Ruby-on-rails 在此操作中多次调用渲染和/或重定向。

Render and/or redirect were called multiple times in this action..?

提问by Jonah Katz

I keep getting the DoubleRenderError and I cannot figure out why! Basically, I have an action that calls another action that checks a user inputted query for errors, and if theres an error, its stops and displays the error. But when i type in a query with an error, that when i get the double render! Any suggstions?

我不断收到 DoubleRenderError，但我不知道为什么！基本上，我有一个动作调用另一个动作来检查用户输入的查询是否有错误，如果有错误，它会停止并显示错误。但是当我输入一个错误的查询时，当我得到双重渲染时！有什么建议吗？

Heres the error checker action:

这是错误检查器操作：

def if_user_formulated_request_properly
    unless request.post?
      flash[:error] = "This page can only be accessed through the search page. (POST request only)"
 redirect_to(:action => "index") and return
    end

    if params[:query].blank?
      flash[:error] = "Search criteria can not be blank"
redirect_to(:action => "index") and  return
    end

    if !(params[:query] =~ /-/)
      flash[:error] = "( Format of search criteria is wrong.<br /> Should be [IXLSpecClass value][year]-[Message ID] for exam
ple GP07-8)"
redirect_to(:action => "index") and  return
    end

    if !(QueryParser.expression.match(params[:query]))
      flash[:error] = %( Format of search criteria is wrong.<br />Should be [IXLSpecClass value][year]-[Message ID] for examp
le GP07-8)
redirect_to(:action => "index") and return
  end
 yield

And just in case you need the action calling this action..

以防万一您需要调用此操作的操作..

 def show
        if_user_formulated_request_properly do
        @statuses = IXLStatus.find(:all)
        @input_messages = InputMessage.search_by(params[:query].stri
p) unless params[:query].blank?
        @query = params[:query]
        end
        respond_to do |format|
          format.html #default rendering
        end
        end
  end

UPDATE

更新

Also forgot to mention, this originally was a rails 2 app and was working, this error started when i upgraded to rails 3 (i believe), so maybe rails 3 does something different with and return?

还忘了提及，这最初是一个 rails 2 应用程序并且正在运行，当我升级到 rails 3 时开始出现此错误（我相信），所以也许 rails 3 与and return?

回答by Benoit Garret

You're only returning from the if_user_formulated_request_properlymethod, which means both the redirect_toand the respond_todo a render.

您只是从该if_user_formulated_request_properly方法返回，这意味着 theredirect_to和 therespond_to都进行渲染。

You could try this:

你可以试试这个：

def user_formulated_request_properly?
  unless request.post?
    flash[:error] = "This page can only be accessed through the search page. (POST request only)"
    return false
  end

  if params[:query].blank?
    flash[:error] = "Search criteria can not be blank"
    return false
  end

  if !(params[:query] =~ /-/)
    flash[:error] = "( Format of search criteria is wrong.<br /> Should be [IXLSpecClass value][year]-[Message ID] for example GP07-8)"
    return false
  end

  if !(QueryParser.expression.match(params[:query]))
    flash[:error] = %( Format of search criteria is wrong.<br />Should be [IXLSpecClass value][year]-[Message ID] for example GP07-8)
    return false
  end

  return true
end


def show
  if user_formulated_request_properly?
    @statuses = IXLStatus.find(:all)
    @input_messages = InputMessage.search_by(params[:query].strip) unless params[:query].blank?
    @query = params[:query]
  else
    redirect_to(:action => "index") and return
  end

  respond_to do |format|
    format.html #default rendering
  end
end

回答by Hiep Dinh

This my solution for some case:

这是我针对某些情况的解决方案：

"The underlying reason is that some part of the response_body is assigned before the error is triggered.

“根本原因是在触发错误之前分配了 response_body 的某些部分。

You could try clearing the response body before calling render in the exception handler."

您可以尝试在异常处理程序中调用 render 之前清除响应正文。”

def render_400
  # Clear the previous response body to avoid a DoubleRenderError
  # when redirecting or rendering another view
  self.response_body = nil

  render(nothing: true, status: 400)
end

Source: DoubleRenderError in Rails 4.1 when rescuing from InvalidCrossOriginRequest

来源： 从 InvalidCrossOriginRequest 救援时 Rails 4.1 中的 DoubleRenderError