如何在Rails 5中从匹配ID的连接表中获取记录数(How to get count of records from join table with matching ID in Rails 5)

我有2个模型。膳食和食物。一顿饭可以有很多食物，一种食物可以是多餐的一部分。他们有一个多对多的关联，由has_many：through完成。连接模型称为MealFood，连接表称为meal_foods。创建膳食时，您可以添加尽可能多的食物。有一个jQuery按钮，当你点击它时会自动在窗体中添加一个新的输入，并在那里输入食物。如何使膳食的编辑视图显示与食物项目名称一样多的输入字段。

膳食控制器：

def create @meal = current_user.meals.new(meal_params) if @meal.save @meal.update(total_calories: @meal.calc_total_calories, total_carbohydrates: @meal.calc_total_carbohydrates, total_proteins: @meal.calc_total_proteins, total_fat: @meal.calc_total_fat) redirect_to @meal else render 'new' end end def edit @meal = Meal.find(params[:id]) end def update if @meal.update(meal_params) @meal.update(total_calories: @meal.calc_total_calories, total_carbohydrates: @meal.calc_total_carbohydrates, total_proteins: @meal.calc_total_proteins, total_fat: @meal.calc_total_fat) redirect_to @meal else render 'edit' end end

膳食视图（创建操作）：

<%= form_for(@meal) do |f| %> <div class="field"> <%= f.label :meal_type %> <%= f.select :meal_type, ["Breakfast", "Lunch", "Dinner", "Morning Snack", "Afternoon Snack", "Evening Snack"] %> </div> <div class="field"> <label class="input-dropdown">Food Item #1</label> <%= select_tag "meal[food_ids][]", options_from_collection_for_select(Food.all, "id", "name") %> </div> <div class="field submit"> <%= f.submit class: "button button-highlight button-block" %> </div> <% end %>

提前致谢！

I have 2 models. Meal and Food. A meal can have many food items and a food item can be a part of many meals. They have a many-to-many association, done by has_many :through. The join model is called MealFood and the join table is called meal_foods. When creating a meal you can add as many food items as you want. There's a jQuery button that when you click it automatically appends a new input in the form and you enter the food item there. How can I make the edit view for the meal to show as many input fields with the name of the food item as there really is.

Meals Controller:

def create @meal = current_user.meals.new(meal_params) if @meal.save @meal.update(total_calories: @meal.calc_total_calories, total_carbohydrates: @meal.calc_total_carbohydrates, total_proteins: @meal.calc_total_proteins, total_fat: @meal.calc_total_fat) redirect_to @meal else render 'new' end end def edit @meal = Meal.find(params[:id]) end def update if @meal.update(meal_params) @meal.update(total_calories: @meal.calc_total_calories, total_carbohydrates: @meal.calc_total_carbohydrates, total_proteins: @meal.calc_total_proteins, total_fat: @meal.calc_total_fat) redirect_to @meal else render 'edit' end end

Meals View (create action):

<%= form_for(@meal) do |f| %> <div class="field"> <%= f.label :meal_type %> <%= f.select :meal_type, ["Breakfast", "Lunch", "Dinner", "Morning Snack", "Afternoon Snack", "Evening Snack"] %> </div> <div class="field"> <label class="input-dropdown">Food Item #1</label> <%= select_tag "meal[food_ids][]", options_from_collection_for_select(Food.all, "id", "name") %> </div> <div class="field submit"> <%= f.submit class: "button button-highlight button-block" %> </div> <% end %>

Thanks in advance!

最满意答案

由于这是使用连接表，我假设你不希望用户真的能够编辑Food记录本身 - 他们应该编辑MealFood记录，对吧？

在这种情况下，您应该能够查询meal.meal_foods以获取要编辑的连接表记录。您的查询可能如下所示：

@meal_foods = @meal.meal_foods.includes(:food)

.includes(:food)会自动加载您需要的所有食物记录，防止您遇到N + 1查询问题。

然后在你看来，你可以做这样的事情：

如果您确实希望自己的用户能够修改Food记录，则可以使用相同的策略，但只需使用已创建的through关联。

Since this uses a join table, I assume you don't want users to actually be able to edit the Food record itself - they should be editing the MealFood record, right?

In that case, you should be able to query meal.meal_foods to get the join table records you want to edit. Your query might look something like this:

@meal_foods = @meal.meal_foods.includes(:food)

The .includes(:food) will auto-load all the food records you need, preventing you from having an N+1 query problem.

Then in your view, you can do something like this:

If you do want your users to be able to modify the Food records themselves, then you can use the same strategy, but just use the through association you already created.

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