使用 accepts_nested_attributes_for 和 fields_for 创建控制器方法

Question

我正在使用 Rails 5.2.0 构建一个关于食谱的 Web 应用程序，我对控制器的 create 方法有疑问。

这是我的模型：

class Recipe < ApplicationRecord
    belongs_to :user
    has_many :quantities
    has_many :ingredients, through: :quantities

    accepts_nested_attributes_for :quantities, allow_destroy: true
end

class Quantity < ApplicationRecord    
    belongs_to :recipe
    belongs_to :ingredient
end

class Ingredient < ApplicationRecord
    has_many :quantities
    has_many :recipes, through: :quantities
end

这里是创建新食谱的视图：

<%= form_for(@recipe) do |f| %>

    <%= f.label :name, "Name" %>
    <%= f.text_field :name %>

    <%= f.label :servings, "Servings" %>
    <%= f.number_field :servings %>


    <%= f.fields_for :quantities do |quantity| %>

        <%= f.hidden_field :_destroy, class: "hidden-field-to-destroy" %>

        <%= f.label :ingredient_id, "Ingredient Name" %>
        <%= f.text_field :ingredient_id%>

        <%= f.label :amount, "Amount" %>
        <%= f.number_field :amount %>

        <%= f.label :unit, "Unit" %>
        <%= f.select(:unit, ["kg","g","l","ml"], {include_blank: true}) %>
    <% end %>

    <%= f.submit 'Add new recipe' %>

<% end %>

我可以使用 jquery 动态添加新成分，也可以以相同的形式删除它们。

控制器的update方法完美运行，但create方法不起作用：

class RecipesController < ApplicationController
    def create
        @recipe = current_user.recipes.build(recipe_params)
        if @recipe.save
            flash[:success] = "New recipe created correctly."
            redirect_to @recipe
        else
          render 'new'
        end
    end 

    def update
        @recipe = Recipe.find(params[:id])
        if @recipe.update_attributes(recipe_params)
          flash[:success] = "The recipe has been updated correctly."
          redirect_to @recipe
        else
          render 'edit'
        end
    end

    private
        def recipe_params
            params.require(:recipe).permit( :name, :servings, quantities_attributes: [:ingredient_id, :amount, :unit,:_destroy, :id, :recipe_id])
        end
end

我正在尝试 @recipe = current_user.recipes.build(recipe_params) 但我在视图中收到以下错误：

配方数量不能为空

我认为出现这种情况是因为在尝试创建关系时，需要指明recipe_id，但尚未创建食谱，无法指明id。

你能告诉我首先创建配方然后能够通过配方控制器的创建方法中的数量添加成分的正确方法是什么吗？

Answer 1

根据分享的消息，qunatity_recipes 不能为空，您还没有指定任何条件来管理它。

当前

class Recipe < ApplicationRecord
 belongs_to :user
 has_many :quantities
 has_many :ingredients, through: :quantities

 accepts_nested_attributes_for :quantities, allow_destroy: true
end

将食谱 class

的接受嵌套属性更新为 allow_nil

class Recipe < ApplicationRecord
 belongs_to :user
 has_many :quantities
 has_many :ingredients, through: :quantities

 accepts_nested_attributes_for :quantities, allow_destroy: true, allow_nil: true
end

使用 accepts_nested_attributes_for 和 fields_for 创建控制器方法

Create controller method with accepts_nested_attributes_for and fields_for

ruby-on-rails

associations

nested-attributes