如何创建视图的HAS_ONE关联？ [英] How do I create the view for the has_one association?

问题描述

所以，想象一下我这个模型：

So, imagine I have this model:

class Car
  has_one :engine
end

和发动机型号：

class Engine
  belongs_to :car
end

当我present的形式对于用户来说，这样他就可以创建一个新的车，我只想让他从可用引擎之一选择（可用的引擎将在选择，人口由 collection_select ）。问题是，如果我建场是这样的：

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 %>

当我试图挽救它，我会得到一个AssociationTypeMismatch说，它预期为引擎，但它得到的字符串。

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

这是要做到这一点？

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

我一直觉得这些东西，像一个引擎关联到一辆车，会被Rails自动完成，但我不知道该怎么让他做到这一点。

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.

时的切换 HAS_ONE 和 belongs_to的协会实现这一目标的唯一途径？

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

我很失落，我觉得我在这里缺少一些非常基本的。

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

推荐答案

您应该使用 engine_id

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

UPD

据引擎不是belongs_to的车让你shoulduse嵌套属性在这里。这截屏将是非常有用的你：

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-模型外形部分-1
• http://railscasts.com/episodes/197-nested-模型外形部分-2

• http://railscasts.com/episodes/196-nested-model-form-part-1
• http://railscasts.com/episodes/197-nested-model-form-part-2

结账API：<一href="http://apidock.com/rails/ActiveRecord/NestedAttributes/ClassMethods/accepts_nested_attributes_for" rel="nofollow">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

和表单中的：

<%= 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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