DRF源码-fields.py
Posted jabbok
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https://www.cnblogs.com/pyspark/p/8607801.html
https://www.cnblogs.com/LYliangying/articles/9896548.html
fieids.py主要定义了各种字段的序列化类。Field是基类。
class Field
_creation_counter = 0 default_error_messages = ‘required‘: _(‘This field is required.‘), ‘null‘: _(‘This field may not be null.‘) default_validators = [] #默认验证器初始化为空list default_empty_html = empty initial = None
# 在构造函数中,给出了各种定义参数,由子类继承,在实例化时传参,来控制这个字段的各种属性 # read_only,表明只用于序列化输出 # write_only, 表明只用于反序列化输入,比如密码 # required, 表明在反序列化时必须输入 # default, 反序列化时使用的默认值 # initial # source, # label, 用于HTML展示API页面时,显示的字段名称 # help_text, 用于HTML展示API页面时,显示的字段帮助提示信息 # style # error_messages, 包含错误编号与错误信息的字典 # validators, 该字段使用的验证器 # allow_null, 表明该字段是否允许传入None,默认False def __init__(self, read_only=False, write_only=False, required=None, default=empty, initial=empty, source=None, label=None, help_text=None, style=None, error_messages=None, validators=None, allow_null=False): self._creation_counter = Field._creation_counter Field._creation_counter += 1 # If `required` is unset, then use `True` unless a default is provided. if required is None: required = default is empty and not read_only # Some combinations of keyword arguments do not make sense. # 断言一些没有意义的参数组合 assert not (read_only and write_only), NOT_READ_ONLY_WRITE_ONLY assert not (read_only and required), NOT_READ_ONLY_REQUIRED assert not (required and default is not empty), NOT_REQUIRED_DEFAULT assert not (read_only and self.__class__ == Field), USE_READONLYFIELD # 将传入的参数赋值给实例(属性初始化) self.read_only = read_only self.write_only = write_only self.required = required self.default = default self.source = source self.initial = self.initial if (initial is empty) else initial self.label = label self.help_text = help_text self.style = if style is None else style self.allow_null = allow_null if self.default_empty_html is not empty: if default is not empty: self.default_empty_html = default if validators is not None: self.validators = list(validators) # These are set up by `.bind()` when the field is added to a serializer. self.field_name = None self.parent = None # Collect default error message from self and parent classes messages = for cls in reversed(self.__class__.__mro__): messages.update(getattr(cls, ‘default_error_messages‘, )) messages.update(error_messages or ) self.error_messages = messages
# .validators is a lazily loaded property, that gets its default # value from `get_validators`. # validators属性设置 @property def validators(self): if not hasattr(self, ‘_validators‘): self._validators = self.get_validators() return self._validators @validators.setter def validators(self, validators): self._validators = validators def get_validators(self): return list(self.default_validators)
子类
class IntegerField(Field): default_error_messages = ‘invalid‘: _(‘A valid integer is required.‘), ‘max_value‘: _(‘Ensure this value is less than or equal to max_value.‘), ‘min_value‘: _(‘Ensure this value is greater than or equal to min_value.‘), ‘max_string_length‘: _(‘String value too large.‘) MAX_STRING_LENGTH = 1000 # Guard against malicious string inputs. re_decimal = re.compile(r‘\\.0*\\s*$‘) # allow e.g. ‘1.0‘ as an int, but not ‘1.2‘ def __init__(self, **kwargs): # 从变长传参里找max_value,min_value,给到实例,默认为None #继承父类的其他属性(相当于父类属性是通用,这里的属性是子类独有的) self.max_value = kwargs.pop(‘max_value‘, None) self.min_value = kwargs.pop(‘min_value‘, None) super().__init__(**kwargs) # 如果传参max_value,先拼接error message,然后在validators属性里添加一个验证器元素。 if self.max_value is not None: message = lazy_format(self.error_messages[‘max_value‘], max_value=self.max_value) self.validators.append( MaxValueValidator(self.max_value, message=message)) if self.min_value is not None: message = lazy_format(self.error_messages[‘min_value‘], min_value=self.min_value) self.validators.append( MinValueValidator(self.min_value, message=message)) def to_internal_value(self, data): if isinstance(data, str) and len(data) > self.MAX_STRING_LENGTH: self.fail(‘max_string_length‘) try: data = int(self.re_decimal.sub(‘‘, str(data))) except (ValueError, TypeError): self.fail(‘invalid‘) return data def to_representation(self, value): return int(value)
class CharField(Field): default_error_messages = ‘invalid‘: _(‘Not a valid string.‘), ‘blank‘: _(‘This field may not be blank.‘), ‘max_length‘: _(‘Ensure this field has no more than max_length characters.‘), ‘min_length‘: _(‘Ensure this field has at least min_length characters.‘), initial = ‘‘ def __init__(self, **kwargs): self.allow_blank = kwargs.pop(‘allow_blank‘, False) self.trim_whitespace = kwargs.pop(‘trim_whitespace‘, True) self.max_length = kwargs.pop(‘max_length‘, None) self.min_length = kwargs.pop(‘min_length‘, None) super().__init__(**kwargs) if self.max_length is not None: message = lazy_format(self.error_messages[‘max_length‘], max_length=self.max_length) self.validators.append( MaxLengthValidator(self.max_length, message=message)) if self.min_length is not None: message = lazy_format(self.error_messages[‘min_length‘], min_length=self.min_length) self.validators.append( MinLengthValidator(self.min_length, message=message)) # ProhibitNullCharactersValidator is None on Django < 2.0 if ProhibitNullCharactersValidator is not None: self.validators.append(ProhibitNullCharactersValidator()) def run_validation(self, data=empty): # Test for the empty string here so that it does not get validated, # and so that subclasses do not need to handle it explicitly # inside the `to_internal_value()` method. if data == ‘‘ or (self.trim_whitespace and str(data).strip() == ‘‘): if not self.allow_blank: self.fail(‘blank‘) return ‘‘ return super().run_validation(data) # 将int,float转为为str def to_internal_value(self, data): # We‘re lenient with allowing basic numerics to be coerced into strings, # but other types should fail. Eg. unclear if booleans should represent as `true` or `True`, # and composites such as lists are likely user error. if isinstance(data, bool) or not isinstance(data, (str, int, float,)): self.fail(‘invalid‘) value = str(data) return value.strip() if self.trim_whitespace else value def to_representation(self, value): return str(value)
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