2024--Django平台开发-Django知识点（六）

发布时间：2024年01月10日

day06 Django知识点

今日概要：

Form和ModelForm组件【使用】【源码】
缓存【使用】
ORM【使用】
其他：ContentTypes、Admin、权限、分页、信号等

1.Form和ModelForm组件

背景：某个公司后台管理项目。

垃圾

def register(request):
    """ 用户注册 """
    # 1.获取提交数据
    mobile = request.POST.get("mobile")
    sms = request.POST.get("sms")
    name = request.POST.get("name")
    age = request.POST.get("age")
    email = request.POST.get("email")
    password = request.POST.get("password")
    
    # 2.校验判断（10行）
    # all([mobile,sms])
    # 正则表达式
    
    # 3.业务逻辑代码

框架（内置+第三方表单验证组件）

<form method="post">
    <input type="text" name="mobile1" />
    {{form.mobile1}}
    
    <input type="text" name="sms" />
    {{form.sms}}
    
    <input type="submit" value="提交" />
</form>

class MyForm(Form):
    mobile1 = forms.CharField(reg="\d{11}", required=True)
    sms = forms.CharField(required=True)

def register(request):
    """ 用户注册 """
    if request.method == "GET":
        # form = MyForm(instance={"mobile1":"18766666666","sms":"999"})
        form = MyForm()
        return render(request, "xxxxx.html",{"form":form})
    
    # 1.获取提交数据
    form = MyForm(request.POST)
    if form.is_valid():
        print(form.cleared_data)
    else:
        print(form.errors)
        
    # 3.业务逻辑代码
    return render(request, "xxxxx.html",{"form":form})

关于组件：表单验证、自动生成HTML标签、数据初始化（新建按钮、编辑按钮）、保持原来的数据。

1.1 初识Form组件

基于注册为例来进行测试。

详细见示例：1-form组件.zip

1.2 错误信息

在这里插入图片描述

1.3 展示所有的字段

对象和可迭代对象。

在这里插入图片描述

1.4 问题：关于样式

手动操作

class RegisterForm(forms.Form):
    v1 = forms.CharField(
        label="手机号",
        required=True,
        # max_length=19,
        # min_length=6,
        initial="武沛齐",
        validators=[RegexValidator(r'^\d{11}$', "手机号格式错误"), ],
        widget=forms.TextInput(attrs={"class":"form-control"}) # <input type="text" class="form-control"/>
    )
    v2 = forms.CharField(
        label="备注",
        required=True,
        widget=forms.Textarea(attrs={"class":"form-control"}) # <textarea class="form-control"/></textarea>
    )
    ...
    ....
    .....

{% for field in form %}
	<p>{{ field.label }} {{ field }} {{ field.errors.0 }}  </p>
{% endfor %}

自动操作（找到每个字段中的widget插件，再找到插件中的attrs属性，给他每个赋值**{“class”:“form-control”}**

class RegisterForm(forms.Form):
    v1 = forms.CharField(...,widget=forms.TextInput)
    v2 = forms.CharField(...,widget=forms.TextInput(attrs={"v1":"123"}))
    
    def __init__(self,*args,**kwargs):
        super().__init__(self,*args,**kwargs)
        for name,field in self.fields.items():
            if name == "v1":
                continue 
            if field.widget.attrs:
                field.widget.attrs.update({"class":"form-control"})
            else:
            	field.widget.attrs = {"class":"form-control"}

form = RegisterForm()                   # __init__
form = RegisterForm(data=request.POST)  # __init__

1.5 问题：通用父类

class BootStrapForm(object):
    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)
        for name, field in self.fields.items():
            field.widget.attrs = {"class": "form-control"}


class LoginForm(BootStrapForm, forms.Form):
    user = forms.CharField(label="用户名", widget=forms.TextInput)
    pwd = forms.CharField(label="密码", widget=forms.TextInput)


def login(request):
    form = LoginForm()
    return render(request, "login.html", {"form": form})

class BootStrapForm(forms.Form):
    def __init__(self, *args, **kwargs):
        # 不是找父类
        # 根据类的mro（继承关系），去找上个类
        # super().__init__(*args, **kwargs)
        for name, field in self.fields.items():
            field.widget.attrs = {"class": "form-control"}

class LoginForm(BootStrapForm):
    user = forms.CharField(label="用户名", widget=forms.TextInput)
    pwd = forms.CharField(label="密码", widget=forms.TextInput)

def login(request):
    form = LoginForm()
    return render(request, "login.html", {"form": form})

1.6 答疑

类的内部继承关系，是继续c3算法。

class A:
    pass

class B:
    pass

class C(B,A):
    pass

# [<class '__main__.C'>, <class '__main__.B'>, <class '__main__.A'>, <class 'object'>]
print(C.mro())

老师 假如我们通过继承BootStrapForm实现批量给field对象添加{'class': 'form-control'}属性，那还能添加判断是否存在属性，若存在则更新；不存在再进行添加吗

1.7 ModelForm

使用Form

创建Form类 + 定义字段

class LoginForm(forms.Form):
    user = forms.CharField(label="用户名", widget=forms.TextInput)
    pwd = forms.CharField(label="密码", widget=forms.TextInput)

视图

def login(request):
    if request.method == "GET":
        form = LoginForm()
        return render(request, "login.html", {"form": form})
    form = LoginForm(data=request.POST)
    if not form.is_valid():
        # 校验失败
        return render(request, "login.html", {"form": form})
    print(form.cleaned_data)
    # ...
    return HttpRespon("OK")

前端

<form>
    {% for field in form %}
    <p>{{ field.label }} {{ field }} {{ field.errors.0 }}</p>
    {% endfor %}
</form>

使用ModelForm

models.py

class UserInfo(models.Model):
    name = models.CharField(verbose_name="用户名", max_length=32)
    age = models.IntegerField(verbose_name="年龄")
    email = models.CharField(verbose_name="邮箱", max_length=128)

创建ModelForm

class LoginForm(forms.ModelForm):
    mobile = forms.CharFiled(label="手机号")
	class Meta:
        model = models.UserInfo
        fileds = ["name","age", "mobile"]

视图使用

def login(request):
    form = LoginModelForm()
    return render(request, "login.html", {"form": form})

页面

<form>
    {% for field in form %}
    <p>{{ field.label }} {{ field }} {{ field.errors.0 }}</p>
    {% endfor %}
</form>

注意：

后续进行增伤改查是基于数据库Models中的某个表，推荐使用：ModelForm；
如果要进行表单校验是与数据库的表无关直接使用Form。

1.8 ModelForm两个好的地方

1.8.1 初始化数据

Form

class LoginForm(BootStrapForm, forms.Form):
    user = forms.CharField(label="用户名", widget=forms.TextInput)
    pwd = forms.CharField(label="密码", widget=forms.TextInput)

def login(request):
    form = LoginForm(initial={"user": "武沛齐", "pwd": "123"})
    return render(request, "login.html", {"form": form})

在这里插入图片描述

ModelForm

class LoginModelForm(BootStrapForm, forms.ModelForm):
    mobile = forms.CharField(label="手机号", widget=forms.TextInput)

    class Meta:
        model = models.UserInfo
        fields = ["name", "age", "mobile"]
        widgets = {
            "age": forms.TextInput,
        }
        labels = {
            "age": "x2",
        }

    def clean_name(self):
        value = self.cleaned_data['name']
        # raise ValidationError("....")
        return value

def login(request):
    user_object = models.UserInfo.objects.filter(id=1).first()
    form = LoginModelForm(instance=user_object, initial={"mobile": "武沛齐"})
    return render(request, "login.html", {"form": form})

在这里插入图片描述

1.8.2 新建数据

Form组件

def login(request):
    if request.method == "GET":
    	form = LoginForm(initial={"user": "武沛齐", "pwd": "123"})
    	return render(request, "login.html", {"form": form})
    form = LoginForm(data=request.POST)
    if not form.is_valid():
        return render(request, "login.html", {"form": form})
    
    # form.cleaned_data
    # 手动读取字典，保存至数据库
    # models.UserInfo.objects.create(name=form.cleaned_data['xx'], pwd=form.cleaned_data['yy'])
    return HttpResponse("成功")

ModelForm组件

def login(request):
    if request.method == "GET":
    	form = LoginForm()
    	return render(request, "login.html", {"form": form})
    
    form = LoginForm(data=request.POST)
    if not form.is_valid():
        return render(request, "login.html", {"form": form})
    
    form.save() # 自动将数据新增到数据库
    return HttpResponse("成功")

1.8.3 更新数据

Form组件

def login(request):
    if request.method == "GET":
    	form = LoginForm(initial={"user": "武沛齐", "pwd": "123"})
    	return render(request, "login.html", {"form": form})
    form = LoginForm(data=request.POST)
    if not form.is_valid():
        return render(request, "login.html", {"form": form})
    
    # form.cleaned_data
    # 手动读取字典，保存至数据库
    # models.UserInfo.objects.create(name=form.cleaned_data['xx'], pwd=form.cleaned_data['yy'])
    # models.UserInfo.objects.filter(id=1).update(name=form.cleaned_data['xx'], pwd=form.cleaned_data['y'])
    return HttpResponse("成功")

ModelForm组件

def login(request):
    if request.method == "GET":
    	form = LoginModelForm()
    	return render(request, "login.html", {"form": form})
    
    user_object = model.UserInfo.object.filter(id=1).first()
    form = LoginModelForm(data=request.POST, instance=user_object)
    if not form.is_valid():
        return render(request, "login.html", {"form": form})
    
    form.save() # 更新id=1
    return HttpResponse("成功")

1.9 案例

用户登录【Form】
用户管理：增改【ModelForm】

2.Form相关源码

2.1 前置知识点

1.模板渲染

def login(request):
    
    # 1.打开login2.html文件读取内容 + 参数进行“替换” => 渲染  ==> 得到被替换完的字符串
    # 2.将字符串封装HttpReponse对象中，等待给用户返回。
	return render(request, 'login2.html', {"v1": "wupeiqi"})

def render(request, template_name, context=None, content_type=None, status=None, using=None):
    content = loader.render_to_string(template_name, context, request, using=using)
    #    template = get_template(template_name, using=using)
    #    content = template.render(context, request)
    return HttpResponse(content, content_type, status)

from django.shortcuts import HttpResponse
from django.template.loader import get_template


def v1(request):
    template = get_template("v1.html")
    text = template.render({"text": "张开"}, request)
    print(text)

    return HttpResponse("OK")

2.插件相关的类

class Widget(metaclass=MediaDefiningClass):

    def __init__(self, attrs=None):
        self.attrs = {} if attrs is None else attrs.copy()

    def render(self, name, value, attrs=None, renderer=None):
        # name="user" value="zhangkai"  attrs=None   self.attrs={'class': "c1", "id": "xx1"}
        context = self.get_context(name, value, attrs)
        
        return self._render(self.template_name, context, renderer)
    
    def get_context(self, name, value, attrs):
        return {
            "widget": {
                "name": name, # "user"
                "value": self.format_value(value), # "zhangkai"
                "attrs": self.build_attrs(self.attrs, attrs), # {'class': "c1", "id": "xx1"}
                "template_name": self.template_name, # "django/forms/widgets/text.html"
                # "type":"text"
            },
        }

class Input(Widget):
    input_type = None  # Subclasses must define this.
    template_name = "django/forms/widgets/input.html"

    def __init__(self, attrs=None):
        if attrs is not None:
            attrs = attrs.copy()
            self.input_type = attrs.pop("type", self.input_type)
        super().__init__(attrs)


    def get_context(self, name, value, attrs):
        # {"widget":{"name":}   }
        context = super().get_context(name, value, attrs)
        context["widget"]["type"] = self.input_type
        return context
    
class TextInput(Input):
    input_type = "text"
    template_name = "django/forms/widgets/text.html"
    
    
class PasswordInput(Input):
    input_type = "password"
    template_name = "django/forms/widgets/password.html"

    def __init__(self, attrs=None, render_value=False):
        super().__init__(attrs)
        self.render_value = render_value

    def get_context(self, name, value, attrs):
        if not self.render_value:
            value = None
        return super().get_context(name, value, attrs)

from django.shortcuts import HttpResponse
from django.template.loader import get_template

from django import forms


def v1(request):
    template = get_template("v1.html")
    text = template.render({"text": "张开"}, request)
    print(text)

    return HttpResponse("OK")


def v2(request):
    # 1.执行 TextInput的 __init__方法
    obj = forms.TextInput(attrs={'class': "c1", "id": "xx1"})
    data_string = obj.render(name="user", value="张开")
    print(data_string)  # <input type='text' name='user' value="张开" class="c1"  id="xx1" />

    obj2 = forms.PasswordInput(attrs={'class': "c2"}, render_value=True)
    data_string = obj2.render(name="user", value="张开")
    print(data_string)

    return HttpResponse("OK")

3.init和new

class Foo(object):
    def __init__(self,name):
        self.name = name 

# 1. __new__ 去创建空对象 {}   -> 构造方法（创建对象）
# 2. __init__在对象中进行初始化 {"name":"武沛齐"}   -> 初始化方法
obj = Foo("武沛齐")

class Foo(object):
    def __init__(self, name):
        print("init初始化", self)
        self.name = name

    def __new__(cls, *args, **kwargs):
        obj = super().__new__(cls)
        print("new创建对象", obj)
        return obj


instance = Foo("wupeiqi")
print("得到对象", instance)

4.元类

说两句：

默认情况下，类都是由type创建；

class Info(object):
    city = "背景"

    def show(self):
        print("123")

# Info = type("Info", (object,), {"city": "背景", "show": lambda self: print(123)})

obj = Info()
print(obj.city)
obj.show()

想要由其他的东西创建类，就可以使用metaclass进行指定。

class Info(object,metaclass=其他):
    city = "背景"

    def show(self):
        print("123")

class MyType(type):
    pass


class Info(object, metaclass=MyType):
    city = "背景"

    def show(self):
        print("123")

类是有type创建的，类又可以进行实例化，去创建对象。

class MyType(type):
    # def __init__(self, *args, **kwargs):
    #     super().__init__(*args, **kwargs)

    def __new__(cls, *args, **kwargs):
        clazz = super().__new__(cls, *args, **kwargs)
        clazz.base_declare = [11, 22, 33]
        return clazz


class Info(object, metaclass=MyType):
    city = "背景"

    def show(self):
        print("123")

print(Info.base_declare)

5.isintance

判断某个对象是否是某个类或其子类创建的对象。

class Foo(object):
    pass


class Info(object):
    pass


obj1 = Foo()
obj2 = Foo()

print(isinstance(obj1, Foo))
print(isinstance(obj2, Info))

class Field(object):
    pass


class CharField(Field):
    pass


class EmailField(Field):
    pass


class ImageField(Field):
    pass


obj1 = CharField()
obj2 = EmailField()
obj3 = ImageField()

print(isinstance(obj1, Field))
print(isinstance(obj2, Field))
print(isinstance(obj3, Field))

功能：很多对象可以判断这些对象，都是我Field的子类创建的对象。

2.2 Form组件-定义类

class DeclarativeFieldsMetaclass(MediaDefiningClass):
    """Collect Fields declared on the base classes."""

    def __new__(mcs, name, bases, attrs):
        # Collect fields from current class and remove them from attrs.
        attrs["declared_fields"] = {
            key: attrs.pop(key)
            for key, value in list(attrs.items())
            if isinstance(value, Field)
        }

        new_class = super().__new__(mcs, name, bases, attrs)

        # Walk through the MRO.
        declared_fields = {}
        for base in reversed(new_class.__mro__):
            # Collect fields from base class.
            if hasattr(base, "declared_fields"):
                declared_fields.update(base.declared_fields)

            # Field shadowing.
            for attr, value in base.__dict__.items():
                if value is None and attr in declared_fields:
                    declared_fields.pop(attr)

        new_class.base_fields = declared_fields
        new_class.declared_fields = declared_fields

        return new_class

from django import forms

class Form(BaseForm, metaclass=DeclarativeFieldsMetaclass):
    pass

class LoginForm(forms.Form):
    username = forms.CharField(label="用户名", required=True, widget=forms.TextInput)
    pwd = forms.CharField(label="密码", required=True, widget=forms.PasswordInput)

LoginForm类其实是由DeclarativeFieldsMetaclass创建的【new】【init】。

2.3 Form组件-创建类的对象

from django import forms

class LoginForm(forms.Form):
    username = forms.CharField(label="用户名", required=True, widget=forms.TextInput)
    pwd = forms.CharField(label="密码", required=True, widget=forms.PasswordInput)

form = LoginForm() # __new__   __init__

class BaseForm(RenderableFormMixin):
    field_order = None
    
    def __init__(self,data=None,files=None,auto_id="id_%s",prefix=None,initial=None,....,field_order=None,renderer=None):
        self.fields = copy.deepcopy(self.base_fields)
        self.order_fields(  self.field_order if field_order is None else field_order   )
        self.initial = initial or {}
        
        renderer = get_default_renderer()
        self.renderer = renderer
        
    def order_fields(self, field_order):

        if field_order is None:
            return
        fields = {}
        for key in field_order:
            try:
                fields[key] = self.fields.pop(key)
            except KeyError:  # ignore unknown fields
                pass
        fields.update(self.fields)  # add remaining fields in original order
        self.fields = fields

class Form(BaseForm, metaclass=DeclarativeFieldsMetaclass):
    pass


class LoginForm(forms.Form):
    username = forms.CharField(label="用户名", required=True, widget=forms.TextInput)
    pwd = forms.CharField(label="密码", required=True, widget=forms.PasswordInput)


form = LoginForm(initial={})

2.4 Form组件-对象.字段

class LoginForm(forms.Form):
    username = forms.CharField(label="用户名", required=True, widget=forms.TextInput)
    pwd = forms.CharField(label="密码", required=True, widget=forms.PasswordInput)

def v3(request):
    form = LoginForm()
    print(form['username'])  # form.username <input type="text" name="username" required id="id_username">
    
    return HttpResponse("OK")

class Foo(object):

    def __getitem__(self, item):
        return 999


obj = Foo()

print(obj)
print(obj['xxxx'])

class BoundField:
    "A Field plus data"

    def __init__(self, form, field, name):
        self.form = form    # Form对象
        self.field = field  #  forms.CharField(label="用户名", required=True, widget=forms.TextInput)
        self.name = name    # "username"
        self.html_name = form.add_prefix(name)
        self.html_initial_name = form.add_initial_prefix(name)
        self.html_initial_id = form.add_initial_prefix(self.auto_id)
        if self.field.label is None:
            self.label = pretty_name(name)
        else:
            self.label = self.field.label
        self.help_text = field.help_text or ""

    def __str__(self):
        """Render this field as an HTML widget."""
        return self.as_widget() # <input type="text" name="username" required id="id_username">


    def as_widget(self, widget=None, attrs=None, only_initial=False):

        # 插件对象
        widget = widget or self.field.widget
        
        if self.field.localize:
            widget.is_localized = True
        attrs = attrs or {}
        attrs = self.build_widget_attrs(attrs, widget)
        if self.auto_id and "id" not in widget.attrs:
            attrs.setdefault(
                "id", self.html_initial_id if only_initial else self.auto_id
            )
        if only_initial and self.html_initial_name in self.form.data:
            # Propagate the hidden initial value.
            value = self.form._widget_data_value(
                self.field.hidden_widget(),
                self.html_initial_name,
            )
        else:
            value = self.value()

        # 字符串= 插件forms.TextInput对象.render  《input name='?' class=".."/>
        return widget.render(
            name=self.html_initial_name if only_initial else self.html_name,
            value=value,
            attrs=attrs,
            renderer=self.form.renderer,
        )

2.5 Form组件-可迭代对象

class MyForm(object):
    def __iter__(self):
        return iter([11, 22, 33, 44])


obj = MyForm()
for item in obj:
    print(item)

文章来源:https://blog.csdn.net/cxl0406/article/details/135514449
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