Get list of objects not yet in a relation in Parse.com Angular javascript

Question

I am building an AngularJS CRUD site to add data to Parse.com to be used by mobile apps that will read it. (The CRUD is easier to do on a real keyboard due to the amount of data added.) First step is to create and save the Child objects (Ingredients and Steps), and then to create and save a Recipe object that has a Relation to the Ingredients and Steps. I need to use Relation and not Pointers for these. (because I may need this to be many to many in future)

Here's my problem: writing the query to find any Ingredients and Steps that were created that are NOT yet part of a relation, to find the ones to be added to a new recipe.

The examples in the Javascript SDK don't show this scenario, they only show a query for a relation that exists, but does not have an additional attribute on the related item (comments for posts where post doesn't have an image).

Recipe has ingredients, a Relation<Ingredient>, and steps, a Relation<Step>.

This doesn't work to get the Ingredients that are not yet related to a Recipe.

    var Recipe = Parse.Object.extend("Recipe");
    var Ingr = Parse.Object.extend("Ingredient");

    recipeQuery= new Parse.Query(Recipe);
    recipeQuery.exists("ingredients");

    query = new Parse.Query(Ingr);
    query.doesNotMatchQuery("recipe",recipeQuery);
    query.ascending('name');
    query.find({
        success: function (data) {
            if (data.length > 0) {
                $scope.loadingMsg = '';
            }
            $scope.ingredients = data;
        }
    });

Answer 1

angular
.module('app.services')
.service('siteService', function($q, ParseService, $timeout) {
    var that = this;
    this.fetchIngr = function() {
        return this.fetchRecipes().then(function(recipes) {
            var q = recipes.reduce(function(initial, current) {
                initial.push(that.fetchIngredient(current));
                return initial;
            }, []);
            return $q.all(q);
        });
    };

    this.fetchRecipes = function() {
        var defer = $q.defer();
        var Recipe = Parse.Object.extend("Recipe");
        recipeQuery = new Parse.Query(Recipe);
        recipeQuery.ascending('name');
        recipeQuery.find({
            success: function(data) {
                console.log('data', data)
                defer.resolve(data);
            },
            error: function(error) {
                defer.reject(error);
            }
        });
        return defer.promise;

    };
    this.fetchIngredient = function(recipe) {
        var defer = $q.defer();
        recipe.relation('ingredients').query().find({
            success: function(res) {
                defer.resolve(res);
            },
            error: function(error) {
                defer.reject(error);
            }
        });
        return defer.promise;
    };

})

Usage:

 siteService.fetchIngr().then(function(all){
            console.log('flatten all ingr for used recipes',[].concat.apply([], all));
        });

in the fetchIngr function you will receive array of all ingredients that are used in the Recipe. then you have to the diff between two arrays to find not used ingredients. To do the subtract you should fetch all ingredients and to make subtraction between two arrays (one used ingrdients for recipes and the one with all ingredients). see here the post : JavaScript array difference

if you have questions feel free to ask me.