【一】切入点#

切入点form_obj.is_valid()

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def is_valid(self):
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    """Return True if the form has no errors, or False otherwise."""
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    return self.is_bound and not self.errors

如果 is_valid 要想返回True
- 那么 self.is_bound 要为True
- self.errors 要为 False

【二】self.is_bound#

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def __init__(self, data=None, files=None, auto_id='id_%s', prefix=None,
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             initial=None, error_class=ErrorList, label_suffix=None,
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             empty_permitted=False, field_order=None, use_required_attribute=None, renderer=None):
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    self.is_bound = data is not None or files is not None

data 是我们传入的数据
- 只要传入数据有值
- 那么 self.is_bound 一定是True

【三】self.errors#

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@property
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def errors(self):
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    """Return an ErrorDict for the data provided for the form."""
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    if self._errors is None:
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        self.full_clean()
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        return self._errors

forms组件所有的功能基本都出自这个方法

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def full_clean(self):
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    """
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        Clean all of self.data and populate self._errors and self.cleaned_data.
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        """
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    self._errors = ErrorDict()
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    if not self.is_bound:  # Stop further processing.
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        return
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    self.cleaned_data = {}
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    # If the form is permitted to be empty, and none of the form data has
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    # changed from the initial data, short circuit any validation.
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    if self.empty_permitted and not self.has_changed():
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        return
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    self._clean_fields() # 校验字段
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    self._clean_form()
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    self._post_clean()

【1】self._clean_fields() 校验字段 + 局部钩子#

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def _clean_fields(self):
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    for name, field in self.fields.items():  # 循环获取字段对象
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        # value_from_datadict() gets the data from the data dictionaries.
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        # Each widget type knows how to retrieve its own data, because some
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        # widgets split data over several HTML fields.
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        if field.disabled:
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            value = self.get_initial_for_field(field, name)
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        else:
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            # 获取字段对应的值
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            value = field.widget.value_from_datadict(self.data, self.files, self.add_prefix(name))
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        try:
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            if isinstance(field, FileField):
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                initial = self.get_initial_for_field(field, name)
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                value = field.clean(value, initial)
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            else:
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                value = field.clean(value)
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            self.cleaned_data[name] = value   # 将合法的字段添加到字典里
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            if hasattr(self, 'clean_%s' % name): # 利用反射获取局部钩子函数
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                value = getattr(self, 'clean_%s' % name)()  # 局部钩子需要有返回值
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                self.cleaned_data[name] = value
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        except ValidationError as e:
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            self.add_error(name, e)  # 添加提示信息

循环获取字段对象

局部钩子报错也可以使用 ValidationError 主动抛出异常
- 较为繁琐，一般不用

【2】_clean_form 全局钩子#

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def _clean_form(self):
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    try:
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        cleaned_data = self.clean() # 调用父类的clean方法或者自定义的clean方法
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    except ValidationError as e:
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        self.add_error(None, e)
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    else:
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        if cleaned_data is not None:
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            self.cleaned_data = cleaned_data

【3】_post_clean#

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def _post_clean(self):
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    """
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    An internal hook for performing additional cleaning after form cleaning
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    is complete. Used for model validation in model forms.
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    """
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    pass