Shows how discriminator can be used

uom-swagger.yml

openapi: 3.0.3
info:
  title: Unit of measure
  description: Gives ratio
  version: "0.0.1"
servers:
  - url: 'https://uom.com/v1'
tags:
  - name: UOM
    description: Unit of measure

paths:
  /uom/convert/{systemOfMeasurement}:
    post:
      tags:
        - UOM
      summary: Convert Reading
      description: Convert a reading
      operationId: convertReading
      parameters:
        - $ref: '#/components/parameters/systemOfMeasurement'
      requestBody:
        description: Reading to convert.
        required: true
        content:
          application/json:
            schema:
              $ref: '#/components/schemas/Reading'
      responses:
        200:
          description: OK
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/Reading'

components:
  parameters:
    systemOfMeasurement:
      name: systemOfMeasurement
      in: path
      description: system of measurement
      required: true
      schema:
        type: string
        enum:
          - metric
          - usStandard
        example: metric

  schemas:
    UnitOfMeasure:
      type: object
      description: Base model for all units of measure in the platform.
      properties:
        type:
          type: string
          description: Available types of measurements.
          enum:
            - distance
            - volume
    DistanceUoM:
      description: |
        Distance unit of measure. Supported values are:
          * mi (mile);
          * km (kilometer).
      allOf:
        - $ref: '#/components/schemas/UnitOfMeasure'
        - type: object
          properties:
            value:
              type: string
              description: Unit of measure values.
              enum: [ km, mi ]
      example:
        type: 'distance'
        value: 'km'
    VolumeUoM:
      description: |
        Volume unit of measure. Supported values are:
          * L (liter);
          * gal (gallon).
      allOf:
        - $ref: '#/components/schemas/UnitOfMeasure'
        - type: object
          properties:
            value:
              type: string
              description: Allowed values for volume unit of measure.
              enum: [ L, gal ]
      example:
        type: volume
        value: L
    Reading:
      type: object
      description: Represent reading.
      properties:
        value:
          type: integer
          description: Reading data.
          example: 7
        unitOfMeasure:
          oneOf:
            - $ref: '#/components/schemas/DistanceUoM'
            - $ref: '#/components/schemas/VolumeUoM'
          discriminator:
            propertyName: type
            mapping:
              distance: '#/components/schemas/DistanceUoM'
              volume: '#/components/schemas/VolumeUoM'