collection_select 未保存/出错

Question

我正在尝试创建一个新的课程创建表单，其中包含下拉菜单以从教师表中选择教师。

当我将以下内容放入新课程表单视图中时，出现此错误：

当你没有预料到时，你得到了一个 nil 对象！

<%= collection_select(:Teacher, :id, @teachers, :id, :name, options = {:prompt => "Select a Teacher"}) %>

如果我把

<%= collection_select(:Teacher, :id, Teacher.find(:all), :id, :name, options = {:prompt => "Select a Teacher"}) %>

它创建带有正确下拉信息的表单，但它不会保存。

我的课程控制器创建方法如下所示

 def create
@course = Course.new(params[:course])

respond_to do |format|
  if @course.save
    format.html { redirect_to(@course, :notice => 'Course was successfully created.') }
    format.xml  { render :xml => @course, :status => :created, :location => @course }
  else
    format.html { render :action => "new" }
    format.xml  { render :xml => @course.errors, :status => :unprocessable_entity }
  end

Answer 1

像这样重写新操作

    def new
         @course = Course.new
         @teachers = Teachers.all

         respond_to do |format|
           format.html # new.html.erb
           format.xml  { render :xml => @course }
         end
      end

之后

<%= collection_select(:Teacher, :id, @teachers, :id, :name, options = {:prompt => "Select a Teacher"}) %>

应该可以工作