如何从父模型创建子模型

Question

几天来，我一直在用 Rails 旋转可能的轮子。我正在使用三个模型：IngredientBase、Ingredient 和 IngredientList。 IngredientBase 包含一个字符串，可以是 "Chicken"、"Eggs" 或 "Bacon." 成分将有一个 Ingredient 和一个数量。 IngredientList 会有很多配料。

我希望用户能够 ingredient_lists/new 并且能够在提交 IngredientList 之前创建多个成分。如果不让用户提交多个表单，我怎么能做到这一点？

Answer 1

处理嵌套关系的最佳方式是使用accept_nested_attributes

为了更好地理解这里是 link

要在表单中管理 ui 级别表单，这里是 gem

Answer 2

关联

您正在查看的是nested models。

嵌套模型基本上允许您将属性附加到一个模型的实例；这些属性被发送到关联模型。

这是通过accepts_nested_attributes_for实现的：

#app/models/ingredient_list.rb
class IngrendientList < ActiveRecord::Base
   has_many :ingredients
   accepts_nested_attributes_for :ingredients
end

#app/models/ingredient.rb
class Ingredient < ActiveRecord::Base
   belongs_to :ingredient_list
end

因为你的模型让我很困惑，所以我给你重写了结构。我认为您对连接模型等感到困惑：

#app/models/ingredient.rb
class Ingredient < ActiveRecord::Base
   #columns id | name | weight | etc | created_at | updated_at
   has_many :recipe_ingredients
   has_many :recipes, through: :recipe_ingredients
end

#app/models/recipe_ingredient.rb
class RecipeIngredient < ActiveRecord::Base
    #columns id | recipe_id | ingredient_id | quantity | created_at | updated_at
    belongs_to :recipe
    belongs_to :ingredient
    accepts_nested_attributes_for :ingredient
end

#app/models/recipe.rb
class Recipe < ActiveRecord::Base
   #columns id | name | etc | etc | created_at | updated_at
   has_many :recipe_ingredients #-> allows extra attributes
   has_many :ingredients, through: :recipe_ingredients 
   accepts_nested_attributes_for :recipe_ingredients
end

这将使您能够创建 Recipe、添加新的 Ingredient，并通常使您的模型更加稳健。

以下是如何让它与控制器和视图等一起工作：

#app/controllers/recipes_controller.rb
class RecipesController < ApplicationController
   def new
      @recipe = Recipe.new
   end
   def create
      @recipe = Recipe.new recipe_params
      @recipe.save
   end

   private

   def recipe_params
      params.require(:recipe).permit(:recipe, :params, recipe_ingredients_attributes: [:quantity, ingredient_attributes:[:name]])
   end
end

这将创建一个基本表单，但我们需要包括相关字段。有几种方法可以做到这一点，包括 RailsCasts and using Cocoon.

中的 "manual" 方法

因此需要注意的重要事项是：

Every time you call a nested form field, you're basically getting Rails to add another instance of f.fields_for to your form. The VITAL thing to note here is you need to have the child_index of the fields_for block. This is what Rails uses to identify the fields, and needs to be kept unique.

您可以在 an answer I wrote some time back 上看到更多相关信息。

对于您的表单，您需要以下内容：

#app/views/recipes/new.html.erb
<%= form_for @recipe do |f| %>
   <%= f.text_field :title %> 
   <%= render "ingredients", locals: {f: f, child_index: Time.now.to_i}  %>
   <%= link_to "Add Ingredient", recipes_add_field_path, class: "ingredient" %>
   <%= f.submit %>
<% end %>

#app/views/recipes/_ingredients.html.erb
<%= f.fields_for :recipe_ingredients, child_index: child_index do |ri| %>
    <%= ri.text_field :quantity %>
    <%= ri.fields_for :ingredient do |ingredient| %>
       <%= ingredient.text_field :name %>
       <%= ingredient.text_field :weight %>
    <% end %>
<% end %>

#config/routes.rb
resources :recipes do
   member "add_field", to: "recipes#add_field"
end

#app/controllers/recipes_controller.rb
class RecipesController < ApplicationController
   def add_field
      @recipe = Recipe.new
      @recipe.recipe_ingredients.build.build_ingredient
      render "new"
   end
end

#app/assets/javascripts/application.js
$(document).on("click", "a.ingredient", function(){
   $.ajax({
      url: '/recipes/add_field',
      success: function(data){
        el_to_add = $(data).html();
        $('#recipes').append(el_to_add);
      }
      error: function(data){
         alert("Sorry, There Was An Error!");
      }
   });
});

如何从父模型创建子模型

How to create a child model from a parent

controller

nested

model

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