在Python Django Crispy Forms中处理异常

问题描述

我是Python 3.8.2 / Django 3.1.1的新手，我试图找出向模型中添加规则的正确方法，以便可以从表单和Web服务中调用它们，我遇到的问题是某些错误没有被正确捕获，并且正在生成500错误。

这是我的初始模型：

class TotalPoints(TimeStampedModel):
    course = models.ForeignKey(Course,on_delete=models.CASCADE,related_name='TotalPoints_Course',null=False,blank=False,verbose_name='Curso')
    kit = models.ForeignKey(Kit,related_name='TotalPoints_Kit',verbose_name='Kit')
    bought = models.PositiveIntegerField(default=0,verbose_name='Comprados')
    assigned = models.PositiveIntegerField(default=0,verbose_name='Asignados')
    available = models.PositiveIntegerField(default=0,verbose_name='disponibles')
    class Meta:
        db_table = 'app_totalpoints'
        constraints = [
            models.UniqueConstraint(fields=['course','kit'],name='app_totalpoints.course-kit')
        ]

将字段声明为PositiveIntegerField以避免出现负值

这是我的表单和CreateView

class TotalPointsForm(forms.ModelForm):
    class Meta:
        model = TotalPoints
        fields = ['id','course','kit','available','bought','assigned']

class TotalPointsCreateView(CreateView):
    model = TotalPoints
    form_class = TotalPointsForm
    template_name = 'app/form_base.html'
    success_url='../list/'

这是我的模板：

{# app/templates/app/form_base.html #}
{% load crispy_forms_tags %}
<!doctype html>
<html lang="en">
    <head lang="es">
        <Meta charset="utf-8">
        <Meta name="viewport" content="width=device-width,initial-scale=1,shrink-to-fit=no">
        <link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0/css/bootstrap.min.css" integrity="sha384-Gn5384xqQ1aoWXA+058RXPxPg6fy4IWvTNh0E263XmFcJlSAwiGgFAW/dAiS6JXm" crossorigin="anonymous">
        <link rel="stylesheet" type="text/css" href="https://cdn.datatables.net/1.10.22/css/jquery.dataTables.css">
        <title>{% block page_title %}{% endblock %}</title>
    </head>
    <body>
        <div class="container-fluid">
            <div class="jumbotron">
                <h1 class="display-4">{% block form_title %}{% endblock %}</h1>
                <p class="lead">{% block form_subtitle %}{% endblock %}
                {% if user.is_authenticated %}
                    ( Usuario: {{ user.get_username }} )
                {% else %}
                    ( Usuario no regisTrado. )
                {% endif %}
                </p>
                <hr class="my-4">
                <div id='form-errors'>{{ form_errors }}</div>
                <form method="post">
                    {% csrf_token %}
                    {{ form|crispy }}
                    <button type="submit" class="btn btn-success">Grabar</button>
                    <!-- <a class="btn btn-primary" href="../list" role="button">Cancelar</a> -->
                    <a class="btn btn-primary" href="#" onclick="location.href = document.referrer; return false;" role="button">Cancelar</a>
                </form>
            </div>
        </div>
        <script src="https://code.jquery.com/jquery-3.2.1.slim.min.js" integrity="sha384-KJ3o2DKtIkvYIK3UENzmM7KCkRr/rE9/Qpg6aAZGJwFDMVNA/GpGFF93hXpG5KkN" crossorigin="anonymous"></script>
        <script src="https://cdnjs.cloudflare.com/ajax/libs/popper.js/1.12.9/umd/popper.min.js" integrity="sha384-ApNbgh9B+Y1QKtv3Rn7W3mgPxhU9K/ScQsAP7hUibX39j7fakFPskvXusvfa0b4Q" crossorigin="anonymous"></script>
        <script src="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0/js/bootstrap.min.js" integrity="sha384-JZR6Spejh4U02d8jOt6vLEHfe/JQGiRRSQQxSfFWpi1MquVdAyjUar5+76PVCmYl" crossorigin="anonymous"></script>
        <script type="text/javascript" charset="utf8" src="https://cdn.datatables.net/1.10.22/js/jquery.dataTables.js"></script>
    </body>
</html>

到目前为止一切正常，并且保存错误的值会在表格上返回一条消息：

要实施的规则是：可用=已购买-已分配（无条件= Comprados-Asignados）

这是我尝试的第一个版本，修改了模型：

class TotalPoints(TimeStampedModel):
    course = models.ForeignKey(Course,name='app_totalpoints.course-kit')
        ]
    def save(self,*args,**kwargs):
        #AVAILABLE = BOUGHT - ASSIGNED
        self.available = self.bought - self.assigned
        super(TotalPoints,self).save(*args,**kwargs)

如果所有值均为正，则该规则有效并正确计算可用值

如果购买的价格为负，则正确的错误会显示在表格上，但是如果可用的价格为负（bougth

enter image description here

跟踪：

Traceback (most recent call last):
  File "/home/egarza/projects/python/DjangoRESTABC/django-rest-abc-env/lib/python3.8/site-packages/django/db/backends/utils.py",line 84,in _execute
    return self.cursor.execute(sql,params)
psycopg2.errors.CheckViolation: el nuevo registro para la relación «app_totalpoints» viola la restricción «check» «app_totalpoints_available_check»
DETAIL:  La fila que falla contiene (36,2020-10-19 21:16:05.356574+00,2020-10-20 15:57:39.007548+00,10,12,23,1,-2).


The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "/home/egarza/projects/python/DjangoRESTABC/django-rest-abc-env/lib/python3.8/site-packages/django/core/handlers/exception.py",line 47,in inner
    response = get_response(request)
  File "/home/egarza/projects/python/DjangoRESTABC/django-rest-abc-env/lib/python3.8/site-packages/django/core/handlers/base.py",line 179,in _get_response
    response = wrapped_callback(request,*callback_args,**callback_kwargs)
  File "/home/egarza/projects/python/DjangoRESTABC/django-rest-abc-env/lib/python3.8/site-packages/django/contrib/auth/decorators.py",line 21,in _wrapped_view
    return view_func(request,**kwargs)
  File "/home/egarza/projects/python/DjangoRESTABC/django-rest-abc-env/lib/python3.8/site-packages/django/views/generic/base.py",line 70,in view
    return self.dispatch(request,line 98,in dispatch
    return handler(request,**kwargs)
  File "/home/egarza/projects/python/DjangoRESTABC/django-rest-abc-env/lib/python3.8/site-packages/django/views/generic/edit.py",line 194,in post
    return super().post(request,line 142,in post
    return self.form_valid(form)
  File "/home/egarza/projects/python/DjangoRESTABC/django-rest-abc-env/lib/python3.8/site-packages/django/views/generic/edit.py",line 125,in form_valid
    self.object = form.save()
  File "/home/egarza/projects/python/DjangoRESTABC/django-rest-abc-env/lib/python3.8/site-packages/django/forms/models.py",line 460,in save
    self.instance.save()
  File "/home/egarza/projects/python/DjangoRESTABC/abc_project/app/models.py",line 138,in save
    super(TotalPoints,**kwargs)
  File "/home/egarza/projects/python/DjangoRESTABC/django-rest-abc-env/lib/python3.8/site-packages/django/db/models/base.py",line 753,in save
    self.save_base(using=using,force_insert=force_insert,File "/home/egarza/projects/python/DjangoRESTABC/django-rest-abc-env/lib/python3.8/site-packages/django/db/models/base.py",line 790,in save_base
    updated = self._save_table(
  File "/home/egarza/projects/python/DjangoRESTABC/django-rest-abc-env/lib/python3.8/site-packages/django/db/models/base.py",line 872,in _save_table
    updated = self._do_update(base_qs,using,pk_val,values,update_fields,line 926,in _do_update
    return filtered._update(values) > 0
  File "/home/egarza/projects/python/DjangoRESTABC/django-rest-abc-env/lib/python3.8/site-packages/django/db/models/query.py",line 803,in _update
    return query.get_compiler(self.db).execute_sql(CURSOR)
  File "/home/egarza/projects/python/DjangoRESTABC/django-rest-abc-env/lib/python3.8/site-packages/django/db/models/sql/compiler.py",line 1522,in execute_sql
    cursor = super().execute_sql(result_type)
  File "/home/egarza/projects/python/DjangoRESTABC/django-rest-abc-env/lib/python3.8/site-packages/django/db/models/sql/compiler.py",line 1156,in execute_sql
    cursor.execute(sql,params)
  File "/home/egarza/projects/python/DjangoRESTABC/django-rest-abc-env/lib/python3.8/site-packages/django/db/backends/utils.py",in execute
    return super().execute(sql,line 66,in execute
    return self._execute_with_wrappers(sql,params,many=False,executor=self._execute)
  File "/home/egarza/projects/python/DjangoRESTABC/django-rest-abc-env/lib/python3.8/site-packages/django/db/backends/utils.py",line 75,in _execute_with_wrappers
    return executor(sql,many,context)
  File "/home/egarza/projects/python/DjangoRESTABC/django-rest-abc-env/lib/python3.8/site-packages/django/db/backends/utils.py",params)
  File "/home/egarza/projects/python/DjangoRESTABC/django-rest-abc-env/lib/python3.8/site-packages/django/db/utils.py",line 90,in __exit__
    raise dj_exc_value.with_traceback(traceback) from exc_value
  File "/home/egarza/projects/python/DjangoRESTABC/django-rest-abc-env/lib/python3.8/site-packages/django/db/backends/utils.py",params)
django.db.utils.IntegrityError: el nuevo registro para la relación «app_totalpoints» viola la restricción «check» «app_totalpoints_available_check»
DETAIL:  La fila que falla contiene (36,-2).

我使用信号切换到pre_save中的规则，但是结果是相同的：版本02使用信号：

class TotalPoints(TimeStampedModel):
    course = models.ForeignKey(Course,name='app_totalpoints.course-kit')
        ]

@receiver(pre_save,sender=TotalPoints,dispatch_uid="totalpoints_presave")
def totalpoints_presave(sender,instance,**kwargs):
    instance.available = instance.bought - instance.assigned

那么这些规则应该在哪里实现，以便使表格清晰易懂，而Django可以正确处理错误？

已添加：

我知道我正在做一些计算方法，以便表单能够捕获错误，这是否意味着我必须在表单上复制规则并始终具有重复的验证？

模型上没有标准事件可以执行此计算吗？（我也通过Web服务调用模型，因此我需要规则通用）

我知道我可以使用@property，但是我需要数据库中的字段，因为它将稍后由另一个进程（非Python的一个）使用

我和旧的C＃/ Java程序员都在回收中，我可能犯了很明显的错误，所以请教育我，不要以为我了解完整的上下文。

谢谢。

部分答案

我修改了Melvyns的评论，并覆盖了clean方法：

class TotalPoints(TimeStampedModel):
    course = models.ForeignKey(Course,name='app_totalpoints.course-kit')
        ]
    def clean(self):
        super().clean()
        if self.assigned > self.bought:
            #OPTION 1 Raise on the Form
            #raise ValidationError('Asignados debe ser menor o igual a Comprados')
            #OPTION 2 Raise on the field
            raise ValidationError({'assigned': 'Asignados no debe ser mayor a Comprados.'})

现在，我在表单上收到正确的错误消息，但这是一种验证数据的round回方式：

解决方法

由于约束而保存数据库认为错误的内容时，会发生完整性错误。对于表单而言，现在为时已晚。

ModelForms在模型上调用full_clean()并将捕获任何验证错误，就像是表单错误一样。呼叫顺序为：

forms.forms.Form.is_valid（）
forms.forms.Form.full_clean（）
forms.models.ModelForm._post_clean（）
instance.full_clean（）=> ValidationErrors进入form.errors
1. 干净的田地
2. instance.clean（）
3. 验证唯一性
instance.save（）=>距离太远而无法冒起泡沫

因此，您可以在instance.clean（）进行验证，并确保引发ValidationErrors。相关阅读：

Form validation：

清理数据时进行表单验证。如果要自定义此过程，可以在许多地方进行更改，每个地方都有不同的用途。表单处理过程中运行三种清洁方法

Model validation

验证模型涉及三个步骤：

验证模型字段-Model.clean_fields（）整体验证模型-Model.clean（）验证字段唯一性-Model.validate_unique（）

这三个步骤都是在调用模型的full_clean（）方法时执行的。

django django django-crispy-forms django-models python python-3.x

在Python Django Crispy Forms中处理异常

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