Loopback cascade mixin gist

cascade.js

/* jshint node:true */
'use strict';

/**
 * There is an incubating feature to cascade the deletes to the relational tables. see
 * https://github.com/strongloop/loopback-datasource-juggler/issues/88
 */
var lazy = require('lazy.js');
var async = require('async');
var log = require('debug')('mixins:cascade');
var Q = require('q');

module.exports = function (Model, options) {
    var matchRelation = function (name) {
        return lazy(Model.relations).find(function (mr) {
            return mr.name === name;
        });
    };

    //Pre-process and remove unsupported relations
    lazy(options).keys().forEach(function (relationName) {
        var relation = matchRelation(relationName);
        if (relation && relation.type === 'referencesMany') {
            log("Cascading to referencesMany is not supported - %s", relation.name);
            delete options[relationName];
        }
    });

    Model.observe('after delete', function (ctx, next) {
        if (!(ctx.instance || ctx.where)) {
            log("There is no way to apply cascading deletes on a multi-record delete");
            return; //Nothing we can do
        }
        var thisId = ctx.instance ? ctx.instance.id : ctx.where.id;
        lazy(options).keys().each(function (relationName) {
            var relation = matchRelation(relationName);
            if (!relation) {
                return;
            }
            var filter = {};
            filter[relation.keyTo] = thisId;
            if (options[relationName].unlink) {
                var throughModel = relation.modelThrough;
                if (throughModel) {
                    breakLinks(throughModel, filter, next);
                } else {
                    log("%s.%s does not have a through model. Nothing to unlink", Model.definition.name, relationName);
                }
            } else {
                //See https://gist.github.com/fabien/126ccfaca48ddf1cefb8
                relation.modelTo.find({where: filter}).then(function (items) {
                    Q.all(
                        lazy(items).map(function (inst) {
                            return inst.destroy();
                        }).toArray()
                    ).then(function (results) {
                            log("Cascaded delete of: ", results);
                            if (relation.modelThrough) {
                                breakLinks(relation.modelThrough, filter, next);
                            } else {
                                next();
                            }
                        }).catch(function (err) {
                            next(err);
                        });
                });
            }
        });
    });

    function breakLinks(throughModel, filter, next) {
        throughModel.destroyAll(filter).then(function (info) {
            log("Removed %d links from %s referring to %s", info.count, throughModel.definition.name, Model.definition.name);
            next();
        }).catch(function (err) {
            next(err);
        });
    }

};