Django4全栈进阶之路21 项目实战（在线报修）：创建App应用和Model模型

创建应用App
- ```
python manage.py startapp RepairApp
```
创建模型

　　　　在models.py文件中定义一个Repair模型来表示报修单，其中包含以下字段：

repair_id: 报修单号
repair_time: 报修时间
repair_person: 报修人
problem_description: 问题描述
service_person: 接单人
response_time: 首次回应时间
progress: 处理进度

from django.db import models

# Create your models here.
from django.db import models
import datetime

from django.db.models.signals import pre_save
from django.dispatch import receiver

# 报修单状态choices
STATUS_CHOICES = (
    ('1', '待受理'),
    ('2', '处理中'),
    ('3', '已完成'),
    ('4', '已撤销'),
)


class Repair(models.Model):
    repair_id = models.CharField(max_length=20, unique=True, verbose_name="报修单号")
    repair_time = models.DateTimeField(auto_now_add=True, verbose_name="报修时间")
    emp_id = models.CharField(max_length=20)
    repair_person = models.CharField(max_length=20, verbose_name="报修人")
    repair_description = models.TextField(verbose_name="问题描述")
    receiver = models.CharField(max_length=20, verbose_name="接单人", null=True, blank=True)
    first_response_time = models.DateTimeField(null=True, blank=True, verbose_name="首次回应时间")
    process_status = models.CharField(max_length=1, choices=STATUS_CHOICES, default='1', verbose_name="处理进度")
    created_time = models.DateTimeField(auto_now_add=True, verbose_name="创建时间")
    update_time = models.DateTimeField(auto_now=True, verbose_name="最后修改时间")

    def __str__(self):
        return self.repair_id

    class Meta:
        verbose_name = "报修单"
        verbose_name_plural = "报修单"
        ordering = ['-repair_time']


@receiver(pre_save, sender=Repair)
def auto_generate_repair_id(sender, instance, **kwargs):
    if not instance.repair_id:
        # 生成年月
        year_month = datetime.datetime.now().strftime("%Y%m")
        # 查找当月最大的流水号
        last_repair = Repair.objects.filter(repair_id__startswith=year_month).order_by('-repair_id').first()
        if last_repair:
            # 如果存在，流水号为最大报修单号加1
            max_id = int(last_repair.repair_id[-4:])
            new_id = f"{year_month}{max_id + 1:04}"
        else:
            # 如果不存在，流水号从0001开始
            new_id = f"{year_month}0001"
        instance.repair_id = new_id