sqlalchemy-nest 1.2.3
easy create nested models for sqlalchemy
License: MIT
Requires Python: <4.0,>=3.9
Keywords: sqlalchemy, nest, sqlalchemy-nest

# sqlalchemy-nest

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sqlalchemy-nest is easy create nested models for sqlalchemy

### Why?? 🧐🧐

The default constructor of ```declarative_base()``` in sqlalchemy is as follows

```python
def _declarative_constructor(self: Any, **kwargs: Any) -> None:
    cls_ = type(self)
    for k in kwargs:
        if not hasattr(cls_, k):
            raise TypeError(
                "%r is an invalid keyword argument for %s" % (k, cls_.__name__)
            )
        setattr(self, k, kwargs[k])

```

So can’t create nested model by unpacking schema like below. OMG !!!

```python
from sqlalchemy import Column, ForeignKey, Integer, String
from sqlalchemy.orm import declarative_base, relationship

Base = declarative_base()

class Root(Base):
    __tablename__ = "root"

    id = Column(Integer, primary_key=True, autoincrement=True)
    name = Column(String(100))

    branches = relationship("Branch", back_populates="root", uselist=True, lazy="joined")

class Branch(Base):
    __tablename__ = "branch"

    id = Column(Integer, primary_key=True, autoincrement=True)
    name = Column(String(100))
    root_id = Column(Integer, ForeignKey("root.id"))

    root = relationship("Root")

root = {
    'name': 'root',
    'branches': [
        {
            'name': 'branch',
        },
    ]
}

created_root = Root(**root)
>>> AttributeError: 'dict' object has no attribute '_sa_instance_state'
```


### Installation

```
pip install sqlalchemy-nest
```

### Create Nested Model

1. Set declarative_base constructor

    use ```declarative_nested_model_constructor``` for declarative_base constructor

    ```python
    from sqlalchemy import Column, ForeignKey, Integer, String
    from sqlalchemy.orm import declarative_base, relationship
    from sqlalchemy_nest import declarative_nested_model_constructor

    Base = declarative_base(constructor=declarative_nested_model_constructor)

    class Root(Base):
        __tablename__ = "root"

        id = Column(Integer, primary_key=True, autoincrement=True)
        name = Column(String(100))

        branches = relationship("Branch", back_populates="root", uselist=True, lazy="joined")

    class Branch(Base):
        __tablename__ = "branch"

        id = Column(Integer, primary_key=True, autoincrement=True)
        name = Column(String(100))
        root_id = Column(Integer, ForeignKey("root.id"))

        root = relationship("Root")
    ```

1. Initialization from **kwargs

    sets attributes on the constructed instance using the names and values in kwargs.

    ```python
    root = {
        'name': 'root',
        'branches': [
            {
                'name': 'branch',
            },
        ]
    }
    >>> session.add(Root(**root))
    >>> session.commit()
    >>> added_root: Root = session.query(Root).filter(Root.id == 1).first()
    Root(id=1, name='root', branches=[
        Branch(id=1, name='branch', root_id=1)]
    )
    ```

### Merge Nested Model

1. Set declarative_base constructor and cls

    use ```declarative_nested_model_constructor```  and ```BaseModel``` for declarative_base

    ```python
    from sqlalchemy import Column, ForeignKey, Integer, String
    from sqlalchemy.orm import declarative_base, relationship
    from sqlalchemy_nest import declarative_nested_model_constructor
    from sqlalchemy_nest.orm import BaseModel

    Base = declarative_base(cls=BaseModel, constructor=declarative_nested_model_constructor)

    class Root(Base):
        __tablename__ = "root"

        id = Column(Integer, primary_key=True, autoincrement=True)
        name = Column(String(100))

        branches = relationship("Branch", back_populates="root", uselist=True, lazy="joined")

    class Branch(Base):
        __tablename__ = "branch"

        id = Column(Integer, primary_key=True, autoincrement=True)
        name = Column(String(100))
        root_id = Column(Integer, ForeignKey("root.id"))

        root = relationship("Root")

    ```

1. Update from **kwargs


    ```python
    root = {
        'name': 'root',
        'branches': [
            {
                'name': 'branch',
            },
        ]
    }
    >>> session.add(Root(**root))
    >>> session.commit()
    >>> added_root: Root = session.query(Root).filter(Root.id == 1).first()
    Root(id=1, name='root', branches=[
        Branch(id=1, name='branch', root_id=1)]
    )

    update_root = {
        'id': 1,
        'name': 'updated_root',
        'branches': [
            {
                'id': 1,
                'name': 'updated_branch',
            },
            {
                'name': 'created_branch',
            },
        ]
    }
    >>> added_root.merge(**update_root)
    >>> session.commit()
    >>> updated_root: Root = session.query(Root).filter(Root.id == 1).first()
    Root(id=1, name='updated_root', branches=[
        Branch(id=1, name='updated_branch', root_id=1),
        Branch(id=2, name='created_branch', root_id=1)]
    )
    ```

### Development

Please refer to the [CONTRIBUTING](https://github.com/satorudev976/sqlalchemy-nest/blob/main/CONTRIBUTING.md)

### Example

[Sample Code](https://github.com/satorudev976/sqlalchemy-nest/tree/main/examples) using FastAPI and SQLAlchemy