尝试以多对多关系创建一个实例和多个相关实例 [英] Trying to create an instance and multiple related instances in a many to many relationship

问题描述

我试图使用联结表创建一个具有多对多关系的实例和多个相关实例。

I am attempting to create an instance and multiple related instances with a many to many relation using a junction table.

在创建多个相关实例时，我需要也向联结表上的属性添加值。我不知道是不是我缺乏对续篇或诺言的知识导致了我的问题。

While creating the multiple related instances, I need to add a value to a property on the junction table as well. I don't know if it is my lack of knowledge of sequelize or promises that is causing my problem.

我正在使用的代码如下。这段代码确实将项目添加到数据库中，但是在操作完成后，我需要重定向，这是行不通的。

The code I am using is below. This code does add the items to the database, but I need to redirect after the operation has completed, which is not working.

基本上，我需要创建一个配方。创建完成后，我需要创建成分并将它们与该配方相关联。成分存储在HTML页面上来自表单的数组中。在关联成分时，我需要将 recipient_quantity添加到RecipeIngredients表中，该表是关系的贯穿部分（连接表）。

Basically, I need to create a Recipe. Once that is created, I need to create Ingredients and relate them to that Recipe. The ingredients are stored in an array coming from a form on an HTML page. While relating the Ingredients, I need to add the ingredient_quantity to the RecipeIngredients table, which is the through part of the relationship (the junction table).

global.db.Recipe.belongsToMany(
    global.db.Ingredient, 
    { 
        as: 'Ingredients', 
        through: global.db.RecipeIngredients, 
        foreignKey: 'recipe_id' 
    });
global.db.Ingredient.belongsToMany(
    global.db.Recipe, 
    { 
        as: 'Recipes', 
        through: global.db.RecipeIngredients, 
        foreignKey: 'ingredient_id' 
    });

router.post('/new', ensureLoggedIn, bodyParser.json(), function (req, res) {
    var recipeName = req.body.recipe_name;
    var steps = req.body.steps;
    var ingredients = req.body.ingredients;
    var ingredientQty = {};
    var currentIngredient;
    var ingredientsToAdd = [];

    db.Recipe.create({
        recipe_name: recipeName,
        directions: steps,
        FamilyId: req.user.FamilyId,
        CreatedBy: req.user._id
    })
    .then(function (recipe) {
        for (var i = 0; i < ingredients.length; i++) {

            currentIngredient = ingredients[i];
            ingredientQty[currentIngredient.ingredient_name] = 
currentIngredient.quantity;

            db.Ingredient.findOrCreate({
                where: { 
                    ingredient_name: currentIngredient.ingredient_name, 
                    FamilyId: req.user.FamilyId 
                }
            })
            .spread(function (ingredient, created) {
                if (created) {
                    console.log("Added Ingredient to DB: " + 
                    currentIngredient.ingredient_name);
                }

            ingredient.Recipes = {
                ingredient_quantity: 
                    ingredientQty[ingredient.ingredient_name]
            };
            ingredient.CreatedBy = req.user._id;
            recipe.addIngredient(ingredient)
            .then(function () {
                console.log("Added Ingredient " + ingredient.ingredient_name 
                + " to Recipe " + recipe.recipe_name);
            });
        })
    }

})
.finally(function(recipe){
    res.redirect('/recipes');
});
});

任何帮助将不胜感激。我知道我因为尝试在循环中使用Promise而遇到问题，我只是不知道我还能怎么做到这一点。

Any help would be greatly appreciated. I know that I am running into issues because of trying to use promises inside of a loop, I just don't know how else I can accomplish this.

推荐答案

我能够解决自己遇到的问题。答案此处有助于我提出我的解决方案。
如果有人遇到类似问题，我将在下面发布解决方案。我创建了一个变量来存储来自Recipe.create（）的Promise，我使用Promise.map从表单数据中查找或创建所有成分。因为 findOrCreate 返回包含以下内容的数组Promise和一个布尔值（如果已创建该项目），然后我必须从Promise.map函数的结果中获取实际成分。因此，我使用了JavaScript array.map（）函数来从数组中获取第一项。最后，再次使用Promise.map将每种成分添加到配方中

I was able to fix the problem that I was having. The answers here helped me come up with my solution. I am posting the solution below in case anyone else runs into a similar issue. I created a variable to store the Promise from Recipe.create(), I used Promise.map to findOrCreate all of the ingredients from the form data. Because findOrCreate returns an array containing Promise and a boolean for if the item was created, I then had to get the actual ingredients out of the results of the Promise.map function. So I used the JavaScript array.map() function to get the first item from the arrays. And finally, use Promise.map again to add each Ingredient to the Recipe

var ingredients = req.body.ingredients,
    recipeName = req.body.recipeName,
    ingredientsQty = {}; // Used to map the ingredient and quantity for the 
                         // relationship, because of the Junction Table

var recipe = models.Recipe.create({recipe_name: recipeName});

// Use Promise.map to findOrCreate all ingredients from the form data
Promise.map(ingredients, function(ing){
    ingredientsQty[ing.ingredient_name] = ing.ingredient_quantity;
    return models.Ingredient.findOrCreate({ where: { ingredient_name: ing.ingredient_name}});
})

// Use JavaScript's Array.prototype.map function to return the ingredient 
// instance from the array returned by findOrCreate
.then(function(results){
    return results.map(function(result){
        return result[0];
    });
})

// Return the promises for the new Recipe and Ingredients
.then(function(ingredientsInDB){
    return Promise.all([recipe, ingredientsInDB]);
})

// Now I can use Promise.map again to create the relationship between the / 
// Recipe and each Ingredient
.spread(function(addedRecipe, ingredientsToAdd){
    recipe = addedRecipe;
    return Promise.map(ingredientsToAdd, function(ingredientToAdd){
        ingredientToAdd.RecipeIngredients = {
            ingredient_quantity: ingredientsQty[ingredientToAdd.ingredient_name]
        };

        return recipe.addIngredient(ingredientToAdd);
    });
})

// And here, everything is finished
.then(function(recipeWithIngredients){
   res.end
});

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