根据lynda.com的截屏视频，Rails应该使用form_for（view）方法生成一个按钮，但事实并非如此。

Question

EDIT: The first question is my premise itself. Is rails/html SUPPOSED to generate a "Create Subject" button without me explicitly asking it to?

So here is the controller that is working with the view

class SubjectsController < ApplicationController

  def index
     list
    render('list')
  end

  def list
    @subjects = Subject.order("subjects.position ASC")
  end

  def show
    @subject = Subject.find(params[:id])
  end

  def new
    @subject = Subject.new(:name => 'default')
  end
  def create
    #instantiate a new object using form params
    @subject = Subject.new(params[:subject])
    #save the subject
    if @subject.save
      #if save succeeds redirect to list action
    else
      #if save fails, redisplay form
      render('new')
    end
  end
end

And here is the misbehaving view (html.erb) file which isn't generating my button

<%= link_to("<< Back to List", {:action => 'list'}, :class => 'back-link') %>

<div class="subject new">
  <h2>Create Subject</h2>

  <%=  form_for(:subject, :url => {:action => 'create'}) do |f| %>

  <table summary="Subject form fields">
    <tr>
      <th>Name</th>
      <td><%= f.text_field(:name) %></td>
    </tr>
    <tr>
      <th>Position</th>
      <td><%= f.text_field(:position) %></td>
    </tr>
    <tr>
      <th>Visible</th>
      <td><%= f.text_field(:visible) %></td>
    </tr>
  </table>
<% end %>
</div>

Currently, the output on the browser is:

'<< Back to List' (link)

<h2>Create Subject</h2>

Name     [blank-form]
Position [blank-form]
Visible  [blank-form]
[missing button location]

There is supposed to (according to lynda.com) be a button which says "Create Subject" in the missing button location, but it's not there.

Answer 1

Nothing in your code is supposed to generate a button.

You'll need to add:

<%= f.submit 'Create Subject' %>

inside the form. Maybe between </table> and <% end %>