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title: React, Redux, and GraphQL summary: Learn how to extend and customise the technologies we use for application state and client-rendered UI.
Introduction to the "React" layer
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.
There are some several members of this ecosystem that all work together to provide a dyanamic UI. They include:
- ReactJS - A Javascript UI library
- Redux - A state manager for Javascript
- GraphQL - A query language for your API
- Apollo - A framework for using GraphQL in your application
All of these pillars of the frontend application can be customised, giving you more control over how the admin interface looks, feels, and behaves.
First, a brief summary of what each of these are:
React
React's job is to render UI. Its UI elements are known as "components" and represent the fundamental building block of a React-rendered interface. A React 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.
Recommended: React Dev Tools
The React Dev Tools extension available for Chrome and Firefox is critical to debugging a React UI. It will let you browse the React UI much like the DOM, showing the tree of rendered components and their current props and state in real time.
Redux
Redux is a state management tool with a tiny API that affords the developer highly predictable behaviour. All of the application state is stored in a single object, and the only way to mutate that object is by calling an action, which is just a simple object that describes what happened. A function known as a reducer mutates the state based on that action and returns a new reference with the updated state.
The following example is taken from the Redux Github page:
// reducer
function counter(state = 0, action) {
switch (action.type) {
case 'INCREMENT':
return state + 1;
case 'DECREMENT':
return state - 1;
default:
return state
}
}
let store = createStore(counter);
store.subscribe(() =>
console.log(store.getState())
);
// Call an action
store.dispatch({ type: 'INCREMENT' });
// 1
Recommended: 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.
GraphQL and Apollo
GraphQL is a strictly-typed query language that allows you to describe what data you want to fetch from your API. Because it is based on types, it is self-documenting and predictable. Further, it's structure lends itself nicely to fetching nested objects. Here is an example of a simple GraphQL query:
query GetUser($ID: Int!) {
user {
name
email
blogPosts {
title
comments(Limit: 5) {
author
comment
}
}
}
}
The above query is almost self-descriptive. It gets a user by ID, returns his or her name and email address, along with the title of any blog posts he or she has written, and the first five comments for each of those. The result of that query is, very predictably, JSON that takes on the same structure.
{
"user": {
"name": "Test user",
"email": "test@example.com",
"blogPosts": [
{
"title": "How to be awesome at GraphQL",
"comments": [
{
"author": "Uncle Cheese",
"comment": "Nice stuff, bro"
}
]
}
]
}
}
On its own, GraphQL offers nothing functional, as it's just a query language. You still need a service that will invoke queries and map their results to UI. For that, SilverStripe uses an implementation of Apollo that works with React.
For more information
This documentation will stop short of explaining React, Redux, and GraphQL/Apollo in-depth, as there is much better documentation available all over the web. We recommend:
The Injector API
Much like SilverStripe's Injector API in PHP,
the client-side framework has its own implementation of dependency injection
known as Injector
. Using Injector, you can register new services, and
transform existing services.
Injector is broken up into three sub-APIs:
Injector.component
for React UI componentsInjector.reducer
for Redux state managementInjector.form
for forms rendered viaFormSchema
.
The frontend Injector works a bit differently than its backend counterpart. Instead of overriding a service with your own implementation, you enhance an existing service with your own concerns. This pattern is known as middleware.
Middleware works a lot like a decorator. It doesn't alter the original API of the service, but it can augment it with new features and concerns. 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 middleware example
Let's say you have an application that features error logging. By default, the error logging service simply outputs to console.error
. But you want to customise it to send errors to a thirdparty service. For this, you could use middleware to augment the default functionality of the logger.
LoggingService.js
const LoggingService = (error) => console.error(error);
export default LoggingService;
Now, let's add some middleware to that service. The signature of middleware is:
const middleware = (next) => (args) => next(args);
Where next()
is the next customisation in the "chain" of middleware. Before invoking the next implementation, you can add whatever customisations you need. Here's how we would use middleware to enhance LoggingService
.
import thirdPartyLogger from 'third-party-logger';
const addLoggingMiddleware = (next) => (error) => {
if (error.type === LoggingService.CRITICAL) {
thirdpartyLogger.send(error.message);
}
return next(error);
}
Then, we would create a new logging service that merges both implementations.
import LoggingService from './LoggingService';
import addLoggingMiddleware from './addLoggingMiddleware';
const MyNewLogger = addLoggingMiddleware(LoggingService);
We haven't overriden any functionality. LoggingService(error)
will still invoke console.error
, once all the middleware has run. But what if we did want to kill the original functionality?
import LoggingService from './LoggingService';
import thirdPartyLogger from 'third-party-logger';
const addLoggingMiddleware = (next) => (error) => {
// Critical errors go to a thirdparty service
if (error.type === LoggingService.CRITICAL) {
thirdPartyLogger.send(error.message);
}
// Other errors get logged, but not to our thirdparty
else if (error.type === LoggingService.ERROR) {
next(error);
}
// Minor errors are ignored
else {
// Do nothing!
}
}
Registering new services to the Injector
If you've created a module using React, it's a good idea to afford other developers an
API to enhance those components, forms, and state. To do that, simply register them with Injector
.
my-public-module/js/main.js
import Injector from 'lib/Injector';
Injector.component.register('MyComponent', MyComponent);
Injector.reducer.register('myCustom', MyReducer);
Services can then be fetched using their respective .get()
methods.
const MyComponent = Injector.component.get('MyComponent');
Transforming services using middleware
Now that the services are registered, other developers can customise your services with Injector.transform()
.
someone-elses-module/js/main.js
Injector.transform(
'my-transformation',
(updater) => {
updater.component('MyComponent', MyCustomComponent);
updater.reducer('myCustom', MyCustomReducer);
}
);
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 an updater
object. It contains four functions: component()
, reducer()
, form.alterSchema()
and form.addValidation()
. We'll cover all of these in detail functions in detail further into the document, but briefly, these update functions allow you to mutate the DI container with a wrapper for the service. Remember, this function does not replace
the service -- it enhances it with new functionality.
Helpful tip: Name your component middleware
Since multiple enhancements can be applied 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 updater.component
function. It takes an arbitrary
name for the enhancement you're applying.
module-a/js/main.js
(updater) => updater.component('TextField', CharacterCounter, 'CharacterCounter')
module-b/js/main.js
(updater) => updater.component('TextField', TextLengthChecker, 'TextLengthChecker')
Controlling the order of transformations
Sometimes, it's critical to ensure that your customisation happens after another one has been executed. To afford you control over the ordering of transforms, Injector allows before
and after
attributes as metadata for the transformation.
my-module/js/main.js
Injector.transform(
'my-transformation',
(updater) => {
updater.component('MyComponent', MyCustomComponent);
updater.reducer('myCustom', MyCustomReducer);
},
{ after: 'another-module' }
);
before
and after
also accept arrays of constraints.
Injector.transform(
'my-transformation',
(updater) => updater.component('MyComponent', MyCustomComponent);
{ 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',
(updater) => updater.component('MyComponent', FinalTransform),
{ after: '*' }
);
Injector context
Because so much of UI design depends on context, dependency injection in the frontend is not necessarily universal. Instead, services are fetched with context.
example:
const CalendarComponent = Injector.get('Calendar', 'AssetAdmin.FileEditForm.StartDate');
Likewise, services can be applied for specific contexts.
Injector.transform('my-transform', (updater) => {
// Applies to all text fields in AssetAdmin
updater.component('TextField.AssetAdmin', MyTextField);
// Applies to all text fields in AssetAdmin editform
updater.component('TextField.AssetAdmin.FileEditForm', MyTextField);
// Applies to any textfield named "Title" in AssetAdmin
updater.component('TextField.AssetAdmin.*.Title', MyTextField);
// Applies to any textfield named "Title" in any admin
updater.component('TextField.*.*.Title', MyTextField);
})
To apply context-based transformations, you'll need to know the context of the component you want to customise. To learn this,
open your React Developer Tools (see above) window and inspect the component name. The
context of the component is displayed between two square brackets, appended to the original name, for example:
TextField[TextField.AssetAdmin.FileEditForm.Title]
. The context description is hierarchical, starting
with the most general category (in this case, "Admin") and working its way down to the most specific
category (Name = 'Title'). You can use Injector to hook into the level of specificity that you want.
Customising React components with Injector
When middleware is used to customise a React component, it is known as a higher order component.
Using the PhotoItem
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) => (
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 dependencies within your React 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([dependencies], mapDependenciesToProps, getContext)(Component)
- [dependencies]: An array of dependencies (or a string, if just one)
- mapDependenciesToProps: (optional) All dependencies 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.
- getContext: A callback function with params
(props, currentContext)
that will calculate the context to use for determining which tranformations apply to the dependencies. This defaults to the current context. This could help when any customisations that may calls for a change (or tweak) to the current context.
The result is a function that is ready to apply to a component.
const MyInjectedComponent = inject(
['Dependency1', 'Dependency2']
)(MyComponent);
// MyComponent now has access to props.Dependency1 and props.Dependency2
Here is its usage with a bit more context:
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(
['GalleryItem', 'SearchBar'],
(GalleryItem, SearchBar) => ({
ItemComponent: GalleryItem,
SearchComponent: SearchBar
}),
() => 'Gallery.Search'
)(Gallery);
The properties used by inject()
are soft-supplied. This means a parent calling a component that uses
inject()
could choose to overwrite the dependencies which inject()
would have otherwise supplied.
Here is an example using the above Gallery
component with the dependency ItemComponent
overwritten by the
calling component. We pull in a previously registered PreviewItem
to replace the former GalleryItem
.
my-module/js/components/PreviewSection.js
import React from 'react';
import { inject } from 'lib/Injector';
class PreviewSection extends React.Component {
render() {
const { Gallery, PreviewItem } = this.props;
return (
<div className="preview-section">
<div className="preview-sidebar">Sidebar here</div>
<Gallery ItemComponent={PreviewItem}/>
</div>
);
}
}
export default inject(
['Gallery', 'PreviewItem']
)(PreviewSection);
Another way to provide context to injector is by using the provideContext
HOC, rather than
the getContext
param in inject()
.
my-module/js/components/ContextualSection.js
import React, { Component } from 'react';
import { provideContext, inject } from 'lib/Injector';
class MySection extends Component {
// ... section code here ...
}
export default compose(
provideContext('Gallery.Search'),
inject(['Gallery'])
)(MySection);
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, 'Reports.context');
return <Component title={item.title} image={item.image} />
})}
</div>
}
}
export default withInjector(MyGallery);
The Reports.context
in the second parameter provides a context for the injector to determine
which transformations to apply to or remove from the component you're looking to get.
More details about transformations below.
Using Injector to customise forms
Forms in the React layer are built declaratively, using the FormSchema
API. A component called
FormBuilderLoader
is given a URL to a form schema definition, and it populates itself with fields
(both structural and data-containing) and actions to create the UI for the form. Each form is required
to have an identifier
property, which is used to create context for Injector when field components
are fetched. This affords developers the opportunity provide very surgical customisations.
Updating the form schema
Most behavioural and aesthetic customisations will happen via a mutation of the form schema. For this,
we'll use the updater.form.alterSchema()
function.
Injector.transform(
'my-custom-form',
(updater) => {
updater.form.alterSchema(
'AssetAdmin.*',
(form) =>
form.updateField('Title', {
myCustomProp: true
})
.getState()
)
}
);
The alterSchema()
function takes a callback, with an instance of FormStateManager
(form
in the
above example) as a parameter. FormStateMangaer
allows you to declaratively update the form schema
API using several helper methods, including:
updateField(fieldName:string, updates:object)
updateFields({ myFieldName: updates:object })
mutateField(fieldName:string, callback:function)
setFieldComponent(fieldName:string, componentName:string)
setFieldClass(fieldName:string, cssClassName:string, active:boolean)
addFieldClass(fieldName:string, cssClassName:string)
removeFieldClass(fieldName:string, cssClassName:string)
In addition to mutation methods, several readonly methods are available on FormSchemaManager
to read the current form state, including:
getValues()
: Returns a map of field names to their current valuesgetValue(fieldName:string)
: Returns the value of the given fieldisDirty()
: Returns true if the form has been mutated from its original stateisPristine()
: Returns true if the form is in its original stateisValid()
: Returns true if the form has no validation errorsisInvalid()
: Returns true if the form has validation errors
Adding validation to a form
Validation for React-rendered forms is handled by the redux-form package. You can inject your own middleware to add custom validation rules using the updater.form.addValidation()
function.
Injector.transform(
'my-validation',
(updater) => {
updater.form.addValidation(
'AssetAdmin.*',
(values, validator) => {
if (values.PostalCode.length !== 5) {
validator.addError('PostalCode', 'Invalid postal code');
}
}
)
}
);
The addValidation()
function takes a callback, with an instance of FormValidationManager
(validator
in the above example) as a parameter. FormValidationMangaer
allows you to manage the validation result using several helper methods, including:
addError(fieldName:string, message:string)
addErrors(fieldName:string, messages:Array)
hasError(fieldName:string)
clearErrors(fieldName:string)
getErrors(fieldName:string)
reset(void)
Using Injector to customise Redux state data
Before starting this tutorial, you should become familiar with the concepts of Immutability and Redux.
The examples use Spread in object literals which is at this moment in Stage 3 Proposal. If you're more comfortable with using
the Object.assign()
API that shouldn't present any problems and should work the same.
For example:
newProps = { ...oldProps, name: 'New name' };
is the same as
newProps = Object.assign(
{},
oldProps,
{ name: 'New name' }
);
To start customising, you'll need to transform an existing registered reducer, you can find what reducers are registered by importing Injector and running Injector.reducer.getAll()
Injector.transform('customisationName', (updater) => {
updater.reducer('assetAdmin', MyReducerTransformer);
});
As you can see, we use the reducer()
function on the update
object to augment Redux state transformations.
Using Redux dev tools
It is important to learn the basics of Redux dev tools, so that you can find out what ACTIONS and payloads to intercept and modify in your Transformer should target.
Most importantly, it helps to understand the "Action" sub-tab on the right panel (bottom if your dev tools is small), as this will be the data your Transformer will most likely receive, pending other transformers that may run before/after your one.
Structuring a transformer
We use currying to supply utilities which your transformer may require to handle the transformation.
originalReducer
- reducer callback which the transformer is customising, this will need to be called in most cases. This will also callback other transformations down the chain of execution. Not calling this will break the chain.getGlobalState
- A function that gets the state of the global Redux store. There may be data outside the current scope in the reducer which you may need to help determine the transformation.state
- current state of the current scope. This is what should be used to form the new state.type
- the action to fire, like in any reducer in Redux. This helps determine if your transformer should do anything.payload
- the new data sent with the action to mutate the Redux store.
const MyReducerTransformer = (originalReducer) => (globalState) => (state, { type, payload }) => {
switch (type) {
case 'EXISTING_ACTION': {
// recommended to call and return the originalReducer with the payload changed by the transformer
/* return action to call here; */
}
case 'OVERRIDE_EXISTING_ACTION': {
// could omit the originalReducer to enforce your change or cancel the originalREducer's change
}
default: {
// it is important to return the originalReducer with original redux parameters.
return originalReducer(state, { type, payload });
}
}
}
A basic transformation
This example we will illustrate modifying the payload to get different data saved into the original reducer.
We will rename anything in the breadcrumbs that is displaying "Files" to display "Custom Files" instead.
const MyReducerTransformer = (originalReducer) => (getGlobalState) => (state, { type, payload }) => {
switch (type) {
case 'SET_BREADCRUMBS': {
return originalReducer(state, {
type,
payload: {
breadcrumbs: payload.breadcrumbs.map((crumb) => (
(crumb.text === 'Files')
? { ...crumb, text: 'Custom Files' }
: crumb
)),
},
});
}
}
};
Using the globalState
Accessing the globalState is easy, as it is passed in as part of the curried functions definition.
export default (originalReducer) => (getGlobalState) => (state, { type, payload }) => {
const baseUrl = globalState.config.baseUrl;
switch (type) {
/* ... cases here ... */
}
}
Setting a different initial state
We can easily define a new initial state by providing the state
param with a default value.
It is recommended to keep the call for the original initialState for your initialState then override values, so that you do not lose any potentially critical data that would have originally been set.
const MyReducerTransformer = (originalReducer) => () => (state, { type, payload }) => {
if (typeof state === 'undefined') {
return {
...originalReducer(state, { type, payload }),
myCustom: 'initial state here',
};
}
};
Cancelling an action
There are valid reasons to break the chain of reducer transformations, such as cancelling the Redux store update. However, like an original reducer in redux, you will still need to return the original state.
export default (originalReducer) => (getGlobalState) => (state, { type, payload }) => {
switch (type) {
case 'CANCEL_THIS_ACTION': {
return state;
}
}
};
Calling a different action
You could manipulate the action called by the originalReducer, there isn't an example available but this block of code will present the theory of how it can be achieved.
default (originalReducer) => (getGlobalState) => (state, { type, payload }) => {
switch (type) {
case 'REMOVE_ERROR': {
// we'd like to archive errors instead of removing them
return originalReducer(state, {
type: 'ARCHIVE_ERROR',
payload,
});
}
}
};
Using Injector to customise GraphQL queries
One of the strengths of GraphQL is that it allows us to declaratively state exactly what data a given component needs to function. Because GraphQL queries and mutations are considered primary concerns of a component, they are not abstracted away somewhere in peripheral asynchronous functions. Rather, they are co-located with the component definition itself.
The downside of this is that, because queries are defined statically at compile time, they don't adapt well to the extension patterns that are inherent to SilverStripe projects. For instance, a query for a Member record may include fields for FirstName
and Email
, but if you have customised that class via extensions, and would like the component using that query to display your custom fields, your only option is to override the entire query and the component with a custom implementation. In backend code, this would be tantamount to replacing the entire Member
class and SecurityAdmin
section just because you had a new field. You would never do that, right? It's an over-aggressive hack! We need APIs that make extension easy.
To that end, the Injector
library provides a container for abstract representations of GraphQL queries and mutations. You can register and transform them as you do components and reducers. They exist merely as abstract concepts until Injector
loads, at which time all transformations are applied, and each registered query and mutation is composed and attached to their assigned components.
Extensions are only as good as the code they're extending
An important point to remember about these types of deep customisations is that they all depend heavily on the core code they're modifying to follow specific patterns. The more the core code makes use of Injector
the easier it will be for third party developers to extend. Conversely, if the core is full of hard-coded component definitions and statically written queries, customisation will be at best less surgical and at worst, not possible. For this reason, we'll look at GraphQL customisations from two sides -- making code extensible, and then extending that code.
Building an extensible GraphQL app
Let's imagine that we have a module that adds a tab where the user can write "notes" about the content he or she is editing. We'll use GraphQL and React to render this UI. We have a dataobject called "Note" where we store these in the database.
Here's what that might look like:
import React from 'react';
import gql from 'graphql-tag';
import { graphql } from 'apollo-client';
const Notes = ({ notes }) => (
<ul className="notes">
{notes.map(note => <li key={note.ID}>{note.Content}</li>)}
</ul>
);
const getNotesQuery = gql`
query ReadNotes {
readNotes {
ID
Title
}
}
`;
const apolloConfig = {
props({ data: { readNotes } }) {
return {
notes: readNotes
};
}
};
const NotesWithData = graphql(getNotesQuery, apolloConfig)(Notes);
export default NotesWithData;
Lastly, we'll expose the model to GraphQL:
SilverStripe\GraphQL\Controller:
schema:
scaffolding:
types:
MyApp\AwesomeNotes\Note:
fields: [ID, Content]
operations:
read:
paginate: false
create: true
What we've just built may work, but we've made life very difficult for other developers. They have no way of customising this. Let's change that.
Register as much as possible with Injector
The best thing you can do to make your code extensible is to use Injector
early and often. Anything that goes through Injector is easily customisable.
First, let's break up the list into smaller components.
myapp/client/components/NotesList.js
import React from 'react';
import { inject } from 'lib/Injector';
const NotesList = ({ notes = [], ItemComponent }) => (
<ul className="notes">
{notes.map(note => <ItemComponent key={note.ID} note={note} />)}
</ul>
);
export default inject(
['NotesListItem'],
(NotesListItem) => ({
ItemComponent: NotesListItem
})
)(NotesList);
myapp/client/components/NotesListItem.js
import React from 'react';
const NotesListItem = ({ note }) => <li>{note.Content}</li>;
export default NotesListItem;
Creating an abstract query definition
The next piece is the query. We'll need to register that with Injector
. Unlike components and reducers, this is a lot more abstract. We're actually not going to write any GraphQL at all. We'll just build the concept of the query in an abstraction layer, and leave Injector
to build the GraphQL syntax at runtime.
myapp/client/readNotes.js
import { graphqlTemplates } from 'lib/Injector';
const { READ } = graphqlTemplates;
const query = {
apolloConfig: {
props({ data: { readNotes } }) {
return {
notes: readNotes,
}
}
},
templateName: READ,
pluralName: 'Notes',
pagination: false,
params: {},
fields: [
'Content',
'ID'
],
};
export default query;
Dynamic GraphQL queries are generated by populating pre-baked templates with specific pieces of data, including fields, fragments, variables, parameters, and more. By default, the templates available to you follow the GraphQL scaffolding API (readMyObjects
, readOneMyObject
, createMyObject
, deleteMyObject
, and updateMyObject
).
In this example, we're using the READ
template, which needs to know the plural name of the object (e.g. readNotes
), whether pagination is activated, and which fields you want to query.
Register all the things
Let's now register all of this with Injector.
myapp/client/registerDependencies.js
import NotesList from './NotesList';
import NotesListItem from './NotesListItem';
import readNotes from './readNotes';
import Injector, { injectGraphql } from 'lib/Injector';
const registerDependencies = () => {
Injector.component.register('NotesList', NotesList);
Injector.component.register('NotesListItem', NotesListItem);
Injector.query.register('ReadNotes', readNotes);
};
export default registerDependencies;
We use Injector.query.register
to register our readNotes
query as extensible.
Applying the injected query as a transformation
The only missing piece now is to attach the ReadNotes
injected query to the NotesList
component. We could have done this using injectGraphql
in the NotesList
component itself, but instead, we'll do it as an Injector transformation. Why? There's a good chance whoever is customising the query will want to customise the UI of the component that is using that query. If someone adds a new field to a query, it is likely the component should display that new field. Registering the GraphQL injection as a transformation will allow a thirdparty developer to override the UI of the component explicitly after the GraphQL query is attached. This is important, because otherwise, the component override would not be wired up to your data source.
myapp/client/registerDependencies.js
// ...
const registerDependencies = () => {
// ...
Injector.transform(
'noteslist-graphql',
(updater) => {
updater.component('NotesList', injectGraphql('ReadNotes'));
}
);
};
export default registerDependencies;
The transformation adds the higher-order component injectGraphQL
, using the query we have just registered, ReadNotes
as a dependency.
All of this feels like a lot of extra work, and, to be fair, it is. You're probably used to simply inlining one or many higher-order component compositions in your components. That works great when you're not concerned about making your components extensible, but if you want others to be able to customise your app, you really need to be sure to follow these steps.
Define the app
Let's make a really simple container app that calls NotesList
as a dependency.
myapp/client/App.js
import React from 'react';
import { inject } from 'lib/Injector';
const App = ({ ListComponent }) => (
<div>
<h3>Notes</h3>
<ListComponent />
</div>
);
export default inject(
['NotesList'],
(NotesList) => ({
ListComponent: NotesList,
})
)(App);
You can register this with Injector
, too, but since it's already injected with dependencies, it could get pretty convoluted. High level components like this are best left uncustomisable.
Bootstrap and mount
Since almost everything is in Injector
now, our mounting code is pretty trivial.
myapp/client/index.js
import { render } from 'react-dom';
import React from 'react';
import registerDependencies from './registerDependencies';
import { ApolloProvider } from 'react-apollo';
import Injector, { InjectorProvider, provideInjector, inject } from 'lib/Injector';
import App from './App';
registerDependencies();
Injector.ready(() => {
const { apolloClient, store } = window.ss;
const MyApp = () => (
<ApolloProvider client={apolloClient} store={store}>
<App />
</ApolloProvider>
);
const MyAppWithInjector = provideInjector(MyApp);
$('#notes-app').entwine({
onmatch() {
render(
<MyAppWithInjector />,
this[0]
)
}
})
});
We register a callback with Injector
to ensure that we don't attempt to render anything before the transformations have been applied. This would result in fatal errors, so be sure to wrap your mounting code in Injector.ready()
.
The silverstripe/admin
module was generous enough to hang its apolloClient
and store
objects in the global namespace to be shared by other modules. We'll make use of those, and create our own app wrapped in <ApolloProvider />
. We then make our app Injector
aware by wrapping it with the provideInjector
higher-order component.
To mount the app, we use the onmatch()
event fired by entwine, and we're off and running.
Extending an existing GraphQL app
Let's suppose we have our own module that extends the Notes
object in some way. Perhaps we have a Priority
field whose value alters the UI in some way. Thanks to a module developer who gave use plenty of extension points through Injector
, this will be pretty easy.
Applying the extensions
We'll first need to apply the extension and update our GraphQL scaffolding.
MyApp\AwesomeNotes\Note:
extensions:
# this extension adds a "Priority" field
- MyOtherApp\NastyNotes\NoteExtension
SilverStripe\GraphQL\Controller:
schema:
scaffolding:
types:
MyApp\AwesomeNotes\Note:
fields: [ Priority ]
Creating transforms
Let's first update the NotesListItem
to contain our new field.
my-other-app/client/transformNotesListItem.js
import React from 'react';
const transformNotesListItem = () => ({ note: { Content, Priority } }) => (
<li className={`priority-${Priority}`}>{Content} [PRIORITY: {Priority}]</li>
);
export default transformNotesListItem;
Now, let's update the query to fetch our new field.
my-other-app/client/transformReadNotes.js
const transformReadNotes = (manager) => {
manager.addField('root', 'Priority');
};
export default transformReadNotes;
Simple! The transformation passes us a ApolloGraphQLManager
instance that provides a fluent API for updating a query definition the same way the FormStateManager
allows us to update Redux form state.
Adding fields
In the above example, we added a single field to a query. Here's how that works:
manager.addField(fieldPath, fieldName)
The fieldPath
argument tells the manager at what level to add the field. In this case, since the Priority
field is going on the root query (readNotes
), we'll use root
as the path. But suppose we had a more complex query like this:
query readMembers {
FirstName
Surname
Friends {
Email
Company {
Name
}
}
}
If we wanted to add a field to the nested Company
query on Friends
, we would use a path syntax.
manager.addField('root/Friends/Company', 'Tagline');
Adding field arguments
Let's suppose we had the following query:
query ReadMembers($ImageSize: String!) {
readMembers {
FirstName
Avatar(Size: $ImageSize)
Company {
Name
}
}
}
Maybe the Company
type has a Logo
, and we want to apply the ImageSize
parameter as an argument to that field.
manager.addArg('root/Company/Logo', 'Size', 'ImageSize');
Where root/Company/Logo
is the path to the field, Size
is the name of the argument on that field, and ImageSize
is the name of the variable.
Applying the transforms
Now, let's apply all these transformations, and we'll use the after
property to ensure they get applied in the correct sequence.
import Injector, { injectGraphql } from 'lib/Injector';
import transformNotesListItem from './transformNotesListItem';
import transformReadNotes from './transformReadNotes';
Injector.transform(
'noteslist-query-extension',
(updater) => {
updater.component('NotesListItem', transformNotesListItem);
updater.query('ReadNotes', transformReadNotes);
},
{ after: 'noteslist-graphql' }
);
Creating extensible mutations
Let's now add an AddForm
component to our list that lets the user create a new note.
myapp/client/App.js
import React from 'react';
import { inject } from 'lib/Injector';
const App = ({ ListComponent, AddComponent }) => (
<div>
<h3>Notes</h3>
<ListComponent />
<AddComponent />
</div>
);
export default inject(
['NotesList','NoteAddForm'],
(NotesList, NoteAddForm) => ({
ListComponent: NotesList,
AddComponent: NoteAddForm,
})
)(App);
And we'll create some UI for that AddComponent
.
myapp/client/AddForm.js
import React from 'react';
const AddForm = ({ onAdd }) => {
let input;
return (
<div>
<label>New note</label>
<input type="text" ref={node => input = node}/>
<button onClick={(e) => {
e.preventDefault();
onAdd(input && input.value);
}}>Add</button>
</div>
);
};
export default AddForm;
Next, a mutation to attach to the form.
myapp/cient/createNote.js
import { graphqlTemplates } from 'lib/Injector';
const { CREATE } = graphqlTemplates;
const mutation = {
apolloConfig: {
props({ mutate }) {
return {
onAdd: (content) => {
mutate({
variables: {
Input: {
Content: content,
}
}
});
}
}
}
},
templateName: CREATE,
singularName: 'Note',
pagination: false,
params: {},
fields: [
'Content',
'ID'
],
};
export default mutation;
It looks like a lot of code, but if you're familiar with Apollo mutations, this is pretty standard. The supplied mutate
function gets mapped to a prop -- in this case onAdd
, which the AddForm
component is configured to invoke. We've also supplied the singularName
as well as the template CREATE
for the createNote
scaffolded mutation.
Lastly, let's just register all this with Injector
.
myapp/client/registerDependencies.js
//...
import AddForm from './AddForm';
import createNote from './createNote';
const registerDependencies = () => {
//...
Injector.component.register('NoteAddForm', AddForm);
Injector.query.register('CreateNote', createNote);
//...
Injector.transform(
'notesaddform-graphql',
(updater) => {
updater.component('NoteAddForm', injectGraphql('CreateNote'));
}
);
};
export default registerDependencies;
This is exactly the same pattern as we did before with a query, only with different components and GraphQL abstractions this time. Note that even though CreateNote
is a mutation, it still gets registered under Injector.query
for simplicity.
Extending mutations
Now let's switch back to our thirdparty module that is customising our Notes application. The developer is going to want to ensure that users can supply a "Priority" value for each note entered. This will involve updating the AddForm
component.
my-other-app/client/transformAddForm.js
import React from 'react';
const transformAddForm = () => ({ onAdd }) => {
let content, priority;
return (
<div>
<label>Note content</label>
<input type="text" ref={node => content = node}/>
<label>Priority</label>
<select ref={node => priority = node}>
<option value="low">Low</option>
<option value="medium">Medium</option>
<option value="high">High</option>
</select>
<button onClick={(e) => {
e.preventDefault();
if (content && priority) {
onAdd(content.value, priority.value);
}
}}>Add</button>
</div>
);
};
export default transformAddForm;
We've extended the onAdd
callback to take two parameters -- one for the note content, and another for the priority. We'll need to update the mutation to reflect this.
my-other-app/client/transformCreateNote.js
const transformCreateNote = (manager) => {
manager.addField('root', 'Priority');
manager.transformApolloConfig('props', ({ mutate }) => (prevProps) => {
const onAdd = (content, priority) => {
mutate({
variables: {
Input: {
Content: content,
Priority: priority
}
}
});
};
return {
...prevProps,
onAdd,
};
})
};
export default transformCreateNote;
All we've done here is overridden the props
setting in the CreateNote
apollo config. Recall from the previous section that it maps the mutate
function to the onAdd
prop. Since we've changed the signature of that function, we'll need to override the entire prop.
Now we just need to register these transforms, and we're done!
//...
import transformAddForm from './transformAddForm';
import transformCreateNote from './transformCreateNote';
Injector.transform(
'noteslist-query-extension',
(updater) => {
//...
updater.component('NoteAddForm', transformAddForm);
updater.query('CreateNote', transformCreateNote);
},
{ after: ['noteslist-graphql', 'notesaddform-graphql'] }
);