239 lines
6.2 KiB
Markdown
239 lines
6.2 KiB
Markdown
<a name="fields.base"></a>
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# fields.base
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<a name="fields.base.BaseField"></a>
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## BaseField Objects
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```python
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class BaseField(FieldInfo)
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```
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BaseField serves as a parent class for all basic Fields in ormar.
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It keeps all common parameters available for all fields as well as
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set of useful functions.
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All values are kept as class variables, ormar Fields are never instantiated.
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Subclasses pydantic.FieldInfo to keep the fields related
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to pydantic field types like ConstrainedStr
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<a name="fields.base.BaseField.is_valid_uni_relation"></a>
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#### is\_valid\_uni\_relation
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```python
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| @classmethod
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| is_valid_uni_relation(cls) -> bool
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```
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Checks if field is a relation definition but only for ForeignKey relation,
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so excludes ManyToMany fields, as well as virtual ForeignKey
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(second side of FK relation).
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Is used to define if a field is a db ForeignKey column that
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should be saved/populated when dealing with internal/own
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Model columns only.
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**Returns**:
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`(bool)`: result of the check
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<a name="fields.base.BaseField.get_alias"></a>
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#### get\_alias
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```python
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| @classmethod
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| get_alias(cls) -> str
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```
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Used to translate Model column names to database column names during db queries.
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**Returns**:
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`(str)`: returns custom database column name if defined by user,
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otherwise field name in ormar/pydantic
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<a name="fields.base.BaseField.is_valid_field_info_field"></a>
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#### is\_valid\_field\_info\_field
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```python
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| @classmethod
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| is_valid_field_info_field(cls, field_name: str) -> bool
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```
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Checks if field belongs to pydantic FieldInfo
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- used during setting default pydantic values.
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Excludes defaults and alias as they are populated separately
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(defaults) or not at all (alias)
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**Arguments**:
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- `field_name (str)`: field name of BaseFIeld
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**Returns**:
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`(bool)`: True if field is present on pydantic.FieldInfo
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<a name="fields.base.BaseField.convert_to_pydantic_field_info"></a>
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#### convert\_to\_pydantic\_field\_info
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```python
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| @classmethod
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| convert_to_pydantic_field_info(cls, allow_null: bool = False) -> FieldInfo
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```
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Converts a BaseField into pydantic.FieldInfo
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that is later easily processed by pydantic.
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Used in an ormar Model Metaclass.
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**Arguments**:
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- `allow_null (bool)`: flag if the default value can be None
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or if it should be populated by pydantic Undefined
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**Returns**:
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`(pydantic.FieldInfo)`: actual instance of pydantic.FieldInfo with all needed fields populated
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<a name="fields.base.BaseField.default_value"></a>
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#### default\_value
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```python
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| @classmethod
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| default_value(cls, use_server: bool = False) -> Optional[FieldInfo]
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```
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Returns a FieldInfo instance with populated default
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(static) or default_factory (function).
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If the field is a autoincrement primary key the default is None.
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Otherwise field have to has either default, or default_factory populated.
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If all default conditions fail None is returned.
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Used in converting to pydantic FieldInfo.
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**Arguments**:
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- `use_server (bool)`: flag marking if server_default should be
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treated as default value, default False
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**Returns**:
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`(Optional[pydantic.FieldInfo])`: returns a call to pydantic.Field
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which is returning a FieldInfo instance
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<a name="fields.base.BaseField.get_default"></a>
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#### get\_default
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```python
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| @classmethod
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| get_default(cls, use_server: bool = False) -> Any
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```
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Return default value for a field.
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If the field is Callable the function is called and actual result is returned.
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Used to populate default_values for pydantic Model in ormar Model Metaclass.
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**Arguments**:
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- `use_server (bool)`: flag marking if server_default should be
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treated as default value, default False
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**Returns**:
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`(Any)`: default value for the field if set, otherwise implicit None
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<a name="fields.base.BaseField.has_default"></a>
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#### has\_default
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```python
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| @classmethod
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| has_default(cls, use_server: bool = True) -> bool
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```
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Checks if the field has default value set.
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**Arguments**:
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- `use_server (bool)`: flag marking if server_default should be
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treated as default value, default False
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**Returns**:
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`(bool)`: result of the check if default value is set
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<a name="fields.base.BaseField.is_auto_primary_key"></a>
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#### is\_auto\_primary\_key
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```python
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| @classmethod
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| is_auto_primary_key(cls) -> bool
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```
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Checks if field is first a primary key and if it,
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it's than check if it's set to autoincrement.
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Autoincrement primary_key is nullable/optional.
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**Returns**:
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`(bool)`: result of the check for primary key and autoincrement
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<a name="fields.base.BaseField.construct_constraints"></a>
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#### construct\_constraints
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```python
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| @classmethod
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| construct_constraints(cls) -> List
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```
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Converts list of ormar constraints into sqlalchemy ForeignKeys.
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Has to be done dynamically as sqlalchemy binds ForeignKey to the table.
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And we need a new ForeignKey for subclasses of current model
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**Returns**:
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`(List[sqlalchemy.schema.ForeignKey])`: List of sqlalchemy foreign keys - by default one.
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<a name="fields.base.BaseField.get_column"></a>
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#### get\_column
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```python
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| @classmethod
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| get_column(cls, name: str) -> sqlalchemy.Column
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```
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Returns definition of sqlalchemy.Column used in creation of sqlalchemy.Table.
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Populates name, column type constraints, as well as a number of parameters like
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primary_key, index, unique, nullable, default and server_default.
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**Arguments**:
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- `name (str)`: name of the db column - used if alias is not set
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**Returns**:
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`(sqlalchemy.Column)`: actual definition of the database column as sqlalchemy requires.
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<a name="fields.base.BaseField.expand_relationship"></a>
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#### expand\_relationship
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```python
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| @classmethod
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| expand_relationship(cls, value: Any, child: Union["Model", "NewBaseModel"], to_register: bool = True, relation_name: str = None) -> Any
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```
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Function overwritten for relations, in basic field the value is returned as is.
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For relations the child model is first constructed (if needed),
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registered in relation and returned.
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For relation fields the value can be a pk value (Any type of field),
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dict (from Model) or actual instance/list of a "Model".
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**Arguments**:
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- `value (Any)`: a Model field value, returned untouched for non relation fields.
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- `child (Union["Model", "NewBaseModel"])`: a child Model to register
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- `to_register (bool)`: flag if the relation should be set in RelationshipManager
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**Returns**:
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`(Any)`: returns untouched value for normal fields, expands only for relations
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