Delete associated model with ember-data

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!

score 9 · Accepted Answer · answered Mar 03 '13 at 03:10

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.

Hey, this looks extremely OK! Although I think `ember-data` should support something like that in core. Thanks for such a detailed explanation, dude! — josepjaume, Mar 03 '13 at 11:00
I agree. Ember Data is missing some key features but it's still very young and improving very quickly. — ahmacleod, Mar 03 '13 at 17:40
Ember Data no longer supports transactions, so the code above will need to be modified to work with recent builds. — ahmacleod, Sep 11 '13 at 19:20

andorov · Answer 2 · 2014-11-04T21:08:05.270

3

A quick-and-dirty way would be to add the following to your user model

destroyRecord: ->
  @get('comments').invoke('unloadRecord')
  @_super()

edited Nov 04 '14 at 21:08

answered Oct 29 '14 at 21:39

andorov

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score 0 · Answer 3 · answered Jun 04 '17 at 08:32

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.

Delete associated model with ember-data

3 Answers3

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