Simple authorisation addon for Ember.

• v0.6.0 - support for unit testing abilities added - run ember g ember-can
• v0.5.0 - support for Ember 1.13+ using new Ember.Helper, removed injections
• v0.4.0 - stopped singularizing ability names to work with pods
• v0.3.0 - removed if-can helper, uses sub-expression instead

See UPGRADING for more details.

You want to conditionally allow creating a new blog post:

{{#if (can "write post")}}
  <button {{action "new"}}>Write Post</button>
{{else}}
  You can't write a new post
{{/if}}

We define an ability for the Post resource in /app/abilities/post.js:

import Ember from 'ember';
import { Ability } from 'ember-can';

export default Ability.extend({
  canWrite: Ember.computed('user.isAdmin', function() {
    return this.get('user.isAdmin');
  })
});

We can also re-use the same ability to check if a user has access to a route:

import Ember from 'ember';
import { CanMixin } from 'ember-can';

export default Ember.Route.extend(CanMixin, {
  beforeModel: function() {
    if (!this.can('write post')) {
      this.transitionTo('index');
    }
  }
});

Install this addon via ember-cli:

ember install ember-can

An ability class protects an individual model / resource which is available in the ability as model.

The ability checks themselves are simply standard Ember objects with computed properties:

import Ember from 'ember';
import { Ability } from 'ember-can';

export default Ability.extend({
  // only admins can write a post
  canWrite: Ember.computed('user.isAdmin', function() {
    return this.get('user.isAdmin');
  }),

  // only the person who wrote a post can edit it
  canEdit: Ember.computed('user.id', 'model.author', function() {
    return this.get('user.id') === this.get('model.author');
  })
});

The can helper is meant to be used with {{if}} and {{unless}} to protect a block.

The first parameter is a string which is used to find the ability class call the appropriate property (see Looking up abilities).

The second parameter is an optional model object which will be given to the ability to check permissions.

As activities are standard Ember objects and computed properties if anything changes then the view will automatically update accordingly.

{{#if (can "edit post" post)}}
  ...
{{else}}
  ...
{{/if}}

As it's a sub-expression, you can use it anywhere a helper can be used. For example to give a div a class based on an ability you can use an inline if:

<div class="{{if (can 'edit post' post) 'is-editable'}}">

</div>

If you need more than a single resource in an ability, you can pass them additional attributes.

You can do this in the helpers, for example this will set the model to project as usual, but also member as a bound property.

{{#if (can "remove member from project" project member=member)}}
  ...
{{/if}}

Similarly in routes you can pass additional attributes after or instead of the resource:

this.can('edit post', post, { author: bob });
this.can('write post', { project: project });

These will set author and project on the ability respectively so you can use them in the checks.

In the example above we said {{#if-can "write post"}}, how do we find the ability class & know which property to use for that?

First we chop off the last word as the resource type which is looked up via the container.

The ability file can either be looked up in the top level /app/abilities directory, or via pod structure.

Then for the ability name we remove some basic stopwords (of, for in) at the end, prepend with "can" and camelCase it all.

For example:

Current stopwords which are ignored are:

• for
• from
• in
• of
• to

How does the ability know who's logged in? This depends on how you implement it in your app!

If you're using an Ember.Service as your session, you can just inject it into the ability:

// app/abilities/foo.js
import Ember from 'ember';
import { Ability } from 'ember-can';

export default Ability.extend({
  session: Ember.inject.service()
});

If you're using ember-simple-auth, you'll probably want to inject the simple-auth-session:main session into the ability classes.

To do this, add an initializer like so:

// app/initializers/inject-session-into-abilities.js
export default {
  name: 'inject-session-into-abilities',
  initialize(app) {
    app.inject('ability', 'session', 'simple-auth-session:main');
  }
};

The ability classes will now have access to session which can then be used to check if the user is logged in etc...

In a controller or component, you may want to expose abilities as computed properties so that you can bind to them in your templates.

To do that there's a helper to lookup the ability for a resource, which you can then alias properties:

import { computed } from 'ember-can';
import Ember from 'ember';

export default Ember.Controller.extend({
  post: null, // set by the router

  // looks up the "post" ability and sets the model as the controller's "post" property
  ability: computed.ability('post'),

  // alias properties to the ability for easier access
  canEditPost: Ember.computed.reads('ability', 'canEdit')
});

computed.ability assumes that the property for the resource is the same as the ability resource. If that's not the case, include it as the second parameter.

import { computed } from 'ember-can';
import Ember from 'ember';

export default Ember.Controller.extend({
  // looks up the "post" ability and sets the model as the controller's "content" property
  ability: computed.ability('post', 'content')
});

Make sure that you've either ember install-ed this addon, or run the addon blueprint via ember g ember-can. This is an important step that teaches the test resolver how to resolve abilities from the file structure.

An ability unit test will be created each time you generate a new ability via ember g ability <name>. The package currently supports generating QUnit and Mocha style tests.

To unit test components that use the can helper, you'll need to needs the ability and helper file like this:
needs: ['helper:can', 'ability:foo']

• git clone this repository
• npm install
• bower install

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

• ember test
• ember test --server

• ember build

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