JSON Schema difference between Array and Hash array

[Bloody Curse]

Hello there. I have the following array:

  "items": {
            "title": "Items",
            "type": "array",
            "items": {
                "title": "Item ",
                "type": "object",
            }
        }

Now, this is a normal Array right? How would a hash array look like? Or is that a hash array? If yes, how would a normal array look like?

[Jason Desrosiers]

Yes, your example would describe a 0-indexed array.  You can use an object to describe a hash.  The simplest version would be `{}`.  This works because the default `type` is `object` and the default `additionalProperties` is `true`.

{
  "title": "Items",
  "type": "object",
  "additionalProperties": true
}

This defines an object with any properties that have any value.  Effectively a hash.  You can restrict what values are allowed by using a schema instead of a boolean for `additionalProperties`.

{
  "title": "Items".
  "type": "object",
  "additionalProperties": {

    "title": "Item",
    "type": "object"
  }
}

This says that the values of the hash must be objects.  Actually, this effectively describes a hash of hashes.  You can also restrict the values of the keys of the hash using `patternProperties`.

{
  "title": "Items",
  "type": "object",
  "patternProperties": {
    "[A-Z][A-Z]": {

      "title": "Item",
      "type": "object"
    }
  }
}

This would restrict keys of the hash to be two capital letters (like state abbreviations for example).  Values would be hashes.

[Austin Wright]

It might be helpful to get some vocabulary out of the way first...

The example you have posted, at least in JSON terms, is part of an object, a kind of unordered key-value map. It would normally be found inside curly braces: {"a":1, "b":2, "c":3}

There's also arrays, a kind of vector of ordered items. They're found inside square brackets: [1, 2, 3]

I would stay away from the term "hash", which is short for "hash table", a particular implementation of a key-value map. There's no guarantee that the implementation you're using is going to be a hash table, it's just as likely to be a btree or similar kind of map that has different performance characteristics for lookup and writing.

Austin.

[Jason Desrosiers]

Austin, this type of data structure has many names in different programming languages.  They are called Map (Java), Dictionary (Python), associative array (PHP), object (JavaScript), Hash (Ruby), and probably more.  I agree that it is unfortunate that the term hash is ambiguous, but if that is the name the language uses, that is the best term to use in that context.  I assumed he was working in a context where hash is the appropriate term and used that term to describe it's equivalent in the context of json-schema.  It is best to use the appropriate name for the context you are in even if the name is ambiguous and overloaded like hash or object.