Ember Promise Helpers

Installation

ember install ember-promise-helpers

Description

When Ember's templates encounter a promise, it won't re-render it when the promise is resolved or rejected. For an example of the problem:

{{#if model.author}}
  The author is: {{model.author.name}}
{{else}}
  No author!
{{/if}}

If model.author is a promise (like a an Ember Data belongsTo relationship), the template will always contain the text: "The author is:", rather than "No author!".

Ember Promise Helpers allow you to work with Promises easily in your Ember templates, without wrapping your objects with something like Ember.PromiseProxyMixin in the Route, Controller, or Component.

Example Usage

await

{{#if (await model.author)}}
  {{get (await model.author) 'name'}}
{{else}}
  No author!
{{/if}}

The await helper also works anywhere, because it's just a Handlebars subexpression. For example, you can pass it to a another helper...

{{#each (await model.comments) as |comment|}}
  {{comment.author}} wrote {{comment.text}}
{{/each}}

Or passing it to a component:

{{twitter-timeline users=(await user.following)}}

You can supply a catch action which will be called upon promise rejection:

{{#if (await model.author catch=(action 'error'))}}
  {{get (await model.author) 'name'}}
{{else}}
  {{#if authorError}}
    Error loading the author: {{authorError}}
  {{else}}
    No author!
  {{/if}}
{{/if}}

The component, controller or route would have the action:

import Ember from 'ember';

export default Ember.Controller.extend({

  actions: {
    error(err, promise) {
      this.set('authorError', err.message);
      // it could also log, redirect, etc
    }
  }

});

is-pending

Resolves with false if the promise resolved or rejected, otherwise true until the promise resolves or rejects.

  {{#if (is-pending promise)}}
    <img src="loading.gif"/>
  {{else}}
    Loaded!
  {{/if}}

is-rejected

Resolves with false if the promise rejects or fails, false otherwise. Initial value is null until the promise is resolved.

  {{#unless (is-pending promise)}}
    {{#if (is-rejected promise)}}
      rejected! :(((
    {{/if}}
  {{/unless}}

is-fulfilled

Resolves with true if the promise resolved successfully, false otherwise. Initial value is null until the promise is resolved.

  {{#unless (is-pending promise)}}
    {{#if (is-fulfilled promise)}}
      Yay it worked!
    {{else}}
      Oh :(
    {{/if}}
  {{/unless}}

promise-rejected-reason

Gives you the error or reason as to why a promise was rejected. Null until the promise rejects or if the promise resolves. For example:

// app/controllers/index.js
import Ember from 'ember';

export default Ember.Controller.extend({
  promise: Ember.computed(function() {
    return Ember.RSVP.reject(new Error('whoops'));
  })
});

{{! app/templates/index.js }}

{{#if (is-rejected promise)}}
  The error was {{get (promise-rejected-reason promise) 'message'}}.
{{/if}}

This would render "The error was whoops."

Proposed Block Helper syntax (Not implemented!)

If you want to know when a promise becomes rejected or resolved, you can use the await-promise component, which gives you an error property if the promise becomes rejected (similar to calling .catch on a promise.). Another isFulfilled argument is passed for you to handle loading state:

{{#await-promise model.author as |author error isFulfilled|}}
  {{#if isFulfilled}}

    {{#unless error}}

      {{#if author}}
        The author is: {{author.name}}
      {{{else}}
        There is no author!
      {{/if}}

    {{else}}
      Oops! The error was {{error.message}}
    {{/unless}}

  {{else}}
    Loading...
  {{/if}}
{{/await-promise}}

Development Installation

git clone this repository
npm install
bower install

Running

ember server
Visit your app at http://localhost:4200.

Running Tests

npm test (Runs ember try:testall to test your addon against multiple Ember versions)
ember test
ember test --server

Building

ember build

For more information on using ember-cli, visit http://www.ember-cli.com/.

frank06/ember-promise-helpers