Nested objects with unknown keys - how to specify?

[mgrosvenor]

Hi all! I'm new to JSON Schema. Having a great time with the quicktype tool building generators/parsers for JSON objects. I've come across a situation which I can't figure out how to model. I'm hoping for some advice.

The situation is something like this: I have an object, which is a container for a list of objects which are all identical. Each object has its own name. So one way to do with would be something like:

{
    "devices" : [ 
        {
             "name" : "dev1",
             ....
        },
        {
             "name" : "dev1",
             ....
        },
        ....
    ]
}        

The above would be quite easy to model in JSON Schema. The important bit would be something like:

{
    "type" : "array",
    "items" : {
          "type" : "object"
          "$ref" : "device.json"
     }
}

BUT ... this is not a very "canonical" JSON way to do things. What I'd rather do is

{
    "devices" : {
         "dev1" : {
             ....
        },
        "dev2" : {
             ....
        },
        ...
}        

Where the key names "dev1" and "dev2" are completely arbitrary, but the object is same in every case. I can't figure out how to model this, because it seems that all the tools for modelling an object require me to have some knowledge of the property (key) names.

One idea I had was to use a PatternProperty where the pattern regex is simply .*, so any key will match. This would work I guess, but it seems like the wrong answer. This feels like a common enough situation that there should be some built in way to do this? Any ideas?

[gregsdennis]

I think you want to just specify additionalProperties, which just takes a schema. Often the false schema is used to indicate that there should be no properties other than the ones specified by the schema, but if you have arbitrary keys where the values must all be the same shape, then you can put the schema for the values in this.

{
  "type": "object",
  "additionalProperties": { ... }
}

The meta-schemas actually do this for a number of properties, like $defs and properties where the keys can be anything, but the values need to be valid schemas.

[mgrosvenor]

That’s a brilliant suggestion. It never occurred to me that “additional properties” might be the only properties. Problem solved! Thanks!