如何为has_and_belongs_to_many关系创建下拉列表?

时间:2013-01-30 13:08:16

标签: html ruby ruby-on-rails-3 model has-and-belongs-to-many

以下是我的模特:

class ThesisGroup < ActiveRecord::Base
  belongs_to :course
  has_and_belongs_to_many :students

  attr_accessible :code, :title, :course_id
end

class Student < ActiveRecord::Base
  has_and_belongs_to_many :thesis_groups

  attr_accessible :email, :lastnames, :names
end

class CreateThesisGroupStudentJoinTable < ActiveRecord::Migration  
  def change
    create_table :thesis_groups_students, :id => false do |t|
      t.integer :thesis_group_id
      t.integer :student_id
    end
  end
end

在我的控制器中,用于编辑ThesisGroups:

def update
    @thesis_group = ThesisGroup.find(params[:id])

    respond_to do |format|
      if @thesis_group.update_attributes(params[:thesis_group])
        format.html { redirect_to @thesis_group, notice: 'Thesis group was successfully updated.' }
        format.json { head :no_content }
      else
        format.html { render action: "edit" }
        format.json { render json: @thesis_group.errors, status: :unprocessable_entity }
      end
    end
  end

在我的视图中,我需要能够看到N个下拉列表;每个学生与当前的ThesisGroup建立关系。

我尝试了以下操作,但收到错误undefined method map for #<ThesisGroup:0x007f76b8c9d4d0>

<div class="control-group">
  <%= f.label :student %>
  <div class="controls">
    <%= f.collection_select 'student_ids', @thesis_group, :id, :names %>
  </div>
</div>

我需要为学生提供N个选择元素,并且在编辑此表单时,先前选择的元素显示为已选中。 Rails有办法解决这个问题吗?

我可以遍历student_ids集合,例如:

<%= student_ids.each do |s| %>
  generate html select element with 's'
<% end %>

1 个答案:

答案 0 :(得分:0)

您的accepts_nested_attributes_for :students模型中需要ThesisGroup

<%= field_set_tag 'Alumnos' do %>
  <%= f.fields_for :students do |student| %>
    <%= student.label :name, 'Student' %>
    <%= student.collection_select :student_id, Student.all, :id, :name %>
  <% end %>
<% end %>

编辑:我突然对collection_select中的参数不太确定:(