Question

我有几个型号分别为 User ， Book 和问题。型号 Book 中有一个名为 remaining 的字段，其中包含可用图书数量的值。

我想要的东西：
如果有 0 本书可用，则发行一本书会关闭。

models.py

from django.db import models
from datetime import date, timedelta, datetime

class Book(models.Model):
    name = models.CharField(max_length=30)
    author_name = models.CharField(max_length=30)
    category = models.CharField(max_length=30)
    remaining = models.IntegerField()

    def __str__(self):
        return self.name

class Issue(models.Model):
    issue_id = models.CharField(max_length=10)
    roll = models.ForeignKey(User, on_delete=models.CASCADE)
    book_name = models.ForeignKey(Book, on_delete=models.CASCADE)
    issue_date = models.DateField(auto_now=False, auto_now_add=True)

    def save(self, *args, **kwargs):
        if not self.pk:
            super().save(*args, **kwargs)
            if self.book_name.remaining > 0:
                self.book_name.remaining -= 1
                self.book_name.save()
            elif self.book_name.remaining == 0:
                print('hi')
        else:
            super().save(*args, **kwargs)

admin.py

from django.contrib import admin
from django.contrib.auth.models import Group
from .models import User, Book, Issue

class BookAdmin(admin.ModelAdmin):
    list_display = ('name', 'author_name', 'remaining', 'category')
    list_filter = ('category', 'author_name')
    search_fields = ('name', 'author_name')


class IssueAdmin(admin.ModelAdmin):
    list_display = ('issue_id', 'issue_date', 'return_date', 'fine',)
    list_filter = ('issue_date',)
    search_fields = ('issue_id',)

admin.site.register(Book, BookAdmin)
admin.site.register(Issue, IssueAdmin)

我想在管理信息中心中实施此操作
问候

Answer 1

在清洁功能上，仅检查书籍是否可用。如果没有可用的记录，则会引发验证错误。

def clean(self, *args, **kwargs):
    from django.core.exceptions import ValidationError
    super().clean()
    if self.book_name.remaining < 1:
        raise ValidationError("No books available")
    else:
        self.book_name.remaining -= 1
        self.book_name.save()

在Django中满足条件时如何不执行操作

1 个答案: