ember-contextual-services

Services, for instances.

Installation

ember install ember-contextual-services

Usage

First define an instance service for an object type, eg for an ember-data Person:

// app/contextual-services/person.js
import ContextualService from 'ember-contextual-services';
import computed from 'ember-computed';

export default ContextualService.extend({
  fullName: computed('model.firstName', 'model.lastName', function() {
    return [this.get('model.firstName'), this.get('model.lastName')].join(' ');
  })
});

Then we can inject the contextual-service service and fetch the instance service for an object using serviceFor:

// app/components/x-person/component.js
import Component from 'ember-component';
import service from 'ember-service/inject';

export default Component.extend({
  contextualService: service(),
  person: null,

  doSomething() {
    const personService = this.get('contextualService').serviceFor(this.get('person'));
    personService.get('fullName');
  }
});

As a shorthand, instead of injecting and looking up using the contextual-service we can use serviceFor which is syntactical sugar for the same:

// app/components/x-person/component.js
import Component from 'ember-component';
import { serviceFor } from 'ember-contextual-services';

export default Component.extend({
  personService: serviceFor('person'),
  person: null,

  doSomething() {
    return this.get('personService').get('fullName');
  }
});

Or in templates we can use the contextual-service helper:

{{get (contextual-service person) 'fullName'}}

For simple properties, this is a bit overkill, but where it comes into its own is in conjunction with ember-concurrency:

// app/contextual-services/person.js
import ContextualService from 'ember-contextual-services';
import { task, timeout } from 'ember-concurrency';

export default ContextualService.extend({
  debouncedSave: task(function * () {
    yield timeout(1000)
    yield this.get('model').save();
  }).restartable();
});

Contexts

serviceFor takes a 2nd parameter as a "context" so you can split out functionality for an object type across separate files.

For example serviceFor(person, 'display') will lookup the service from app/contextual-services/person/display.js instead of just app/contextual-services/person.js.

Service lookup

By default serviceFor will use the ember-data modelName in order to find the service.

You can change this by extending the service and overriding contextualServiceScope:

import ContextualServicesService from 'ember-contextual-services/services/contextual-service';
export default ContextualServicesService.extend({
  contextualServiceScope(model) {
    return 'foo';
  }
});

serviceFor uses the guid as the id so that the same service instance is returned each time for the same object.

Again this can be changed by overriding contextualServiceID, for example using the id instead:

import ContextualServicesService from 'ember-contextual-services/services/contextual-service';
export default ContextualServicesService.extend({
  contextualServiceID(model) {
    return model.get('key');
  }
});