标签：获取对象 amp inpu word 连表 char core click ons
目录
# only
book_obj = models.Book.objects.filter(pk=1).only('title').first()
print(book_obj.title) # 直接获取
print(book_obj.price) # 需要访问数据库查询
# defer
book_obj = models.Book.objects.filter(pk=1).defer('title').first()
print(book_obj.title) # 需要访问数据库查询
print(book_obj.price) # 直接获取prefetch_related 内部是子查询操作, 按步骤查询多张表, 支持多对多表关系, 支持传入多个外键字段, 且每增加一个字段, 查询次数增加一次
prefetch_related方法耗时在查询次数上
# select_related
# 括号内只能放外键字段, 且外键字段类型是能是一对一或者一对多
# 内部是自动连表操作, 会将括号内外键字段关联的表, 与当前表拼接起来
# 括号内可以放多个外键字段, 用逗号隔开
# 耗时: 连表操作上
book_obj = models.Book.objects.filter(pk=1).select_related('publish').first()
print(book_obj.publish.name) # 访问一次数据库
book_obj = models.Book.objects.filter(pk=1).select_related().first()
print(book_obj.publish.name) # 访问两次数据库
# prefetch_related
# 内部是子查询操作, 按步骤查询多个表, 然后将查询的结果封装到对象中
# 括号内可放对个外键字段, 且支持多对多外键
# 每放一个字段, 就会多查询一张表
# 耗时: 查询次数上
book_obj = models.Book.objects.filter(pk=4).prefetch_related('publish', 'authors').first()
print(book_obj.publish.name)
print(book_obj.authors.all())# User表模型类
class User(models.Model):
username = models.CharField(max_length=255)
password = models.CharField(max_length=255)
# 创建数字和学历对应关系的元祖
edu_level_choices = (
(1, 'bachelor'),
(2, 'master'),
(3, 'doctor'),
(4, 'others')
)
# 将元祖赋值给choices参数, 字段类型为int
edu_level = models.IntegerField(choices=edu_level_choices)
+----+----------+----------+-----------+
| id | username | password | edu_level |
+----+----------+----------+-----------+
| 1 | alpha | 111 | 1 |
| 2 | bravo | 111 | 2 |
| 3 | charlie | 111 | 3 |
| 4 | delta | 111 | 4 |
| 5 | echo | 111 | 5 |
+----+----------+----------+-----------+对象.get_choices字段_display() 获取数字对应的值# 1.存在对应关系时
user_obj1 = models.User.objects.filter(pk=1).first()
print(user_obj1.edu_level) # 1
print(user_obj1.get_edu_level_display()) # bachelor
# 2.不存在对应关系时
user_obj5 = models.User.objects.filter(pk=5).first()
print(user_obj5.edu_level) # 5
print(user_obj5.get_edu_level_display()) # 5# 利用ajax实现页面不刷新的情况下, 现在输入的两个数的和
def ajax(request):
# 判断当前请求是否ajax请求
if request.is_ajax():
# print(request.POST) # ajax请求发送的数据也在request.POST当中
v1 = int(request.POST.get('v1'))
v2 = int(request.POST.get('v2'))
res = v1 + v2
return HttpResponse(res) # 只要有ajax, 三板斧就只返回给ajax的回调函数
return render(request, 'ajax_page.html')
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>ajax test</title>
<script src="https://cdn.bootcss.com/jquery/3.4.1/jquery.min.js"></script>
</head>
<body>
<input type="text" id="d1">+<input type="text" id="d2">=<input type="text" id="d3">
<button id="d4">提交</button>
<script>
$('#d4').on('click', function () {
// 开启ajax语法句式
$.ajax({
url: '', // 数据提交的后端地址, 不写就是往当前页面提交
type: 'post', // 提交方式, 默认还是get请求
data: {'v1': $('#d1').val(), 'v2': $('#d2').val()}, // 向后端提交的数据
success: function (data) { // 形参data是后端返回的结果
$('#d3').val(data)
}
})
})
</script>
</body>
</html>前端向后端发送数据:
form表单发送文本
编码: Content-Type: application/x-www-form-urlencoded
数据格式: username=‘bigb‘&password=‘123‘
后端针对urlencoded数据, 会自动解析并封装到request.POST中
Content-Type: multipart/form-data浏览器查看不到前后端交互时候, 一定确保数据格式与编码格式一致
ajax默认的编码格式也是: Content-Type: application/x-www-form-urlencoded, 因此也会封装到request.POST中
ajax默认是发送urlencoded编码格式的数据, 如果想发送json数据格式, 需要加一个参数: contentType: ‘application/json‘
$('#d1').on('click', function () {
$.ajax({
url: '',
type: 'post',
// 指定编码方式为: application/json
contentType: 'application/json',
data: JSON.stringify({'username': 'bigb', 'password': '123'}),
success: function (data) {
alert(123)
}
})
})def test(request):
print(request.body) # b'{"username":"bigb","password":"123"}'
return render(request, 'test.html')def test(request):
print(request.POST) # <QueryDict: {'username': ['bigb'], 'password': ['123']}>
print(request.FILES) # <MultiValueDict: {'upload_file': [<InMemoryUploadedFile: githublogo.jpg (image/jpeg)>]}
return render(request, 'test.html')username:<input type="text" name="username">
password:<input type="password" name="password">
upload_file:<input type="file" name="upload_file" id="d2">
<button id="d1">提交</button>
<script>
$('#d1').on('click', function () {
// 1.先生成一个内置对象
let MyFormData = new FormData
// 2.添加普通键值数据
MyFormData.append('username', 'bigb')
MyFormData.append('password', '123')
// 3.获取并添加文件对象
MyFormData.append('upload_file', $('#d2')[0].files[0])
$.ajax({
url: '',
type: 'post',
data: MyFormData,
// 发送文件必须要指定两个参数
contentType: false, // 不使用任何编码, MyFormData内部自带编码
processData: false, //不要处理数据
success: function (data) {
alert(123)
}
})
})
</script>
from django.core.serializers
# serialize()方法可以序列化queryset对象
def test1(request):
user_queryset = models.User.objects.all()
# 第一个参数: 数据格式json, 第二个参数: queryset对象
res = serializers.serialize('json', user_queryset)
return HttpResponse(res)
'''
[{"model": "app01.user", "pk": 1, "fields": {"username": "alpha", "password": "111", "edu_level": 1}}, {"model": "app01.user", "pk": 2, "fields": {"username": "bravo", "password": "111", "edu_level": 2}}, {"model": "app01.user", "pk": 3, "fields": {"username": "charlie", "password": "111", "edu_level": 3}}, {"model": "app01.user", "pk": 4, "fields": {"username": "delta", "password": "111", "edu_level": 4}}, {"model": "app01.user", "pk": 5, "fields": {"username": "echo", "password": "111", "edu_level": 5}}]
'''标签：获取对象 amp inpu word 连表 char core click ons
原文地址：https://www.cnblogs.com/bigb/p/11966794.html
