How to specify a property as null or a reference?

Question

I have a json document in which a part can be either null or a subobject, like this:

[{
    \"owner\":null    
},
{
    \"owner\":{
        \"id\":1
    }   
}]
         


        

Answer 1

What you've posted should work, if you remove the "type":"object" from the definition.

However, a neater, more explicit way to specify alternatives is to use oneOf. You can keep your "id" definition untouched, and just use:

    "owner":{
        "oneOf": [
            {"type": "null"},
            {"$ref":"#/definitions/id"}
        ]
    }

Answer 2

nullable field will be supported in OpenApi (aka Swagger) Specification v3.0.0

So with this new spec your definition would look like:

"properties":{
    "owner":{
        "nullable": true,
         ...
    }
},