Delete associated model with ember-data - ember.js

Question

I have two models:
App.User = DS.Model.create({
comments: DS.hasMany('App.Comment')
});
App.Comment = DS.Model.create({
user: DS.belongsTo('App.User')
});
When a user is deleted, it also will delete all its comments on the backend, so I should delete them from the client-side identity map.
I'm listing all the comments on the system from another place, so after deleting a user it would just crash.
Is there any way to specify this kind of dependency on the association? Thanks!

Answer 1

I use a mixin when I want to implement this behaviour. My models are defined as follows:
App.Post = DS.Model.extend(App.DeletesDependentRelationships, {
dependentRelationships: ['comments'],
comments: DS.hasMany('App.Comment'),
author: DS.belongsTo('App.User')
});
App.User = DS.Model.extend();
App.Comment = DS.Model.extend({
post: DS.belongsTo('App.Post')
});
The mixin itself:
App.DeletesDependentRelationships = Ember.Mixin.create({
// an array of relationship names to delete
dependentRelationships: null,
// set to 'delete' or 'unload' depending on whether or not you want
// to actually send the deletions to the server
deleteMethod: 'unload',
deleteRecord: function() {
var transaction = this.get('store').transaction();
transaction.add(this);
this.deleteDependentRelationships(transaction);
this._super();
},
deleteDependentRelationships: function(transaction) {
var self = this;
var klass = Ember.get(this.constructor.toString());
var fields = Ember.get(klass, 'fields');
this.get('dependentRelationships').forEach(function(name) {
var relationshipType = fields.get(name);
switch(relationshipType) {
case 'belongsTo': return self.deleteBelongsToRelationship(name, transaction);
case 'hasMany': return self.deleteHasManyRelationship(name, transaction);
}
});
},
deleteBelongsToRelationship: function(name, transaction) {
var record = this.get(name);
if (record) this.deleteOrUnloadRecord(record, transaction);
},
deleteHasManyRelationship: function(key, transaction) {
var self = this;
// deleting from a RecordArray doesn't play well with forEach,
// so convert to a normal array first
this.get(key).toArray().forEach(function(record) {
self.deleteOrUnloadRecord(record, transaction);
});
},
deleteOrUnloadRecord: function(record, transaction) {
var deleteMethod = this.get('deleteMethod');
if (deleteMethod === 'delete') {
transaction.add(record);
record.deleteRecord();
}
else if (deleteMethod === 'unload') {
var store = this.get('store');
store.unloadRecord(record);
}
}
});
Note that you can specify via deleteMethod whether or not you want to send the DELETE requests to your API. If your back-end is configured to delete dependent records automatically, then you will want to use the default.
Here's a jsfiddle that shows it in action.

Answer 2

A quick-and-dirty way would be to add the following to your user model
destroyRecord: ->
#get('comments').invoke('unloadRecord')
#_super()

Answer 3

I adapted the answer of #ahmacleod to work with ember-cli 2.13.1 and ember-data 2.13.0. I had an issue with nested relationships and the fact that after deleting an entity from the database its id was reused. This lead to conflicts with remnants in the ember-data model.
import Ember from 'ember';
export default Ember.Mixin.create({
dependentRelationships: null,
destroyRecord: function() {
this.deleteDependentRelationships();
return this._super()
.then(function (model) {
model.unloadRecord();
return model;
});
},
unloadRecord: function() {
this.deleteDependentRelationships();
this._super();
},
deleteDependentRelationships: function() {
var self = this;
var fields = Ember.get(this.constructor, 'fields');
this.get('dependentRelationships').forEach(function(name) {
self.deleteRelationship(name);
});
},
deleteRelationship (name) {
var self = this;
self.get(name).then(function (records) {
if (!records) {
return;
}
var reset = [];
if (!Ember.isArray(records)) {
records = [records];
reset = null;
}
records.forEach(function(record) {
if (record) {
record.unloadRecord();
}
});
self.set(name, reset);
});
},
});
Eventually, I had to set the relationship to [] (hasMany) or null (belongsTo). Else I would have run into the following error message:
Assertion Failed: You cannot update the id index of an InternalModel once set. Attempted to update <id>.
Maybe this is helpful for somebody else.