Rails 4:使用具有has_many通过关系的嵌套形式保存子记录ID，但不保存其属性 [英] Rails 4: child record ID is saved but not its attributes, using nested form with has_many through relationship
问题描述
我有3个通过关系具有has_many的模型:食物(例如巧克力)，Sub(巧克力食物替代品)，关节(关节表).
I have 3 models with a has_many through relationship: Food (eg: Chocolate), Sub (Chocolate food substitute), Joint (joint table).
说@food = Food.find(1); has_many通过关系允许我执行@subs = @ food.subs，该操作返回与@food相关的所有替代项.可以正常工作，但是只保存Sub id，而不保存它的:name和:description属性，因为您尝试在控制器中的create动作中保存@ food.subs时会返回nil
Say @food = Food.find(1); The has_many through relationship allows me to do @subs = @food.subs which return all substitutes associated with @food. This work fine, however only the Sub id is saved and not its attributes which are :name and :description as you can see it returned nil when trying to save @food.subs in my create action in my controller:
=> #<ActiveRecord::Associations::CollectionProxy [#<Sub id: 28,name:nil,description:nil,created_at:
"2015-01-07 00:40:35", updated_at: "2015-01-07 00:40:35">]>
我想问题出在我的食品控制器中的create动作，也可能与嵌套表格有关.我花了无数小时试图找出答案，我非常渴望找到答案.我真的不知道在哪里看了. 我是Rails的新手，非常感谢您的帮助和您的宝贵时间，我真的很感激.请尽可能将您的答案调整为我的初学者级别:-).
I guess the issue lies with my create action in my food controller and perhaps something to do with my nested form as well. I spent countless hours trying to figure this out I am so desperate to find an answer. I really do not know where to look anymore. I am new to rails so thanks a lot for your help and your time, I really appreciate it. Please if possible adapt your answer to my beginner level :-) .
下面是我的控制器，表格和相关信息的示例.
Down below are samples of my controller, form and relevant information.
这是我的模特:
class Food < ActiveRecord::Base
has_many :joints
has_many :subs, :through => :joints
accepts_nested_attributes_for :subs
end
class Sub < ActiveRecord::Base
has_many :joints
has_many :foods, :through => :joints
accepts_nested_attributes_for :foods
end
class Joint < ActiveRecord::Base
belongs_to :food
belongs_to :sub
end
这是我的数据库模式供参考:
Here is my db-schema FYI:
create_table "foods", force: true do |t|
t.string "name"
t.text "description"
t.datetime "created_at", null: false
t.datetime "updated_at", null: false
end
create_table "joints", force: true do |t|
t.integer "food_id"
t.integer "sub_id"
t.datetime "created_at", null: false
t.datetime "updated_at", null: false
end
create_table "subs", force: true do |t|
t.string "name"
t.text "description"
t.datetime "created_at", null: false
t.datetime "updated_at", null: false
end
这是我的foods_controller:
Here is my foods_controller:
def new
@food = Food.new
@sub = Sub.new
end
def create
@food = Food.new(food_params)
@food.subs.build(params[:subs])
@food.save
respond_to do |format|
if @food.save
format.html { redirect_to @food, notice: 'Food was successfully created.' }
format.json { render :show, status: :created, location: @food }
else
format.html { render :new }
format.json { render json: @food.errors, status: :unprocessable_entity }
end
end
end
private
def food_params
params.require(:food).permit(:name, :description, subs_attributes: [:name, :description])
end
end
这是我的意见/食物/表格:
Here is my views/foods/_form:
<%= form_for(@food) do |f| %>
<% if @food.errors.any? %>
<div id="error_explanation">
<h2><%= pluralize(@food.errors.count, "error") %> prohibited this food from being saved:</h2>
<ul>
<% @food.errors.full_messages.each do |message| %>
<li><%= message %></li>
<% end %>
</ul>
</div>
<% end %>
<div class="field">
<%= f.label :name %><br>
<%= f.text_field :name %>
</div>
<div class="field">
<%= f.label :description %><br>
<%= f.text_area :description %>
</div>
<div>
<%= f.fields_for(@sub) do |sub| %>
<div class="field">
<%= sub.label :name %>
<%= sub.text_field :name %>
</div>
<div class="field">
<%= sub.label :description %>
<%= sub.text_area :description %>
</div>
<% end %>
</div>
<div class="actions">
<%= f.submit %>
</div>
<% end %>
如果有帮助，我的路线: 资源:食品
My routes in case it helps: resources :foods
resources :subs
resources :joints
root "foods#index"
非常感谢您！
Antoine.
推荐答案
在您的新操作中:
def new
@food = Food.new
@food.subs.build
end
并在您看来:
<%= f.fields_for :subs do |sub| %>
当您直接传递一个对象时，该对象将成为新的form_builder的对象-rails不知道它以任何方式与原始对象连接，因此会导致不同的字段名称.
When you're passing directly an object, this object becomes the new form_builder's object - rails have no idea it is in any way connected with original object so it will result in different field names.
当您传递符号时，rails将首先尝试查找当前对象是否定义了subs_attributes方法.如果是这样，它将遍历subs关联并为每个关联的模型构建字段.
When you pass a symbol, rails will first try to find if your current object defines subs_attributes method. If so it will loop over subs association and build the fields for each associated model.
参考此处.
更新-评论的答案:
首先-@subs不是符号，它是一个实例变量.符号以冒号开头，例如:subs.当fields_for接收到一个参数时，它将检查它是符号还是对象.在前一种情况下，它搜索与表单生成器(f.object)关联的对象，以查明是否定义了<passed_symbol>_attributes=.这样一来，它便知道该模型接受此关联的嵌套属性，因此它可以相应地工作(为每个关联的对象使用正确的名称-<symbol>_attributes创建了新的表单生成器).
Firstly - @subs is not a symbol, it is an instance variable. Symbols start with a colon like :subs. When fields_for receives an argument, it checks whether it is a symbol or object. In former case it search an object associated with form builder (f.object) to find out if it defines <passed_symbol>_attributes=. That way it knows that the model accepts nested attributes for this association so it can behave accordingly (the new form builder is created for each associated object with a correct name - <symbol>_attributes).
传递对象时，rails无法检测它是否以某种方式连接到当前对象-您可能会为同一类型的对象建立两个关联，甚至可能与原始对象完全没有关系目的.在这种情况下，fields_for就像是嵌套的form_for一样-生成的表单生成器将携带对象的模型名称(f.object.class.model_name.singular)
When object is passed, rails has no way of detecting if this is in ay way connected to the current object - you could have two associations for the same type of objects, or even it might have absolutely nothing to do with the original object. In that case fields_for acts like it was a nested form_for - resulting form builder will carry the model name of the object (f.object.class.model_name.singular)
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