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232 lines
6.9 KiB
Markdown
232 lines
6.9 KiB
Markdown
# Customising React Components
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In this tutorial, we'll customise some form elements rendered with React to have some new features.
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## An enhanced TextField
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Let's add a character count to the `TextField` component. `TextField` is a built-in component in the admin area. Because the `TextField` component is fetched
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through Injector, we can override it and augment it with our own functionality.
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First, let's create our [higher order component](../07_ReactJS_Redux_and_GraphQL.md#customising-react-components-with-injector).
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__my-module/js/components/CharacterCounter.js__
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```js
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import React from 'react';
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const CharacterCounter = (TextField) => (props) => {
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return (
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<div>
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<TextField {...props} />
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<small>Character count: {props.value.length}</small>
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</div>
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);
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}
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export default CharacterCounter;
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```
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Now let's add this higher order component to []Injector](../07_ReactJS_Redux_and_GraphQL.md#the-injector-api).
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__my-module/js/main.js__
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```js
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import Injector from 'lib/Injector';
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import CharacterCounter from './components/CharacterCounter';
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Injector.transform('character-count-transform', (updater) => {
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updater.component('TextField', CharacterCounter);
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});
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```
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The last thing we'll have to do is [transpile our code](../06_Javascript_Development.md#es6-and-build-tools) and load the resulting bundle file
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into the admin page.
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__my-module/\_config/config.yml__
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```yaml
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---
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Name: my-module
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---
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SilverStripe\Admin\LeftAndMain:
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extra_requirements_javascript:
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# The name of this file will depend on how you've configured your build process
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- 'my-module/js/dist/main.bundle.js'
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```
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Now that the customisation is applied, our text fields look like this:
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![](../../../_images/react-di-1.png)
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### More enhancements
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Let's add another customisation to TextField. If the text goes beyond a specified
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length, let's throw a warning in the UI.
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__my-module/js/components/TextLengthChecker.js__
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```js
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const TextLengthCheker = (TextField) => (props) => {
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const {limit, value } = props;
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const invalid = limit !== undefined && value.length > limit;
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return (
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<div>
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<TextField {...props} />
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{invalid &&
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<span style={{color: 'red'}}>
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{`Text is too long! Must be ${limit} characters`}
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</span>
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}
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</div>
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);
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}
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export default TextLengthChecker;
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```
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We'll apply this one to the injector as well, but let's do it under a different name.
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For the purposes of demonstration, let's imagine this customisation comes from another
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module.
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__my-module/js/main.js__
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```js
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import Injector from 'lib/Injector';
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import TextLengthChecker from './components/TextLengthChecker';
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Injector.transform('text-length-transform', (updater) => {
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updater.component('TextField', TextLengthChecker);
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});
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```
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Now, both components have applied themselves to the textfield.
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![](../../../_images/react-di-2.png)
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### Getting the customisations to work together
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Both these enhancements are nice, but what would be even better is if they could
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work together collaboratively so that the character count only appeared when the user
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input got within a certain range of the limit. In order to do that, we'll need to be
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sure that the `TextLengthChecker` customisation is loaded ahead of the `CharacterCounter` customisation.
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First let's update the character counter to show characters _remaining_, which is
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much more useful. We'll also update the API to allow a `warningBuffer` prop. This is
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the amount of characters the input can be within the `limit` before the warning shows.
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__my-module/js/components/CharacterCounter.js__
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```js
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import React from 'react';
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const CharacterCounter = (TextField) => (props) => {
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const { warningBuffer, limit, value: { length } } = props;
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const remainingChars = limit - length;
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const showWarning = length + warningBuffer >= limit;
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return (
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<div>
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<TextField {...props} />
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{showWarning &&
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<small>Characters remaining: {remainingChars}</small>
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}
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</div>
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);
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}
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export default CharacterCounter;
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```
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Now, when we apply this customisation, we need to be sure it loads _after_ the length
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checker in the middleware chain, as it relies on the prop `limit`.
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For this example, we'll imagine these two enhancements come from different modules.
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__module-a/js/main.js__
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```js
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import Injector from 'lib/Injector';
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import CharacterCounter from './components/CharacterCounter';
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Injector.transform(
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'character-count-transform',
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(update) => update.component('TextField', CharacterCounter),
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{ after: 'text-length-transform' }
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);
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```
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__module-b/js/main.js__
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```js
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import Injector from 'lib/Injector';
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import TextLengthChecker from './components/TextLengthChecker';
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Injector.transform(
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'text-length-transform',
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(updater) => updater.component('TextField', TextLengthChecker),
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{ before: 'character-count-transform' }
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);
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```
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Now, both components, coming from different modules, play together nicely, in the correct order.
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![](../../../_images/react-di-3.png)
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### Adding context
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We've successfully changed the behaviour and UI of our `TextField` component using two
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different two separate higher order components. By default, these are *global changes*. That is,
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every text field rendered by React will receive the enhancements we've put into the injector. Though
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this may sometimes be useful, more often than not, we only want to add our enhancements in certain
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contexts. You may, for instance, only want your character counter to display on one specific field
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in one specific form.
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Let's apply our transformation to just the file edit form in AssetAdmin.
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__my-module/js/main.js__
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```js
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import Injector from 'lib/Injector';
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import TextLengthChecker from './components/TextLengthChecker';
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Injector.transform('text-length-transform', (updater) => {
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updater.component('TextField.AssetAdmin.FileEditForm', TextLengthChecker);
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});
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```
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## A better form action: dealing with events
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Let's make a new customisation that customises the behaviour of a button. We'll have
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all form actions throw a `window.confirm()` message before executing their action. Further,
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we'll apply some new style to the button if it is in a loading state.
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__my-module/js/components/ConfirmingFormButton.js__
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```js
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import React from 'react';
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export default (FormAction) => (props) => {
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const newProps = {
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...props,
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data: {
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...props.data,
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buttonStyle: props.loading ? 'danger' : props.data.buttonStyle
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},
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handleClick(e) {
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if(window.confirm('Did you really mean to click this?')) {
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props.handleClick(e);
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}
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}
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}
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return <FormAction {...newProps} />
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}
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```
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__my-module/js/main.js__
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```js
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import ConfirmingFormButton from './components/ConfirmingFormButton';
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Injector.transform('confirming-button-transform', (updater) => {
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updater.component('FormAction', ConfirmingFormButton, 'ConfirmingFormButton');
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});
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```
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Now, when you click on any form action, it will throw a confirm window before firing its given click handler.
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