调整

app/controllers/courses_controller.rb

@@ -1266,7 +1266,7 @@ class CoursesController < ApplicationController
         @all_members = @course.students
         search = params[:search] ? "#{params[:search].strip}" : ""   #用户名或学生学号id搜索
         group_id = params[:group_id]  #分班的班级id
-        @all_members = @all_members.where(course_group_id: group_id) unless group_id.blank?
+        @all_members = @all_members.where(course_group_id: group_id.map(&:to_i)) unless group_id.blank?
         unless search.blank?
           @all_members = @all_members.joins(user: [:user_extension]).where('concat(users.lastname, users.firstname) like ? or user_extensions.student_id like ?',"%#{search}%","%#{search}%")
         end