Lifecycle

How to hook into Reflex activity... aka callbacks

Client-Side Reflex Callbacks

StimulusReflex gives you the ability to inject custom Javascript at four distinct moments around sending an event to the server and updating the DOM. These hooks allow you to improve the user experience and handle edge cases.

before - prior to sending a request over the web socket
success - after the server-side Reflex succeeds and the DOM has been updated
error - whenever the server-side Reflex raises an error
after - after both success and error

Using lifecycle callback methods is not a requirement.

Think of them as power tools that can help you build more sophisticated results. 👷

If you define a method with a name that matches what the library searches for, it will run at just the right moment. If there's no method defined, nothing happens. StimulusReflex will only look for these methods in Stimulus controllers that have called StimulusReflex.register(this) in their connect() function.

There are two kinds of callback methods: generic and custom. Generic callback methods are invoked for every Reflex action on a controller. Custom callback methods are only invoked for specific Reflex actions.

StimulusReflex also emits lifecycle events which can be captured in other Stimulus controllers, jQuery plugins or even the console.

Generic Lifecycle Methods

StimulusReflex controllers can define up to four generic lifecycle callback methods. These methods fire for every Reflex action handled by the controller.

beforeReflex
reflexSuccess
reflexError
afterReflex

templates/show.html

<div data-controller="example">
  <a href="#" data-reflex="ExampleReflex#update">Update</a>
  <a href="#" data-reflex="ExampleReflex#delete">Delete</a>
</div>

javascript/controllers/example_controller.js

import { Controller } from 'stimulus'
import StimulusReflex from 'stimulus_reflex'

export default class extends Controller {
  connect () {
    StimulusReflex.register(this)
  }

  beforeReflex(anchorElement) {
    const { reflex } = anchorElement.dataset
    if (reflex.match(/update$/)) anchorElement.innerText = 'Updating...'
    if (reflex.match(/delete$/)) anchorElement.innerText = 'Deleting...'
  }
}

In this example, we update each anchor's text before invoking the server side Reflex.

Custom Lifecycle Methods

StimulusReflex controllers can define up to four custom lifecycle callback methods for each Reflex. These methods use a naming convention based on the name of the Reflex. For example, the Reflex ExampleReflex#update will cause StimulusReflex to check for the existence of the following lifecycle callback methods:

beforeUpdate
updateSuccess
updateError
afterUpdate

templates/show.html

<div data-controller="example">
  <a href="#" data-reflex="ExampleReflex#update">Update</a>
  <a href="#" data-reflex="ExampleReflex#delete">Delete</a>
</div>

javascript/controllers/example_controller.js

import { Controller } from 'stimulus'
import StimulusReflex from 'stimulus_reflex'

export default class extends Controller {
  connect () {
    StimulusReflex.register(this)
  }

  beforeUpdate(anchorElement) {
    anchorElement.innerText = 'Updating...'
  }

  beforeDelete(anchorElement) {
    anchorElement.innerText = 'Deleting...'
  }
}

Adapting the Generic example, we've refactored our controller to capture the before callback events for each anchor individually.

It's not required to implement all lifecycle methods. Pick and choose which lifecycle callback methods make sense for your application. The answer is frequently none.

Conventions

Method Names

Lifecycle callback methods apply a naming convention based on your Reflex actions. For example, the Reflex ExampleReflex#do_stuff will produce the following camel-cased lifecycle callback methods.

beforeDoStuff
doStuffSuccess
doStuffError
afterDoStuff

Method Signatures

Both generic and custom lifecycle callback methods share the same arguments:

beforeReflex(element, reflex)
reflexSuccess(element, reflex)
reflexError(element, reflex, error)
afterReflex(element, reflex, error)

element - the DOM element that triggered the Reflex this may not be the same as the controller's this.element

reflex - the name of the server-side Reflex

error - the error message if an error occurred, otherwise null

Lifecycle Events

If you need to know when a Reflex method is called, but you're working outside of the Stimulus controller that initiated it, you can subscribe to receive DOM events.

DOM events are limited to the generic lifecycle; developers can obtain information about which Reflex methods were called by inspecting the detail object when the event is captured.

Events are dispatched on the same element that triggered the Reflex. Events bubble but cannot be cancelled.

Event Names

stimulus-reflex:before
stimulus-reflex:success
stimulus-reflex:error
stimulus-reflex:after

Event Metadata

When an event is captured, you can obtain all of the data required to respond to a Reflex action:

document.addEventListener('stimulus-reflex:before', event => {
  event.target // the element that triggered the Reflex (may not be the same as controller.element)
  event.detail.reflex // the name of the invoked Reflex
  event.detail.controller // the controller that invoked the stimuluate method
})

event.target is a reference to the element that triggered the Reflex, and event.detail.controller is a reference to the instance of the controller that called the stimulate method. This is especially handy if you have multiple instances of a controller on your page.

Knowing which element dispatched the event might appear daunting, but the key is in knowing how the Reflex was created. If a Reflex is declared using a data-reflex attribute in your HTML, the event will be emitted by the element with the attribute.

If you're calling the stimulate method inside of a Stimulus controller, the event will be emitted by the element the data-controller attribute is declared on.

Promises

Are you a hardcore Javascript developer? Then you'll be pleased to know that in addition to lifecycle methods and events, StimulusReflex allows you to write promise resolver functions:

this.stimulate('MyReflex#action')
  .then(() => this.doSomething())
  .catch(() => this.handleError())

You can get a sense of the possibilities:

this.stimulate('MyReflex#example')
  .then(payload => {
    const { data, element, event } = payload
    const { attrs, reflexId } = data
    // * attrs - an object that represents the attributes of the element that triggered the reflex
    // * data - the data sent from the client to the server over the web socket to invoke the reflex
    // * element - the element that triggered the reflex
    // * event - the source event
    // * reflexId - a unique identifier for this specific reflex invocation
  })
  .catch(payload => {
    const { data, element, event } = payload
    const { attrs, reflexId } = data
    const { error } = event.detail.stimulusReflex
    // * attrs - an object that represents the attributes of the element that triggered the reflex
    // * data - the data sent from the client to the server over the web socket to invoke the reflex
    // * element - the element that triggered the reflex
    // * error - the error message from the server
    // * event - the source event
    // * reflexId - a unique identifier for this specific reflex invocation
  })

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Last updated 4 years ago

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