How sqlmodel works with FastApi in responses

[dkurchigin]

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Example Code

class CardTagLink(SQLModel, table=True):
    card_id: int | None = Field(default=None, foreign_key="card.id", primary_key=True)
    tag_id: int | None = Field(default=None, foreign_key="tag.id", primary_key=True)

class CardProjectLink(SQLModel, table=True):
    card_id: int | None = Field(default=None, foreign_key="card.id", primary_key=True)
    project_id: int | None = Field(default=None, foreign_key="project.id", primary_key=True)

class Card(SQLModel, table=True):
    id: int | None = Field(default=None, primary_key=True)
    name: str
    text: str

    tags: list["Tag"] = Relationship(back_populates="cards", link_model=CardTagLink, sa_relationship_kwargs={"lazy": "selectin"})
    projects: list["Project"] = Relationship(back_populates="cards", link_model=CardProjectLink, sa_relationship_kwargs={"lazy": "selectin"})

class Tag(SQLModel, table=True):
    id: int | None = Field(default=None, primary_key=True)
    name: str

    cards: list["Card"] = Relationship(back_populates="tags", link_model=CardTagLink)

class Project(SQLModel, table=True):
    id: int | None = Field(default=None, primary_key=True)
    name: str

    cards: list["Card"] = Relationship(back_populates="projects", link_model=CardProjectLink)

# my repo

class Repository:
    model: SQLModel

    def __init__(self, session):
        self.session = session

    def get_one(self, id_: int) -> 'SQLModel':
        statement = select(self.model).where(self.model.id == id_)
        return self.session.exec(statement).one()


# my schemas

class BaseResponseSchema(BaseModel):
    status: str = "OK"
    status_code: int = HTTP_200_OK
    message: str | None = None
    result: Any = None

class CardBaseSchema(BaseResponseSchema):
    result: Card

# my endpoint

@router.get("/cards/{card_id}")
async def read_card(card_id: int, db_client: DBClient = Depends(get_db_client)) -> CardBaseSchema:
    return CardBaseSchema(
        result=db_client.card.get_one(id_=card_id)
    )

Description

With my app i got result:
{"status":"OK","status_code":200,"message":null,"result":{"id":13,"name":"string","text":"string"}}

My card has tags and projects but i don't see them in response.
How can i show them?

Operating System

Linux

Operating System Details

Ubuntu 24.04.2 LTS

SQLModel Version

0.0.27

Python Version

Python 3.12.11

Additional Context

No response

[YuriiMotov]

Have you tried following the docs?
The first thing I noticed is that you are using "table" model (with table=True) as a part of response model. You shouldn't use table-models for validation.

Create CardBase model with common fields (excluding relationships), then create Card(CardBase, table=True) and add relationships to it, then create CardOutput(CardBase) and duplicate tags: list["Tag"] and projects: list["Project"] (without Relationship). Use CardOutput in CardBaseSchema.

BTW, looking at the output you provided, it looks like you were using BaseResponseSchema as response model that time.

[dkurchigin]

Thx, @YuriiMotov i missed it https://sqlmodel.tiangolo.com/tutorial/fastapi/multiple-models/#the-herocreate-data-model