Adam Matan Adam Matan - 4 months ago 16
Python Question

JSON Schema: validate a number-or-null value

Is there a way to enable a JSON schema property to be either a number or

null
?

I am building an API which contains a
heading
attribute. Can be a number between 0 (inclusive) and 360 (exclusive), or null, so the following inputs are OK:

{"heading": 5}
{"heading": 0}
{"heading": null}
{"heading": 12}
{"heading": 120}
{"heading": null}


And the following inputs are erroneous:

{"heading": 360}
{"heading": 360.1}
{"heading": -5}
{"heading": false}
{"heading": "X"}
{"heading": 1200}
{"heading": false}


Addendum:

anyOf
is clearly the right answer. Adding the full schema for clarity.

Schema



{
"$schema": "http://json-schema.org/draft-04/schema#",
"type": "object",
"additionalProperties": false,
"properties": {
"heading": {
"anyOf": [
{"type": "number"},
{"type": "null"}
]
}
}
}

Answer

In draft-04, you would use the anyOf directive:

{
  "anyOf": [
    {
      "type": "number",
      "minimum": 0,
      "maximum": 360,
      "exclusiveMaximum": true
    },
    {
      "type": "null"
    }
  ]
}

You could also use "type": ["number", "null"] as Adam suggests, but I think anyOf is cleaner (as long as you use a draft-04 implementation), and ties the minimum and maximum declaration to the number explicitly.

Disclaimer: I don't know anything about the python implementation, my answer is about json schema.