ember-stateful-promise

ember-concurrency is the go to solution in the Ember community for tracking async action state and many other tasks around async behaviour.

ember-stateful-promise seeks to simplify with native async/await instead of generators and expose a few flags on a promise object for you to use. Moreover, they are tracked! This library can be used if you simply need derived state your async functions and/or need a lightweight version of ember-concurrency.

Also ember-promise-helpers is another great library if you want to calculate state from your promises. ember-stateful-promise is different in that is seeks to provide derived state.

Lastly, if you already use ember-concurrency but rather author with async/await, ember-concurrency-async is available as a babel build time plugin. Again, you just need to weigh the tradeoffs (size, complexity) for your project.

API

Supports

1. Derived state
2. Debouncing async functions
3. Cleanup of async functions wired up with @ember/destroyable

• isRunning
• isResolved
• isError
• isCanceled
• performCount
• cancel() // this.clickMe.cancel()

Usage

There are a few ways to use this addon. Likely, you only need the stateful-function decorator. However, if you need the lower level util, we make that available as StatefulPromise as well.

Decorator

import Component from '@glimmer/component';
import { action } from '@ember/object';
import { statefulFunction } from 'ember-stateful-promise/decorators/stateful-function';

class MyComponent extends Component {
    @statefulFunction
    async clickMe() {
        await fetch(url);
    }
}

<button
  disabled={{if this.clickMe.isRunning "true"}}
  {{on "click" this.clickMe}}>
    Click 
</button>
<p>(Clicked this many times - {{this.clickMe.performCount}})</p>

Note - the default behaviour out of the box is to debounce the action. When clicked while a promise is outstanding, the first promise will be rejected and a new promise will be created.

To throttle the function, pass { throttle: true } to the decorator arguments.

import Component from '@glimmer/component';
import { action } from '@ember/object';
import { statefulFunction } from 'ember-stateful-promise/decorators/stateful-function';

class MyComponent extends Component {
    @statefulFunction({ throttle: true })
    async clickMe() {
        await fetch(url);
    }
}

@statefulFunction replaces @action while giving you all the features of this addon!

Stateful Promise

• Promise interface

import { StatefulPromise } from 'ember-stateful-promise/utils/stateful-promise';

const promise = fetch(url);
let result = new StatefulPromise((resolveFn, rejectFn) => {
    promise.then((data) => resolveFn(data)).catch((e) => rejectFn(e));
});

result.isRunning; // true
result.isResolved; // false
result.isError; // false

await result;

result.isRunning; // false
result.isResolved; // true
result.isError; // false

• create method with destroyable

import { StatefulPromise } from 'ember-stateful-promise/utils/stateful-promise';

const promise = fetch(url);
let result = new StatefulPromise().create(this, promise);

result.isRunning; // true
result.isResolved; // false
result.isError; // false

await result;

result.isRunning; // false
result.isResolved; // true
result.isError; // false

import { StatefulPromise } from 'ember-stateful-promise/utils/stateful-promise';
import { action } from '@ember/object';

class MyComponent extends Component {
    @action
    clickMe() {
        const promise = fetch(url);
        // Destroyable registered
        let result = new StatefulPromise().create(this, (resolveFn, rejectFn) => {
            promise.then((data) => resolveFn(data)).catch((e) => rejectFn(e));
        });

        // Component destroyed
        // and then
        try {
            await result;
        } catch (e) {
            // WILL ERROR here!
        }

    }
}

Compatibility

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

Installation

ember install ember-stateful-promise

Contributing

See the Contributing guide for details.

License

This project is licensed under the MIT License.