在 Rails 中，当资源创建操作失败并调用 render :new 时，为什么 URL 必须更改为资源的索引 url? [英] In Rails when a resource create action fails and calls render :new, why must the URL change to the resource's index url?

问题描述

我有一个名为书籍的资源.它在我的路由文件中正确列为资源.

I have a resource called Books. It's listed as a resource properly in my routes file.

我有一个新操作，它为新视图提供了标准:

I have a new action, which gives the new view the standard:

@book = Book.new

在模型上，有一些属性是通过存在来验证的，所以如果保存操作失败，就会产生错误.

On the model, there are some attributes which are validated by presence, so if a save action fails, errors will be generated.

在我的控制器中:

@book = Book.create
...  # some logic
if @book.save
  redirect_to(@book)
else
  render :new
end

这是非常标准的；使用 render:new 的基本原理是将对象传递回视图并报告错误、重新填写表单条目等.

This is pretty standard; and the rationale for using render:new is so that the object is passed back to the view and errors can be reported, form entries re-filled, etc.

这有效，除了每次我被发送回表单(通过渲染:new)时，我的错误都会显示出来，但我的 URL 是 INDEX URL，即

This works, except every time I'm sent back to the form (via render :new), my errors show up, but my URL is the INDEX URL, which is

/books

而不是

/books/new

这是我最开始的地方.我看过其他几篇关于这个问题的帖子，但没有答案.至少，人们会假设它会让你进入/books/create，我也有一个视图文件(在这种情况下与 new 相同).

Which is where I started out in the first place. I have seen several others posts about this problem, but no answers. At a minimum, one would assume it would land you at /books/create, which I also have a view file for (identical to new in this case).

我可以做到:

# if the book isn't saved then
flash[:error] = "Errors!"
redirect_to new_book_path

但是随后@book 数据以及错误消息都丢失了，这就是拥有表单和操作等的全部意义.

But then the @book data is lost, along with the error messages, which is the entire point of having the form and the actions, etc.

为什么 render :new 将我登陆到/books，我的索引操作，通常该 URL 调用 INDEX 方法，该方法列出所有书籍?

Why is render :new landing me at /books, my index action, when normally that URL calls the INDEX method, which lists all the books?

推荐答案

它实际上 将您发送到创建路径.它位于 create 操作中，其路径为 /books，使用 HTTP 方法 POST.这看起来与索引路径 /books 相同，但索引路径使用 HTTP 方法 GET.rails 路由代码在确定要调用的操作时会考虑该方法.验证失败后，您仍处于创建操作中，但您正在呈现 new 视图.这有点令人困惑，但是像 render :new 这样的行实际上根本没有调用新操作；它仍在运行创建操作，并告诉 Rails 渲染新的视图.

It actually is sending you to the create path. It's in the create action, the path for which is /books, using HTTP method POST. This looks the same as the index path /books, but the index path is using HTTP method GET. The rails routing code takes the method into account when determining which action to call. After validation fails, you're still in the create action, but you're rendering the new view. It's a bit confusing, but a line like render :new doesn't actually invoke the new action at all; it's still running the create action and it tells Rails to render the new view.

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