ember-sweet-owner 🍬

The dependency injection in ember works through the Owner, which registers objects but also can be used for lookups. ember-sweet-owner brings a sugarized syntax for a typed readonly access on the Owner for better DX.

Installation

ember install ember-sweet-owner

Example

Say, you want to access the session service with an owner, here is how you do that:

import type SessionService from 'ember-simple-auth/services/session';

const session = owner.lookup('service:session') as SessionService;

this is quite a cryptic syntax for the lookup string and an API to remember. This is where ember-sweet-owner jumps in, to give you a friendly readonly access to the owner:

import { sweetenOwner } from 'ember-sweet-owner';

const { services } = sweetenOwner(owner);
const { session } = services;

// do sth with `session`

The sweet owner is typed (at least for services) but you can also add your own types for your own containers (see below).

Use Cases

ember-sweet-owner is best used in situations where you are not in a class that already has the owner set. Most likely in functions (eg. resources).

Here are notable projects making use of ember-sweet-owner:

• ember-command
• ember-ability

The duo of ember-command (for write operations) and ember-ability (for read operations) share the same API, thanks to ember-sweet-owner.

Example: Actions and Abilities

Let's say there is a CounterService, which you want to access from a single file component:

// app/services/counter.ts
import { tracked } from '@glimmer/tracking';
import Service from '@ember/service';

export default class CounterService extends Service {
  @tracked count = 0;

  inc = () => {
    this.count++;
  }

  dec = () => {
    this.count--;
  }
}

declare module '@ember/service' {
  export interface Registry {
    counter: CounterService;
  }
}

Accessing the service from with in a single file component:

// app/components/counter.gts
import { action } from 'ember-command';
import { ability } from 'ember-ability';
import { on } from '@ember/modifier';

const inc = action(({ services }) => () => {
  services.counter.inc();
});

const count = ability(({ services }) => () => {
  return services.counter.count;
});

const Counter = <template>
  {{count}} <button type="button" {{on "click" (inc)}}>+</button>
</template>

export { Counter };

Extending the Container Registry Types

By default services are typed, thanks to the Registry from @ember/service. In the same sense ember-sweet-owner makes use of the same mechanics. If you happen to rely on another container, for example an authenticator, that is within the authenticators/ folder, then you can declare that. Here is the example from ember-simple-auth with extended types from ember-sweet-owner:

// app/authenticators/oauth2.js
import OAuth2PasswordGrantAuthenticator from 'ember-simple-auth/authenticators/oauth2-password-grant';

export default class OAuth2Authenticator extends OAuth2PasswordGrantAuthenticator {}

declare module 'ember-sweet-owner' {
  export interface SweetOwner {
    authenticators: {
      oauth2: OAuth2Authenticator;
    }
  }
}

That's more to support some ember classic paradigms, but for most of the time, you want to access services.

Experimentation: ember-polaris-service

For services, there is experimentation coming from ember-polaris-service to spin off the traditional DI system of ember by using more verbose and explicit imports. If you play around with that and install in an app with ember-sweet-owner being present, the latter will become a hybrid to support the old and the new.

With ember-polaris-service installed, here is the same counter example again from above:

// app/services/counter.ts
import { tracked } from '@glimmer/tracking';
-import Service from '@ember/service';
+import Service from 'ember-polaris-service';

export default class CounterService extends Service {
  @tracked count = 0;

  inc = () => {
    this.count++;
  }

  dec = () => {
    this.count--;
  }
}

declare module '@ember/service' {
  export interface Registry {
    counter: CounterService;
  }
}

Accessing the service from with in a single file component:

// app/components/counter.gts
import { action } from 'ember-command';
import { ability } from 'ember-ability';
import { on } from '@ember/modifier';
+import CounterService from '../services/counter';

-const inc = action(({ services }) => () => {
+const inc = action(({ service }) => () => {
-  services.counter.inc();
+  service(CounterService).inc();
});

-const count = ability(({ services }) => () => {
+const count = ability(({ service }) => () => {
-  return services.counter.count;
+  return service(CounterService).count;
});

const Counter = <template>
  {{count}} <button type="button" {{on "click" (inc)}}>+</button>
</template>

export { Counter };

In order to receive type support, you need to add this to your registry in your types/ folder:

// types/index.d.ts

// ...

import type { ServiceFactory } from 'ember-polaris-service';

declare module 'ember-sweet-owner' {
  export interface SweetOwner {
    service<T>(factory: ServiceFactory<T>): T;
  }
}

That is the experimental support from ember-sweet-owner. Thanks to macros this support is only present if you have made ember-polaris-service a dependency - if not the code is stripped away, so you don't pay for something you don't need.