
import MyComponent from './my-component';

$.entwine('ss', function ($) {
	$('.my-component-wrapper').entwine({
		getProps: function (props) {
			var defaults = {
				cmsEvents: {
					'cms.tabchanged': function (event, title) {
						// Call a Redux action to update state.
					}
				}
			};
			
			return $.extend(true, defaults, props);
		},
		onadd: function () {
			var props = this.getProps();
			
			React.render(
				<MyComponent {...props} />,
				this[0]
			);
		}
	});
});

legacy.js

(function ($) {
	$.entwine('ss', function ($) {
		$('.cms-tab').entwine({
			onclick: function () {
				$(document).trigger('cms.tabchanged', this.find('.title').text());
			}
		});
	});
}(jQuery));

Each key in props.cmsEvents gets turned into an event listener by SilverStripeComponent.componentDidMount. When a legacy-land script triggers that event on document, the associated component callback is invoked, with the component's context bound to it.

All SilverStripeComponent.componentWillUnmount does is clean up the event listeners when they're no longer required.

There are a couple of important things to note here:

Both files are using the same ss namespace.
Default properties are defined using the getProps method.

This gives us the flexibility to add and override event listeners from legacy-land. We're currently updating the current tab's title when .cms-tab is clicked. But say we also wanted to highlight the tab. We could do something like this.

legacy.js

(function ($) {
	$.entwine('ss', function ($) {
		$('.main .my-component-wrapper').entwine({
			getProps: function (props) {
				return this._super({
					cmsEvents: {
						'cms.tabchanged': function (event, title) {
							// Call a Redux action to update state.
						}
					}
				});
			}
		});
		
		$('.cms-tab').entwine({
			onclick: function () {
				$(document).trigger('cms.tabchanged', this.find('.title').text());
			}
		});
	});
}(jQuery));

Here we're using Entwine to override the getProps method in main.js. Note we've made the selector more specific .main .my-component-wrapper. The most specific selector comes first in Entwine, so here our new getProps gets called, which passes the new callback to the getProps method defined in main.js.

Getting data out of a component

There are times you'll want to update things in legacy-land when something changes in you component.

SilverStripeComponent has a handly method emitCmsEvents to help with this.

my-component.js

import SilverStripeComponent from 'silverstripe-component';

class MyComponent extends SilverStripeComponent {
	componentDidMount() {
		super.componentDidMount();
	}
	
	componentWillUnmount() {
		super.componentWillUnmount();
	}
	
	componentDidUpdate() {
		this.emitCmsEvent('my-component.title-changed', this.state.title);
	}
}

export default MyComponent;

legacy.js

(function ($) {
	$.entwine('ss', function ($) {
		$('.cms-tab').entwine({
			onmatch: function () {
				var self = this;

				$(document).on('my-component.title-changed', function (event, title) {
					self.find('.title').text(title);
				});
			},
			onunmatch: function () {
				$(document).off('my-component.title-changed');
			}
		});
	});
}(jQuery));

Implementing handlers

Your newly created buttons need handlers to bind to before they will do anything. To implement these handlers, you will need to create a LeftAndMainExtension and add applicable controller actions to it:

:::php
class CustomActionsExtension extends LeftAndMainExtension {
	
	private static $allowed_actions = array(
    	'sampleAction'
	);
	
	public function sampleAction()
	{
		// Create the web
	}
	
}

The extension then needs to be registered:

:::yaml
LeftAndMain:
	extensions:
		- CustomActionsExtension

You can now use these handlers with your buttons:

:::php
$fields->push(FormAction::create('sampleAction', 'Perform Sample Action'));

Summary

In a few lines of code, we've customised the look and feel of the CMS.

While this example is only scratching the surface, it includes most building blocks and concepts for more complex extensions as well.

26 KiB Raw Blame History

How to extend the CMS interface

Introduction

Redux Devtools

Overload a CMS template

Include custom CSS in the CMS

Create a "bookmark" flag on pages

Retrieve the list of bookmarks from the database

Extending the CMS actions

React components

A few words about ES6

Using dependencies within your component

Customising React components

A simple higher order component

Using the injector to customise a core component

Getting multiple customisations to work together

Using the * flag

Helpful tip: Name your higher order components

Dealing with events

Registering new React components

Using the injector directly within your component

Interfacing with legacy CMS JavaScript

Getting data into a component

Getting data out of a component

Implementing handlers

Summary

Related

26 KiB

Raw Blame History