结合使用 super 和 django ModelForm class 来改变 __init__ 方法
Usage of super in conjunction with a django ModelForm class to alter the __init__ method
在尝试一些代码创意时，我偶然发现了一个我似乎无法理解的问题。
请忽略我为什么尝试这样做，问题是为什么它不起作用；）
所以我想创建一个表单类，在其中覆盖基类的 __init__ 方法，但只是想复制它。
基本上我想做的是：
class A():
def __init(self, a, b, c)__:
self.a = a
self.b = b
self.c = c
class B(A):
def __init__(self, a, b, c):
super(B, self).__init__( a, b, c)
# Do some stuff that was not implemented#
我希望 B 的 __init__ 方法能够像没有任何变化一样工作，除了最后添加的内容。但是，在我的示例中，肯定发生了一些变化，因为我的表单之后不再工作：
class SignUpForm_test(forms.ModelForm):
password_confirmed = forms.CharField(widget=forms.PasswordInput())
# --> This is the important stuff, the rest is just for completeness <--#
#########################################################################
def __init__(self, data=None, files=None, auto_id='id_%s', prefix=None,
initial=None, error_class=ErrorList, label_suffix=None,
empty_permitted=False, instance=None, use_required_attribute=None,
renderer=None):
super().__init__( data=None, files=None, auto_id='id_%s', prefix=None,
initial=None, error_class=ErrorList, label_suffix=None,
empty_permitted=False, instance=None, use_required_attribute=None,
renderer=None)
#########################################################################
class Meta:
model = get_user_model()
fields = (
"username",
"email",
"password"
)
def clean_password_confirmed(self):
password = self.cleaned_data.get('password')
password_confirmed = self.cleaned_data.get('password_confirmed')
if password and password_confirmed:
if password != password_confirmed:
raise ValidationError(
message ='Passwörter müssen übereinstimmen',
code ='password_mismatch',
)
# password_validation.validate_password(password_confirmed)
return password_confirmed
感谢您帮助理解这一点！
这里是ModelForm和相关BaseModelForm的源码，不用找了：
class BaseModelForm(BaseForm):
def __init__(self, data=None, files=None, auto_id='id_%s', prefix=None,
initial=None, error_class=ErrorList, label_suffix=None,
empty_permitted=False, instance=None, use_required_attribute=None,
renderer=None):
opts = self._meta
if opts.model is None:
raise ValueError('ModelForm has no model class specified.')
if instance is None:
# if we didn't get an instance, instantiate a new one
self.instance = opts.model()
object_data = {}
else:
self.instance = instance
object_data = model_to_dict(instance, opts.fields, opts.exclude)
# if initial was provided, it should override the values from instance
if initial is not None:
object_data.update(initial)
# self._validate_unique will be set to True by BaseModelForm.clean().
# It is False by default so overriding self.clean() and failing to call
# super will stop validate_unique from being called.
self._validate_unique = False
super().__init__(
data, files, auto_id, prefix, object_data, error_class,
label_suffix, empty_permitted, use_required_attribute=use_required_attribute,
renderer=renderer,
)
for formfield in self.fields.values():
apply_limit_choices_to_to_formfield(formfield)
def _get_validation_exclusions(self):
"""
For backwards-compatibility, exclude several types of fields from model
validation. See tickets #12507, #12521, #12553.
"""
exclude = []
# Build up a list of fields that should be excluded from model field
# validation and unique checks.
for f in self.instance._meta.fields:
field = f.name
# Exclude fields that aren't on the form. The developer may be
# adding these values to the model after form validation.
if field not in self.fields:
exclude.append(f.name)
# Don't perform model validation on fields that were defined
# manually on the form and excluded via the ModelForm's Meta
# class. See #12901.
elif self._meta.fields and field not in self._meta.fields:
exclude.append(f.name)
elif self._meta.exclude and field in self._meta.exclude:
exclude.append(f.name)
# Exclude fields that failed form validation. There's no need for
# the model fields to validate them as well.
elif field in self._errors:
exclude.append(f.name)
# Exclude empty fields that are not required by the form, if the
# underlying model field is required. This keeps the model field
# from raising a required error. Note: don't exclude the field from
# validation if the model field allows blanks. If it does, the blank
# value may be included in a unique check, so cannot be excluded
# from validation.
else:
form_field = self.fields[field]
field_value = self.cleaned_data.get(field)
if not f.blank and not form_field.required and field_value in form_field.empty_values:
exclude.append(f.name)
return exclude
def clean(self):
self._validate_unique = True
return self.cleaned_data
def _update_errors(self, errors):
# Override any validation error messages defined at the model level
# with those defined at the form level.
opts = self._meta
# Allow the model generated by construct_instance() to raise
# ValidationError and have them handled in the same way as others.
if hasattr(errors, 'error_dict'):
error_dict = errors.error_dict
else:
error_dict = {NON_FIELD_ERRORS: errors}
for field, messages in error_dict.items():
if (field == NON_FIELD_ERRORS and opts.error_messages and
NON_FIELD_ERRORS in opts.error_messages):
error_messages = opts.error_messages[NON_FIELD_ERRORS]
elif field in self.fields:
error_messages = self.fields[field].error_messages
else:
continue
for message in messages:
if (isinstance(message, ValidationError) and
message.code in error_messages):
message.message = error_messages[message.code]
self.add_error(None, errors)
def _post_clean(self):
opts = self._meta
exclude = self._get_validation_exclusions()
# Foreign Keys being used to represent inline relationships
# are excluded from basic field value validation. This is for two
# reasons: firstly, the value may not be supplied (#12507; the
# case of providing new values to the admin); secondly the
# object being referred to may not yet fully exist (#12749).
# However, these fields *must* be included in uniqueness checks,
# so this can't be part of _get_validation_exclusions().
for name, field in self.fields.items():
if isinstance(field, InlineForeignKeyField):
exclude.append(name)
try:
self.instance = construct_instance(self, self.instance, opts.fields, opts.exclude)
except ValidationError as e:
self._update_errors(e)
try:
self.instance.full_clean(exclude=exclude, validate_unique=False)
except ValidationError as e:
self._update_errors(e)
# Validate uniqueness if needed.
if self._validate_unique:
self.validate_unique()
def validate_unique(self):
"""
Call the instance's validate_unique() method and update the form's
validation errors if any were raised.
"""
exclude = self._get_validation_exclusions()
try:
self.instance.validate_unique(exclude=exclude)
except ValidationError as e:
self._update_errors(e)
def _save_m2m(self):
"""
Save the many-to-many fields and generic relations for this form.
"""
cleaned_data = self.cleaned_data
exclude = self._meta.exclude
fields = self._meta.fields
opts = self.instance._meta
# Note that for historical reasons we want to include also
# private_fields here. (GenericRelation was previously a fake
# m2m field).
for f in chain(opts.many_to_many, opts.private_fields):
if not hasattr(f, 'save_form_data'):
continue
if fields and f.name not in fields:
continue
if exclude and f.name in exclude:
continue
if f.name in cleaned_data:
f.save_form_data(self.instance, cleaned_data[f.name])
def save(self, commit=True):
"""
Save this form's self.instance object if commit=True. Otherwise, add
a save_m2m() method to the form which can be called after the instance
is saved manually at a later time. Return the model instance.
"""
if self.errors:
raise ValueError(
"The %s could not be %s because the data didn't validate." % (
self.instance._meta.object_name,
'created' if self.instance._state.adding else 'changed',
)
)
if commit:
# If committing, save the instance and the m2m data immediately.
self.instance.save()
self._save_m2m()
else:
# If not committing, add a method to the form to allow deferred
# saving of m2m data.
self.save_m2m = self._save_m2m
return self.instance
save.alters_data = True
class ModelForm(BaseModelForm, metaclass=ModelFormMetaclass):
pass
问题出在您的 super 通话中。不是复制传递给方法的变量，而是用默认值覆盖它们。改用这个
super().__init__( data=data, files=files, auto_id=auto_id, prefix=prefix,
initial=initial, error_class=error_class, label_suffix=label_suffix,
empty_permitted=empty_permitted, instance=instance, use_required_attribute=use_required_attribute,
renderer=renderer)
另一种选择是简单地捕获所有参数：
def __init__(self, *args, **kwargs):
super().__init__(*args, **kwargs)
在尝试一些代码创意时，我偶然发现了一个我似乎无法理解的问题。
请忽略我为什么尝试这样做，问题是为什么它不起作用；）
所以我想创建一个表单类，在其中覆盖基类的 __init__ 方法，但只是想复制它。
基本上我想做的是：
class A():
def __init(self, a, b, c)__:
self.a = a
self.b = b
self.c = c
class B(A):
def __init__(self, a, b, c):
super(B, self).__init__( a, b, c)
# Do some stuff that was not implemented#
我希望 B 的 __init__ 方法能够像没有任何变化一样工作，除了最后添加的内容。但是，在我的示例中，肯定发生了一些变化，因为我的表单之后不再工作：
class SignUpForm_test(forms.ModelForm):
password_confirmed = forms.CharField(widget=forms.PasswordInput())
# --> This is the important stuff, the rest is just for completeness <--#
#########################################################################
def __init__(self, data=None, files=None, auto_id='id_%s', prefix=None,
initial=None, error_class=ErrorList, label_suffix=None,
empty_permitted=False, instance=None, use_required_attribute=None,
renderer=None):
super().__init__( data=None, files=None, auto_id='id_%s', prefix=None,
initial=None, error_class=ErrorList, label_suffix=None,
empty_permitted=False, instance=None, use_required_attribute=None,
renderer=None)
#########################################################################
class Meta:
model = get_user_model()
fields = (
"username",
"email",
"password"
)
def clean_password_confirmed(self):
password = self.cleaned_data.get('password')
password_confirmed = self.cleaned_data.get('password_confirmed')
if password and password_confirmed:
if password != password_confirmed:
raise ValidationError(
message ='Passwörter müssen übereinstimmen',
code ='password_mismatch',
)
# password_validation.validate_password(password_confirmed)
return password_confirmed
感谢您帮助理解这一点！
这里是ModelForm和相关BaseModelForm的源码，不用找了：
class BaseModelForm(BaseForm):
def __init__(self, data=None, files=None, auto_id='id_%s', prefix=None,
initial=None, error_class=ErrorList, label_suffix=None,
empty_permitted=False, instance=None, use_required_attribute=None,
renderer=None):
opts = self._meta
if opts.model is None:
raise ValueError('ModelForm has no model class specified.')
if instance is None:
# if we didn't get an instance, instantiate a new one
self.instance = opts.model()
object_data = {}
else:
self.instance = instance
object_data = model_to_dict(instance, opts.fields, opts.exclude)
# if initial was provided, it should override the values from instance
if initial is not None:
object_data.update(initial)
# self._validate_unique will be set to True by BaseModelForm.clean().
# It is False by default so overriding self.clean() and failing to call
# super will stop validate_unique from being called.
self._validate_unique = False
super().__init__(
data, files, auto_id, prefix, object_data, error_class,
label_suffix, empty_permitted, use_required_attribute=use_required_attribute,
renderer=renderer,
)
for formfield in self.fields.values():
apply_limit_choices_to_to_formfield(formfield)
def _get_validation_exclusions(self):
"""
For backwards-compatibility, exclude several types of fields from model
validation. See tickets #12507, #12521, #12553.
"""
exclude = []
# Build up a list of fields that should be excluded from model field
# validation and unique checks.
for f in self.instance._meta.fields:
field = f.name
# Exclude fields that aren't on the form. The developer may be
# adding these values to the model after form validation.
if field not in self.fields:
exclude.append(f.name)
# Don't perform model validation on fields that were defined
# manually on the form and excluded via the ModelForm's Meta
# class. See #12901.
elif self._meta.fields and field not in self._meta.fields:
exclude.append(f.name)
elif self._meta.exclude and field in self._meta.exclude:
exclude.append(f.name)
# Exclude fields that failed form validation. There's no need for
# the model fields to validate them as well.
elif field in self._errors:
exclude.append(f.name)
# Exclude empty fields that are not required by the form, if the
# underlying model field is required. This keeps the model field
# from raising a required error. Note: don't exclude the field from
# validation if the model field allows blanks. If it does, the blank
# value may be included in a unique check, so cannot be excluded
# from validation.
else:
form_field = self.fields[field]
field_value = self.cleaned_data.get(field)
if not f.blank and not form_field.required and field_value in form_field.empty_values:
exclude.append(f.name)
return exclude
def clean(self):
self._validate_unique = True
return self.cleaned_data
def _update_errors(self, errors):
# Override any validation error messages defined at the model level
# with those defined at the form level.
opts = self._meta
# Allow the model generated by construct_instance() to raise
# ValidationError and have them handled in the same way as others.
if hasattr(errors, 'error_dict'):
error_dict = errors.error_dict
else:
error_dict = {NON_FIELD_ERRORS: errors}
for field, messages in error_dict.items():
if (field == NON_FIELD_ERRORS and opts.error_messages and
NON_FIELD_ERRORS in opts.error_messages):
error_messages = opts.error_messages[NON_FIELD_ERRORS]
elif field in self.fields:
error_messages = self.fields[field].error_messages
else:
continue
for message in messages:
if (isinstance(message, ValidationError) and
message.code in error_messages):
message.message = error_messages[message.code]
self.add_error(None, errors)
def _post_clean(self):
opts = self._meta
exclude = self._get_validation_exclusions()
# Foreign Keys being used to represent inline relationships
# are excluded from basic field value validation. This is for two
# reasons: firstly, the value may not be supplied (#12507; the
# case of providing new values to the admin); secondly the
# object being referred to may not yet fully exist (#12749).
# However, these fields *must* be included in uniqueness checks,
# so this can't be part of _get_validation_exclusions().
for name, field in self.fields.items():
if isinstance(field, InlineForeignKeyField):
exclude.append(name)
try:
self.instance = construct_instance(self, self.instance, opts.fields, opts.exclude)
except ValidationError as e:
self._update_errors(e)
try:
self.instance.full_clean(exclude=exclude, validate_unique=False)
except ValidationError as e:
self._update_errors(e)
# Validate uniqueness if needed.
if self._validate_unique:
self.validate_unique()
def validate_unique(self):
"""
Call the instance's validate_unique() method and update the form's
validation errors if any were raised.
"""
exclude = self._get_validation_exclusions()
try:
self.instance.validate_unique(exclude=exclude)
except ValidationError as e:
self._update_errors(e)
def _save_m2m(self):
"""
Save the many-to-many fields and generic relations for this form.
"""
cleaned_data = self.cleaned_data
exclude = self._meta.exclude
fields = self._meta.fields
opts = self.instance._meta
# Note that for historical reasons we want to include also
# private_fields here. (GenericRelation was previously a fake
# m2m field).
for f in chain(opts.many_to_many, opts.private_fields):
if not hasattr(f, 'save_form_data'):
continue
if fields and f.name not in fields:
continue
if exclude and f.name in exclude:
continue
if f.name in cleaned_data:
f.save_form_data(self.instance, cleaned_data[f.name])
def save(self, commit=True):
"""
Save this form's self.instance object if commit=True. Otherwise, add
a save_m2m() method to the form which can be called after the instance
is saved manually at a later time. Return the model instance.
"""
if self.errors:
raise ValueError(
"The %s could not be %s because the data didn't validate." % (
self.instance._meta.object_name,
'created' if self.instance._state.adding else 'changed',
)
)
if commit:
# If committing, save the instance and the m2m data immediately.
self.instance.save()
self._save_m2m()
else:
# If not committing, add a method to the form to allow deferred
# saving of m2m data.
self.save_m2m = self._save_m2m
return self.instance
save.alters_data = True
class ModelForm(BaseModelForm, metaclass=ModelFormMetaclass):
pass
问题出在您的 super 通话中。不是复制传递给方法的变量，而是用默认值覆盖它们。改用这个
super().__init__( data=data, files=files, auto_id=auto_id, prefix=prefix,
initial=initial, error_class=error_class, label_suffix=label_suffix,
empty_permitted=empty_permitted, instance=instance, use_required_attribute=use_required_attribute,
renderer=renderer)
另一种选择是简单地捕获所有参数：
def __init__(self, *args, **kwargs):
super().__init__(*args, **kwargs)