ORM版学员管理系统3

技术之博大精深

2020-05-01

老师信息管理

思考

三种方式创建多对多外键方式及其优缺点。

通过外键创建

class Class(models.Model):
    id = models.AutoField(primary_key=True)  # 主键
    cname = models.CharField(max_length=32)  # 班级名称
    first_day = models.DateField()  # 开班时间


class Teacher(models.Model):
    tname = models.CharField(max_length=32)


# 自定义第三张表，通过外键关联上面两张表
class Teacher2Class(models.Model):
    teacher = models.ForeignKey(to="Teacher")
    the_class = models.ForeignKey(to="Class")

    class Meta:
        unique_together = ("teacher", "the_class")

通过ManyToManyField创建

class Class(models.Model):
    id = models.AutoField(primary_key=True)  # 主键
    cname = models.CharField(max_length=32)  # 班级名称
    first_day = models.DateField()  # 开班时间


class Teacher(models.Model):
    tname = models.CharField(max_length=32)
    # 通过ManyToManyField自动创建第三张表
    cid = models.ManyToManyField(to="Class", related_name="teachers")

通过外键和ManyToManyField创建

class Class(models.Model):
    id = models.AutoField(primary_key=True)  # 主键
    cname = models.CharField(max_length=32)  # 班级名称
    first_day = models.DateField()  # 开班时间


class Teacher(models.Model):
    tname = models.CharField(max_length=32)
    # 通过ManyToManyField和手动创建第三张表
    cid = models.ManyToManyField(to="Class", through="Teacher2Class", through_fields=("teacher", "the_class"))


class Teacher2Class(models.Model):
    teacher = models.ForeignKey(to="Teacher")
    the_class = models.ForeignKey(to="Class")

    class Meta:
        unique_together = ("teacher", "the_class")

表结构设计

class Teacher(models.Model):
    tname = models.CharField(max_length=32)
    cid = models.ManyToManyField(to="Class", related_name="teachers")

老师信息列表

URL部分

url(r‘^teacher_list/$‘, app01_views.teacher_list, name="teacher_list"),

def teacher_list(request):
    teacher_list = models.Teacher.objects.all()
    return render(request, "teacher_list.html", {"teacher_list": teacher_list})

前端部分

<!DOCTYPE html>
<html lang="zh-CN">
<head>
  <meta charset="UTF-8">
  <meta http-equiv="x-ua-compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1">
  <title>老师信息页面</title>
</head>
<body>
<a href="{% url ‘add_teacher‘ %}">添加新老师</a>
<table border="1">
  <thead>
  <tr>
    <th>#</th>
    <th>id</th>
    <th>老师姓名</th>
    <th>授课班级</th>
    <th>操作</th>
  </tr>
  </thead>
  <tbody>
  {% for teacher in teacher_list %}
    <tr>
      <td>{{ forloop.counter }}</td>
      <td>{{ teacher.id }}</td>
      <td>{{ teacher.tname }}</td>
      <td>
        {% for class in teacher.cid.all %}
          {% if forloop.last %}
            {{ class.cname }}
          {% else %}
            {{ class.cname }},
          {% endif %}
        {% endfor %}
      </td>
      <td>
        <a href="{% url ‘delete_teacher‘ teacher.id %}">删除</a>
        <a href="{% url ‘edit_teacher‘ teacher.id %}">编辑</a>
      </td>
    </tr>
  {% endfor %}
  </tbody>
</table>
</body>
</html>

删除老师信息

URL部分

url(r‘^delete_teacher/(?P<tid>\d+)$‘, app01_views.delete_teacher, name="delete_teacher"),

视图部分

def delete_teacher(request, tid):
    models.Teacher.objects.filter(id=tid).delete()
    return redirect(reverse("teacher_list"))

前端部分

在老师列表页面添加一个删除的链接。

<a href="{% url ‘delete_teacher‘ teacher.id %}">删除</a>

添加老师信息

URL部分

url(r‘^add_teacher/$‘, app01_views.add_teacher, name="add_teacher"),

视图部分

def add_teacher(request):
    if request.method == "POST":
        tname = request.POST.get("tname")
        class_ids = request.POST.getlist("class_id")
        new_teacher = models.Teacher.objects.create(tname=tname)
        # 查询出所有被选中的班级信息
        class_objs = models.Class.objects.filter(id__in=class_ids)
        # 将老师的授课班级设置为选中的班级， 以下四种都可以，注意什么时候加*
        new_teacher.cid.set(class_objs)
        # new_teacher.cid.add(*class_objs)
        # new_teacher.cid.add(*class_ids)
        # new_teacher.cid.set(class_ids)
        new_teacher.save()
        return redirect(reverse("teacher_list"))

    class_list = models.Class.objects.all()
    return render(request, "add_teacher.html", {"class_list": class_list})

前端部分

<!DOCTYPE html>
<html lang="zh-CN">
<head>
  <meta charset="UTF-8">
  <meta http-equiv="x-ua-compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1">
  <title>添加老师</title>
</head>
<body>
<form action="{% url ‘add_teacher‘ %}" method="post">
  {% csrf_token %}
  <p>老师姓名：<input type="text" name="tname"></p>
  <label for="class_id">授课班级：</label>
    <select name="class_id" id="class_id" multiple>
      {% for class in class_list %}
        <option value="{{ class.id }}">{{ class.cname }}</option>
      {% endfor %}
    </select>
    <p><input type="submit" value="提交"></p>
</form>
</body>
</html>

编辑老师信息

URL部分

url(r‘^edit_teacher/(?P<tid>\d+)$‘, app01_views.edit_teacher, name="edit_teacher"),

视图部分

def edit_teacher(request, tid):
    teacher_obj = models.Teacher.objects.get(id=tid)
    class_list = models.Class.objects.all()

    if request.method == "POST":
        tname = request.POST.get("tname")
        class_ids = request.POST.getlist("class_id")
        # 更新老师相关信息
        teacher_obj.tname = tname
        teacher_obj.cid.set(class_ids)
        teacher_obj.save()  # 一定记得更新完要保存
        return redirect(reverse("teacher_list"))

    return render(request, "edit_teacher.html", {"class_list": class_list, "teacher": teacher_obj})

前端部分

<!DOCTYPE html>
<html lang="zh-CN">
<head>
  <meta charset="UTF-8">
  <meta http-equiv="x-ua-compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1">
  <title>编辑老师信息</title>
</head>
<body>
<form action="{% url ‘edit_teacher‘ teacher.id %}" method="post">
  {% csrf_token %}
  <p>老师姓名：<input type="text" name="tname" value="{{ teacher.tname }}"></p>
  <label for="class_id">授课班级：</label>
  <select name="class_id" id="class_id" multiple>
    {% for class in class_list %}
      {% if class in teacher.cid.all %}
        <option value="{{ class.id }}" selected>{{ class.cname }}</option>
      {% else %}
        <option value="{{ class.id }}">{{ class.cname }}</option>
      {% endif %}
    {% endfor %}
  </select>
  <p><input type="submit" value="提交"></p>
</form>
</body>
</html>

多对多操作

正向查询（由老师表查询班级表）

>>> teacher_obj = models.Teacher.objects.first()
>>> teacher_obj.cid.all()  # 查询该老师授课的所有班级
<QuerySet [<Class: Class object>, <Class: Class object>]>

反向查询（由班级表反向查询老师表）

>>> class_obj = models.Class.objects.first()
>>> class_obj.teachers.all()  # 此处用到的是related_name，如果不设置的话就用默认的表名_set
<QuerySet [<Teacher: Teacher object>, <Teacher: Teacher object>, <Teacher: Teacher object>]>

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