Rails slim form_for error“表单中的第一个参数不能包含nil或为空”

Question

我正在尝试同时创建许多缺席（针对不同的学生），而且我对rails非常陌生。我不断收到“表格中的第一个参数不能包含nil或为空”的错误。

我也想知道我是否需要一种新方法。

这是我的表格

= form_for @absent, url: absent_path, method: :post do |f|
  table.table
    thead
      tr
        th Name
        th Absent

    tbody
      - @students.each do |student|
        tr
          td = student.full_name
          td = f.check_box :student_ids, student.id, @absent.students.include?(student), name: "absent[student_ids][]", id: "student_id_#{student.id}"
  = f.submit 'Save'

这是我的控制器

def new
  @absent = Absent.new
end

def create
  absent_params[:student_ids].each do |student_id|
    @absent = Absent.new(student_id: student_id)
    if @absent.save
      redirect_to absent_path
    else
      render :index
    end
  end
end

private

def absent_params
  params.require(:absent).permit(
    :student_ids
  )
end

这是我的架构：

create_table "absents", force: true do |t|
    t.integer  "student_id"
    t.datetime "created_at"
    t.datetime "updated_at"
end

add_index "absents", ["student_id"], name: "index_absents_on_student_id", using: :btree

create_table "students", force: true do |t|
    t.string   "full_name"
    t.datetime "created_at"
    t.datetime "updated_at"
end

以下是我的模特：

class Student < ActiveRecord::Base

  has_many :absents, foreign_key: :student_id

end

class Absent < ActiveRecord::Base

  belongs_to :student, foreign_key: :student_id

end