One to ManyΒΆ

The one to many relationship is similar to the may to one relationship except that the role of the child and parent is swapped.

See also

One to Many

OpenAlchemy documentation for one to many relationships.

SQLAlchemy One to Many

SQLAlchemy documentation for one to many relationships.

The following example defines a one to many relationship between Employee and Division:

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
openapi: "3.0.0"

info:
  title: Test Schema
  description: API to illustrate One to Many Relationships.
  version: "0.1"

paths:
  /division:
    get:
      summary: Used to retrieve all divisions.
      responses:
        200:
          description: Return all divisions from the database.
          content:
            application/json:
              schema:
                type: array
                items:
                  "$ref": "#/components/schemas/Division"
  /employee:
    get:
      summary: Used to retrieve all employees.
      responses:
        200:
          description: Return all employees from the database.
          content:
            application/json:
              schema:
                type: array
                items:
                  "$ref": "#/components/schemas/Employee"

components:
  schemas:
    Division:
      description: A part of a company.
      type: object
      x-tablename: division
      properties:
        id:
          type: integer
          description: Unique identifier for the division.
          example: 0
          x-primary-key: true
        name:
          type: string
          description: The name of the division.
          example: Engineering
        employees:
          type: array
          items:
            "$ref": "#/components/schemas/Employee"
          description: The employees working in the division.
    Employee:
      description: Person that works for a company.
      type: object
      x-tablename: employee
      properties:
        id:
          type: integer
          description: Unique identifier for the employee.
          example: 0
          x-primary-key: true
        name:
          type: string
          description: The name of the employee.
          example: David Andersson

The following file uses OpenAlchemy to generate the SQLAlchemy models:

1
2
3
from open_alchemy import init_yaml

init_yaml("example-spec.yml", models_filename="models_auto.py")

The SQLAlchemy models generated by OpenAlchemy are equivalent to the following traditional models file:

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21
22
import sqlalchemy as sa
from sqlalchemy.ext.declarative import declarative_base

Base = declarative_base()


class Division(Base):
    """Division of a company."""

    __tablename__ = "division"
    id = sa.Column(sa.Integer, primary_key=True)
    name = sa.Column(sa.String)
    employees = sa.orm.relationship("Employee")


class Employee(Base):
    """Person that works for a company."""

    __tablename__ = "employee"
    id = sa.Column(sa.Integer, primary_key=True)
    name = sa.Column(sa.String)
    division_id = sa.Column(sa.Integer, sa.ForeignKey("division.id"))

OpenAlchemy will generate the following typed models:

  1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
"""Autogenerated SQLAlchemy models based on OpenAlchemy models."""
# pylint: disable=no-member,super-init-not-called,unused-argument

import typing

import sqlalchemy
from sqlalchemy import orm

from open_alchemy import models

Base = models.Base  # type: ignore


class DivisionDict(typing.TypedDict, total=False):
    """TypedDict for properties that are not required."""

    id: typing.Optional[int]
    name: typing.Optional[str]
    employees: typing.Sequence["EmployeeDict"]


class TDivision(typing.Protocol):
    """
    SQLAlchemy model protocol.

    A part of a company.

    Attrs:
        id: Unique identifier for the division.
        name: The name of the division.
        employees: The employees working in the division.

    """

    # SQLAlchemy properties
    __table__: sqlalchemy.Table
    __tablename__: str
    query: orm.Query

    # Model properties
    id: "sqlalchemy.Column[typing.Optional[int]]"
    name: "sqlalchemy.Column[typing.Optional[str]]"
    employees: 'sqlalchemy.Column[typing.Sequence["TEmployee"]]'

    def __init__(
        self,
        id: typing.Optional[int] = None,
        name: typing.Optional[str] = None,
        employees: typing.Optional[typing.Sequence["TEmployee"]] = None,
    ) -> None:
        """
        Construct.

        Args:
            id: Unique identifier for the division.
            name: The name of the division.
            employees: The employees working in the division.

        """
        ...

    @classmethod
    def from_dict(
        cls,
        id: typing.Optional[int] = None,
        name: typing.Optional[str] = None,
        employees: typing.Optional[typing.Sequence["EmployeeDict"]] = None,
    ) -> "TDivision":
        """
        Construct from a dictionary (eg. a POST payload).

        Args:
            id: Unique identifier for the division.
            name: The name of the division.
            employees: The employees working in the division.

        Returns:
            Model instance based on the dictionary.

        """
        ...

    @classmethod
    def from_str(cls, value: str) -> "TDivision":
        """
        Construct from a JSON string (eg. a POST payload).

        Returns:
            Model instance based on the JSON string.

        """
        ...

    def to_dict(self) -> DivisionDict:
        """
        Convert to a dictionary (eg. to send back for a GET request).

        Returns:
            Dictionary based on the model instance.

        """
        ...

    def to_str(self) -> str:
        """
        Convert to a JSON string (eg. to send back for a GET request).

        Returns:
            JSON string based on the model instance.

        """
        ...


Division: typing.Type[TDivision] = models.Division  # type: ignore


class EmployeeDict(typing.TypedDict, total=False):
    """TypedDict for properties that are not required."""

    id: typing.Optional[int]
    name: typing.Optional[str]


class TEmployee(typing.Protocol):
    """
    SQLAlchemy model protocol.

    Person that works for a company.

    Attrs:
        id: Unique identifier for the employee.
        name: The name of the employee.

    """

    # SQLAlchemy properties
    __table__: sqlalchemy.Table
    __tablename__: str
    query: orm.Query

    # Model properties
    id: "sqlalchemy.Column[typing.Optional[int]]"
    name: "sqlalchemy.Column[typing.Optional[str]]"

    def __init__(
        self, id: typing.Optional[int] = None, name: typing.Optional[str] = None
    ) -> None:
        """
        Construct.

        Args:
            id: Unique identifier for the employee.
            name: The name of the employee.

        """
        ...

    @classmethod
    def from_dict(
        cls, id: typing.Optional[int] = None, name: typing.Optional[str] = None
    ) -> "TEmployee":
        """
        Construct from a dictionary (eg. a POST payload).

        Args:
            id: Unique identifier for the employee.
            name: The name of the employee.

        Returns:
            Model instance based on the dictionary.

        """
        ...

    @classmethod
    def from_str(cls, value: str) -> "TEmployee":
        """
        Construct from a JSON string (eg. a POST payload).

        Returns:
            Model instance based on the JSON string.

        """
        ...

    def to_dict(self) -> EmployeeDict:
        """
        Convert to a dictionary (eg. to send back for a GET request).

        Returns:
            Dictionary based on the model instance.

        """
        ...

    def to_str(self) -> str:
        """
        Convert to a JSON string (eg. to send back for a GET request).

        Returns:
            JSON string based on the model instance.

        """
        ...


Employee: typing.Type[TEmployee] = models.Employee  # type: ignore