系统检查框架使一系列静态检测和校验的方法，用来在Django项目启动的时候判断是否有异常的。它一般用于识别出问题并且提示如何解决这个问题。

检测函数可以在check 方法中触发，在使用runserver和migrate的时候也会被触发。不过出于性能上的考虑，checks不会在WSGI中被触发，所以这种时候需要自己执行check

检查的结果会在控制台上展现，假如你觉得不需要，可以在配置文件中使用SILENCED_SYSTEM_CHECKS就不会警告了

编写你自己的校验器

from django.core.checks import Error, register

@register()
def example_check(app_configs, **kwargs):
    errors = []
    # ... your check logic here
    if check_failed:
        errors.append(
            Error(
                'an error',
                hint='A hint.',
                obj=checked_object,
                id='myapp.E001',
            )
        )
    return errors

模型校验器

字段校验

from django.core import checks
from django.db import models

class RangedIntegerField(models.IntegerField):
    def __init__(self, min=None, max=None, **kwargs):
        super(RangedIntegerField, self).__init__(**kwargs)
        self.min = min
        self.max = max

    def check(self, **kwargs):
        # Call the superclass
        errors = super(RangedIntegerField, self).check(**kwargs)

        # Do some custom checks and add messages to `errors`:
        errors.extend(self._check_min_max_values(**kwargs))

        # Return all errors and warnings
        return errors

    def _check_min_max_values(self, **kwargs):
        if (self.min is not None and
                self.max is not None and
                self.min > self.max):
            return [
                checks.Error(
                    'min greater than max.',
                    hint='Decrease min or increase max.',
                    obj=self,
                    id='myapp.E001',
                )
            ]
        # When no error, return an empty list
        return []

模型校验

class MyModel(models.Model):
    @classmethod
    def check(cls, **kwargs):
        errors = super(MyModel, cls).check(**kwargs)
        # ... your own checks ...
        return errors