Rails 4动态表单嵌套属性没有隐藏输入

Question

之前我问了一个关于建立一个出勤列表来获取学生并建立一个检查列表来标记出勤率的问题，并提出了这个问题。

def new
    @attendance_list = @classroom.attendance_lists.new

    @attendance_list.attendances = @classroom.student_ids.map do |student_id|
      @attendance_list.attendances.build(student_id: student_id)
    end
end

def create
    @attendance_list = @classroom.attendance_lists.new(attendance_list_params)
    @attendance_list.classroom_id = params[:classroom_id]

    respond_to do |format|

end

参数

params.require(:attendance_list)
  .permit(:post_date, :remark, 
          attendances_attributes: [:student_id, :attended, :remarks ])

使用简单的字段

= simple_form_for [@school, @classroom, @attendance_list] do |f|
  = f.input :post_date
  = f.input :remark

    = f.simple_fields_for :attendances do |g|
      ** you see i needed a hidden student_id **
      = g.input :student_id, as: :hidden
      ...... 

型号

class AttendanceList < ActiveRecord::Base
  belongs_to :classroom
  has_many :attendances
  has_many :students, :through => :attendances

  accepts_nested_attributes_for :attendances
end

class Attendance < ActiveRecord::Base
  belongs_to :student
  belongs_to :attendance_list
end

class Classroom < ActiveRecord::Base
  belongs_to :school
  has_and_belongs_to_many :students
  has_many :attendance_lists

  validates :class_name, presence: true
end

如果没有隐藏的输入，我该怎么办，因为这条线似乎不起作用。

build(student_id: student_id)

Answer 1

class AttendanceList < ActiveRecord::Base
  belongs_to :classroom
  has_many :attendances
  has_many :students, :through => :attendances
  accepts_nested_attributes_for :attendances
end

class Attendance < ActiveRecord::Base
  belongs_to :student
  belongs_to :attendance_list
end

class Classroom < ActiveRecord::Base
  belongs_to :school
  has_and_belongs_to_many :students
  has_many :attendance_lists

  validates :class_name, presence: true
end

class Student < ActiveRecord::Base
  has_many :attendances
  has_many :attendance_lists, :through => :attendances
end

查看文件

= simple_form_for @student do |f|
  = f.simple_fields_for :attendances do |g|
      ** your code **