Ruby on rails 如何引用嵌套Rails表单中的现有模型实例？

我正在尝试构建一个配方管理员应用程序，其中包含三个主要模型：

配方-特定菜肴的配方
成分-成分列表，经唯一性验证
数量-成分和配方之间的联接表，也反映了特定配方所需的特定成分的数量。

我正在使用一个嵌套表单（见下文），我在嵌套表单（，）上使用一个很棒的Railscast构建了该表单，以获得灵感。（由于此特定模式的需要，我的表单在某些方面比教程更复杂，但我能够以类似的方式使其工作。）

但是，在提交我的表格时，将重新创建列出的任何和所有成分，如果该成分已存在于DB中，则无法通过唯一性验证并阻止创建配方。总阻力

因此，我的问题是：是否有一种方法可以提交此表单，以便如果存在名称与我的一个配料名称字段匹配的配料，它将引用现有配料，而不是尝试创建具有相同名称的新配料

代码细节如下

---

在

Recipe.rb

中：

class Recipe < ActiveRecord::Base
  attr_accessible :name, :description, :directions, :quantities_attributes,
                  :ingredient_attributes

  has_many :quantities, dependent: :destroy
  has_many :ingredients, through: :quantities
  accepts_nested_attributes_for :quantities, allow_destroy: true

class Quantity < ActiveRecord::Base
  attr_accessible :recipe_id, :ingredient_id, :amount, :ingredient_attributes

  belongs_to :recipe
  belongs_to :ingredient
  accepts_nested_attributes_for :ingredient

class Ingredient < ActiveRecord::Base
  attr_accessible :name
  validates :name, :uniqueness => { :case_sensitive => false }

  has_many :quantities
  has_many :recipes, through: :quantities

class Ingredient < ActiveRecord::Base
  before_save { self.name.downcase! } # to simplify search and unified view
  validates :name, :uniqueness => { :case_sensitive => false }

  has_many :quantities
  has_many :recipes, through: :quantities
end

def new
  @recipe = Recipe.new
  3.times do
    @recipe.quantities.build #initialize recipe -> quantities association
    @recipe.quantities.last.build_ingredient #initialize quantities -> ingredient association
  end
end

def create
  @recipe = Recipe.new(recipe_params)    
  prepare_recipe

  if @recipe.save ... #now all saved in proper way
end

def update
  @recipe = Recipe.find(params[:id])
  @recipe.attributes = recipe_params
  prepare_recipe    

  if @recipe.save ... #now all saved in proper way
end

private 
def prepare_recipe
  @recipe.quantities.each do |quantity|
    # do case-insensitive search via 'where' and building SQL-request
    if ingredient = Ingredient.where('LOWER(name) = ?', quantity.ingredient.name.downcase).first
      quantity.ingredient_id = quantity.ingredient.id = ingredient.id
    end
  end
end

def recipe_params
  params.require(:recipe).permit(
    :name,
    :description,
    :directions,
    :quantities_attributes => [
      :id,
      :amount,
      :_destroy,
      :ingredient_attributes => [
        #:id commented bc we pick 'id' for existing ingredients manually and for new we create it
        :name
  ]])
end

在

配料.rb

中：

class Recipe < ActiveRecord::Base
  attr_accessible :name, :description, :directions, :quantities_attributes,
                  :ingredient_attributes

  has_many :quantities, dependent: :destroy
  has_many :ingredients, through: :quantities
  accepts_nested_attributes_for :quantities, allow_destroy: true

class Quantity < ActiveRecord::Base
  attr_accessible :recipe_id, :ingredient_id, :amount, :ingredient_attributes

  belongs_to :recipe
  belongs_to :ingredient
  accepts_nested_attributes_for :ingredient

class Ingredient < ActiveRecord::Base
  attr_accessible :name
  validates :name, :uniqueness => { :case_sensitive => false }

  has_many :quantities
  has_many :recipes, through: :quantities

class Ingredient < ActiveRecord::Base
  before_save { self.name.downcase! } # to simplify search and unified view
  validates :name, :uniqueness => { :case_sensitive => false }

  has_many :quantities
  has_many :recipes, through: :quantities
end

def new
  @recipe = Recipe.new
  3.times do
    @recipe.quantities.build #initialize recipe -> quantities association
    @recipe.quantities.last.build_ingredient #initialize quantities -> ingredient association
  end
end

def create
  @recipe = Recipe.new(recipe_params)    
  prepare_recipe

  if @recipe.save ... #now all saved in proper way
end

def update
  @recipe = Recipe.find(params[:id])
  @recipe.attributes = recipe_params
  prepare_recipe    

  if @recipe.save ... #now all saved in proper way
end

private 
def prepare_recipe
  @recipe.quantities.each do |quantity|
    # do case-insensitive search via 'where' and building SQL-request
    if ingredient = Ingredient.where('LOWER(name) = ?', quantity.ingredient.name.downcase).first
      quantity.ingredient_id = quantity.ingredient.id = ingredient.id
    end
  end
end

def recipe_params
  params.require(:recipe).permit(
    :name,
    :description,
    :directions,
    :quantities_attributes => [
      :id,
      :amount,
      :_destroy,
      :ingredient_attributes => [
        #:id commented bc we pick 'id' for existing ingredients manually and for new we create it
        :name
  ]])
end

link_to

和

link_to_功能

允许动态添加和删除数量/成分对，并根据前面提到的Railscast进行了修改。他们可以使用一些重构，但或多或少都应该这样做

---

更新：根据Leger的请求，以下是来自

recipes\u controller.rb

的相关代码。在

Recipes#new

路线中，

3.times{@recipe.quantities.build}

为任何给定配方设置三个空白数量/成分对；可以使用上面提到的“添加成分”和“删除”链接动态删除或添加这些内容

class RecipesController < ApplicationController

  def new
    @recipe = Recipe.new
    3.times { @recipe.quantities.build }
    @quantity = Quantity.new
  end

  def create
    @recipe = Recipe.new(params[:recipe])

    if @recipe.save
      redirect_to @recipe
    else
      render :action => 'new'
    end
  end

class RecipesController“新建”
结束
结束

你不应该把成分匹配的逻辑放在眼里-在将它们传递给模型之前，创建合适的对象是

配方#的职责。请分享控制器的相关代码

在开始编写代码之前，请注意以下几点：

我用Rails4@ruby2.0，但尝试编写与Rails3兼容的代码
attr\u acessible
在Rails 4中被弃用，因此改用强参数。如果你想升级你的应用程序，从一开始就使用强大的参数
建议将
成分
制成低外壳，以便在外壳不敏感的情况下提供均匀的外观
好了，我们开始：

删除
Recipe.rb
、
Quantity.rb
和
component.rb
中的
attr\u accessible
字符串

不区分大小写，小写
component.rb
：

class Recipe < ActiveRecord::Base
  attr_accessible :name, :description, :directions, :quantities_attributes,
                  :ingredient_attributes

  has_many :quantities, dependent: :destroy
  has_many :ingredients, through: :quantities
  accepts_nested_attributes_for :quantities, allow_destroy: true

class Quantity < ActiveRecord::Base
  attr_accessible :recipe_id, :ingredient_id, :amount, :ingredient_attributes

  belongs_to :recipe
  belongs_to :ingredient
  accepts_nested_attributes_for :ingredient

class Ingredient < ActiveRecord::Base
  attr_accessible :name
  validates :name, :uniqueness => { :case_sensitive => false }

  has_many :quantities
  has_many :recipes, through: :quantities

class Ingredient < ActiveRecord::Base
  before_save { self.name.downcase! } # to simplify search and unified view
  validates :name, :uniqueness => { :case_sensitive => false }

  has_many :quantities
  has_many :recipes, through: :quantities
end

def new
  @recipe = Recipe.new
  3.times do
    @recipe.quantities.build #initialize recipe -> quantities association
    @recipe.quantities.last.build_ingredient #initialize quantities -> ingredient association
  end
end

def create
  @recipe = Recipe.new(recipe_params)    
  prepare_recipe

  if @recipe.save ... #now all saved in proper way
end

def update
  @recipe = Recipe.find(params[:id])
  @recipe.attributes = recipe_params
  prepare_recipe    

  if @recipe.save ... #now all saved in proper way
end

private 
def prepare_recipe
  @recipe.quantities.each do |quantity|
    # do case-insensitive search via 'where' and building SQL-request
    if ingredient = Ingredient.where('LOWER(name) = ?', quantity.ingredient.name.downcase).first
      quantity.ingredient_id = quantity.ingredient.id = ingredient.id
    end
  end
end

def recipe_params
  params.require(:recipe).permit(
    :name,
    :description,
    :directions,
    :quantities_attributes => [
      :id,
      :amount,
      :_destroy,
      :ingredient_attributes => [
        #:id commented bc we pick 'id' for existing ingredients manually and for new we create it
        :name
  ]])
end

在
prepare_recipe
中，我们执行以下操作：

查找具有给定名称的配料ID
将外键
数量。成分id
设置为id
将
quantity.component.id
设置为id（想想如果不这样做会发生什么，并更改配方中的配料名称）
享受吧
 感谢您的回复——我已经在我的原始帖子底部添加了相关的控制器代码。注意，关于视图中的逻辑，但我不确定哪一行是令人不快的。我想确保用户在创建配方时可以添加配料及其数量，我试图将代码限制为表单所需的内容。更新配方时如何填充配料字段？上面的代码片段似乎不起作用。（Rails 4.1.4）另外，如何查询数量？有没有办法将其映射到配料？i、 e.@recipe.component[1]。数量？非常感谢您的回答。我能使它适应我的申请。