如何为 has_one 关联创建视图? [英] How do I create the view for the has_one association?

问题描述

所以，假设我有这个模型:

So, imagine I have this model:

class Car
  has_one :engine
end

和引擎型号:

class Engine
  belongs_to :car
end

当我向用户展示表单，以便他可以创建一辆新车时，我只想让他从可用引擎中选择一个(可用引擎将在 select，由 collection_select 填充).问题是，如果我像这样构建字段:

When I present the form for the user, so that he can create a new car, I only want to allow him to select from one of the available engines ( the available engines will be in a select, populated by the collection_select ). The thing is, if I build the field like this:

<%= f.collection_select :engine,Engine.all,:id,:name %>

当我尝试保存它时，我会得到一个 AssociationTypeMismatch，说它需要一个引擎，但它收到了一个字符串.

When I will try to save it, I will get an AssociationTypeMismatch saying that it expected an Engine, but it received a string.

这是这样做的方式吗?

def create
  car = Car.new(params[:car])
  engine = Engine.find(params[:engine])
  car.engine = engine
  if car.save
     # redirect somewhere
  else
     # do something with the errors
  end
end

我一直觉得像将引擎与汽车相关联这样的事情是由 Rails 自动完成的，但我不知道如何让他做到.

I always felt that stuff, like associating an engine to a car, are done automatically by Rails, but I don't know how to make him do it.

切换 has_one 和 belongs_to 关联是实现这一目标的唯一方法吗?

Is switching the has_one and belongs_to associations the only way to achieve this?

我迷路了，我觉得我在这里错过了一些非常基本的东西.

I am lost and I feel like I'm missing something very basic here.

推荐答案

你应该使用 engine_id

<%= f.collection_select :engine_id, Engine.all, :id, :name %>

UPD

至于 Engine 不属于 Car，所以你应该在这里使用嵌套属性.此截屏视频对您非常有用:

as far as Engine is not belongs_to Car so you shoulduse Nested Attributes here. This screencast will be very useful for you:

• http://railscasts.com/episodes/196-nested-模型形式部分 1
• http://railscasts.com/episodes/197-nested-模型形式第 2 部分

结帐 API:http://apidock.com/rails/ActiveRecord/NestedAttributes/ClassMethods/accepts_nested_attributes_for

简短介绍:

class Car
  has_one :engine
  accepts_nested_attributes_for :engine
end

并以您的形式:

<%= form_for @car ... do |f| %>
  ...
  <%= f.fields_for :engine do |b| %>
    <%= b.collection_select :id, Engine.all, :id, :name %>
    ...
  <% end %>
  ...
<% end %>

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