Ember-can

Simple authorisation addon for Ember.

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Breaking Changes

See UPGRADING for more details.

Quick Example

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');
    }
  }
});

Installation

Install this addon via ember-cli:

ember install ember-can

Compatibility

Ember Version Ember Can Release
1.9.x 0.2
1.10 through 1.12 0.4
1.13 and beyond 0.5+

Abilities

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');
  })
});

Handlebars Helpers

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>

Additional attributes

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.

Looking up abilities

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:

String property resource pod
write post canWrite /abilities/post.js app/pods/post/ability.js
manage members in projects canManageMembers /abilities/projects.js app/pods/projects/ability.js
view profile for user canViewProfile /abilities/user.js app/pods/user/ability.js

Current stopwords which are ignored are:

Custom Ability Lookup

The default lookup is a bit "clever"/"cute" for some people's tastes, so you can override this if you choose.

Simply extend the default CanService in app/services/can.js and override parse.

parse takes the ability string eg "manage members in projects" and should return an object with propertyName and abilityName.

For example, to use the format "person.canEdit" instead of the default "edit person" you could do the following:

// app/services/can.js
import { CanService } from 'ember-can';

export default CanService.extend({
  parse(str) {
    const [abilityName, propertyName] = str.split('.');
    return {
      propertyName,
      abilityName
    }
  }
});

Injecting the user

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...

Controllers, components & computed properties

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')
});

Testing

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']

Development

Installation

Running

Running Tests

Building

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