How to use Switch in JSON Schema 6 with multiple IFs

Question

I have entity which is of array. I want to call different entity types based on a property called dataStoreType. My Schema looks like this:

"entities":{
  "type":"array",
  "switch":[
    {
      "if": {"properties":{"dataStoreType":"RELATIONAL"}},
      "then":{"$ref": "#/definitions/entities-relational"}
    },
    {
      "if": {"properties":{"dataStoreType":"DOCUMENT"}},
      "then":{"$ref": "#/definitions/entities-no-sql"}
    },
    {
      "if": {"properties":{"dataStoreType":"KEYVALUE"}},
      "then":{"$ref": "#/definitions/entities-key-value"}
    }
  ]
}

My instance JSON looks like this:

{
    "name": "document-simple",
    "dataStoreType": "RELATIONAL",
    "entities": [
        {
            "name": "Employee",
            "attributes": [
                {
                    "name": "firstName",
                    "type": "STRING",
                    "required": true
                },
                {
                    "name": "lastName",
                    "type": "STRING"
                },
        }
    ]
}

But my Schema is not validating this instance correctly because I think there is some error in the switch. I am sure that JSON is not being validated because I have defined other rules for entities(which I have not mentioned) and when my instance violates that, the schema is not showing error.

What could be the error in my switch

Answer 1

JSON Schema Draft 6 does not support the "if" and "then" keywords. It is currently a proposal. Probably you use an implementation which already supports it (ajv, maybe?).

On the other hand you can achieve what you want using "oneOf" and "const" in the following way:

{
    "oneOf" : [
        {
            "type": "object",
            "properties": {
                "dataStoreType": {
                    "const": "RELATIONAL"
                },
                "entities": {
                    "type": "array",
                    "items": {    
                        "$ref": "#/definitions/entities-relational"
                    }
                }
            }
        },
        {
            "type": "object",
            "properties": {
                "dataStoreType": {
                    "const": "DOCUMENT"
                },
                "entities": {
                    "type": "array",
                    "items": {    
                        "$ref": "#/definitions/entities-no-sql"
                    }
                }
            }
        },
        // and here comes the KEYVALUE schema.. I think you get it now
    ]
}

Answer 2

Your main problem is that where you have:

"properties": {"dataStoreType": "RELATIONAL"}

what you actually need is:

"properties": {"dataStoreType": {"const": "RELATIONAL"}}

Beyond that, note that switch is no longer a JSON Schema proposal, but if/then/else has been accepted for the next draft (draft-07). So when using Ajv or another validator with early if support turned on, or moving to draft-07 when it is out and supported, you want:

"entities":{
  "type":"array",
  "oneOf": [
    {
      "if": {"properties":{"dataStoreType":{"const":"RELATIONAL"}}},
      "then":{"$ref": "#/definitions/entities-relational"}
    },
    {
      "if": {"properties":{"dataStoreType":{"const":"DOCUMENT"}}},
      "then":{"$ref": "#/definitions/entities-no-sql"}
    },
    {
      "if": {"properties":{"dataStoreType":{"const":"KEYVALUE"}}},
      "then":{"$ref": "#/definitions/entities-key-value"}
    }
  ]
}

This is the equivalent of a switch (without fall-through) or a chained set of else-ifs (which also works, but gets harder to read the more you chain).

Your if conditions are mutually exclusive, so oneOf is appropriate here and will do what you want.

I would definitely avoid using switch, as it has been pretty thoroughly rejected as a proposal for the standard. It is unlikely to ever be added.