inheritance

Inheritance example

This example takes demonstrates how type inheritance and polymorphism can be used with PactFlow's BDCT feature.

Inheritance

For inheritance to work, you must use the discrimator to constrain and clarify the potential matching types.

In this case, we support polymorphism via two schemas - Dog and Cat.

      responses:
        "200":
          description: successful operation
          content:
            "application/json":
              schema:
                oneOf:
                  - $ref: '#/components/schemas/Cat'
                  - $ref: '#/components/schemas/Dog'
                discriminator:
                  propertyName: petType
                required:
                  - petType

In the Definition of the schemas, you can then create a parent type (e.g. Pet) and use the discriminator property to signal how to differentate the allowed subtypes.

components:
  schemas:
    Pet:
      type: object
      required:
        - petType
      properties:
        petType:
          type: string
          enum: [Cat, Dog] # You can either use an enum like this, or specify `const` values on the subschemas (used in the example)
    Cat:
      ... # the Cat specific fields
    Dog:
      ... # the Dog specific fields

Use of discriminator

There are following requirements and limitations of using discriminator keyword:

• mapping in discriminator object is not supported.
• "implicit" discriminator values are not supported.
• oneOf keyword must be present in the same schema.
• discriminator property should be required either on the top level, or in all oneOf subschemas.
• each oneOf subschema must have the properties keyword with discriminator property. The subschemas should be either inlined or * included as direct references (only $ref keyword without any extra keywords is allowed).
• schema for discriminator property in each oneOf subschema must be const or enum, with unique values across all subschemas.

Not meeting any of these requirements would fail schema compilation.