ember-data-cascade-delete  

Sometimes we have a "Composition" kind of relationship (per UML terms) where the lifecyle of one
class is closely related to another.

Composition relationships represents a "part-whole" relationship such that class B is an integral part of class A.
This relationship is typically used if objects of class A can't logically exist without having a class B object.

E.g, if a Human model "has many" Legs, we want to destroy the legs if/when the Human is destroyed.

For such cases, we need to "cascade delete" the related models along with the parent model.
This addon provides a Mixin with this functionality for you to add to any adapter in your ember app.

Installation

Just run

``bash
ember install ember-data-cascade-delete
`

Usage

If we want to add this feature globally, we add the Mixin to the application adapter:

`js
// app/adapters/application.js
import JSONAPIAdapter from '@ember-data/adapter/json-api';
import CascadeDeleteMixin from 'ember-data-cascade-delete';

export default class ApplicationAdapter extends JSONAPIAdapter.extend(CascadeDeleteMixin) {
}
`

You can also add this mixin to any other more specific (model-scoped) adapter.

Now we can specify a cascadeDelete option in our relationships like:

`js
// app/models/human.js
import Model, { attr, belongsTo, hasMany } from '@ember-data/model';

export default class Human extends Model {
@attr('string')
name;

@belongsTo('heart', { async: true, inverse: 'human', cascadeDelete: true })
heart;

@hasMany('leg', { async: true, inverse: 'human', cascadeDelete: true })
legs;
}
`

Now when we call human.destroyRecord() the related records marked with cascadeDelete: true
will be unloaded after the main record is destroyed.

Two things to note:
- this will work with nested relationships, e.g a Leg could have a hasMany relationship to Finger and
those would also be unloaded.
- beware of circular relationships. If you define cascadeDelete: true on both ends of a relationship, you will get infinite loops.

Credits

This addon is essentially the addonified version of this blog post, with
the additional feature of nested cascade delete relationships.

Running

* ember serve
* Visit your app at http://localhost:4200.

Running Tests

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

Building

* ember build`

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