ember-statecharts

This addon provides a statechart abstraction based on XState for adding statecharts to your Ember.js application. Statecharts can be used to describe complex behaviour of your objects and separate ui-concern from behavioral concerns in your applications. This is especially useful in Ember.Component-architecture but can be used across all layers of your application (e.g. when implementing global application state).

View the docs here.

Compatibility

• Ember.js v3.24 or above
• Ember CLI v3.20 or above
• Node.js v12 or above

For classic Ember.js-versions pre Ember Octane please use the 0.8.x-version of this addon.

For Ember.js versions < 3.24 please use the 0.13.x-version of this addon.

Installation

ember install ember-statecharts

Because ember-statecharts works with XState internally you have to install it as a dependency as well.

yarn add --dev xstate

or

npm install --save-dev xstate

Usage

Statecharts have been around for a long time and have been used to model stateful, reactive system successfully. You can read about statecharts in the original paper Statecharts - A Visual Formalism for Complex Systems by David Harel.

With statecharts we finally have a good abstraction to model and discuss behaviour with other stakeholders of our applications in addition to a design language that visualizes this behaviour. Here's an example of a button component:

In addition to their modeling capabilities Statecharts are executable and can be used to drive user experience behavior in your Ember.js applications:

import Component from '@glimmer/component';
import { action } from '@ember/object';
import { task } from 'ember-concurrency';

import { matchesState, useMachine } from 'ember-statecharts';
import { Machine } from 'xstate';

function noop() {}

const buttonMachine = Machine(
  {
    initial: 'idle',
    states: {
      idle: {
        on: {
          SUBMIT: 'busy',
        },
      },
      busy: {
        entry: ['handleSubmit'],
        on: {
          SUCCESS: 'success',
          ERROR: 'error',
        },
      },
      success: {
        entry: ['handleSuccess'],
        on: {
          SUBMIT: 'busy',
        },
      },
      error: {
        entry: ['handleError'],
        on: {
          SUBMIT: 'busy',
        },
      },
    },
  },
  {
    actions: {
      handleSubmit() {},
      handleSuccess() {},
      handleError() {},
    },
  }
);

export default class QuickstartButton extends Component {
  get onClick() {
    return this.args.onClick || noop;
  }

  statechart = useMachine(this, () => {
    const { performSubmitTask, onSuccess, onError } = this;

    return {
      machine: quickstartButtonMachine.withConfig({
        actions: {
          handleSubmit: performSubmitTask,
          handleSuccess: onSuccess,
          handleError: onError,
        },
      }),
    };
  });

  @matchesState('busy')
  isBusy;

  get isDisabled() {
    return this.isBusy || this.args.disabled;
  }

  @task(function* () {
    try {
      const result = yield this.onClick();
      this.statechart.send('SUCCESS', { result });
    } catch (e) {
      this.statechart.send('ERROR', { error: e });
    }
  })
  handleSubmitTask;

  @action
  handleClick() {
    this.statechart.send('SUBMIT');
  }

  @action
  onSuccess(_context, { result }) {
    return (this.args.onSuccess && this.args.onSuccess(result)) || noop();
  }

  @action
  onError(_context, { error }) {
    return (this.args.onError && this.args.onError(error)) || noop();
  }

  @action
  performSubmitTask() {
    this.handleSubmitTask.perform();
  }
}

Please refer to the documentation page for a detailed guide of how you can use statecharts to improve your Ember.js application architecture.

Contributing

See the Contributing guide for details.

License

This project has been developed by https://www.effective-ember.com/ and contributors. It is licensed under the MIT License.