Have one property define the types in another array property, using JSON Schema? - jsonschema

Question

Given this example JSON:
{
"type": "number",
"values": [ 34, 42, 99 ]
}
Is it possible to define JSON Schema that makes sure that the contents of
the values array are of the type specified in another property (in this example type)?
Above type is saying that the array values can only contain integers (using the specifier "number").
Or specify that values contains strings:
{
"type": "string",
"values": [ "hello", "world" ]
}

Answer 1

Yes you can use the "items" keyword. If it has a single value then that value is the schema for every element of the array.
{
"type": "array",
"items": { "type: "string" }
}
Assuming you're using a draft4 schema like most people do, section 8.2.3.1 of the specification states:
8.2.3.1. If "items" is a schema
If items is a schema, then the child instance must be valid against
this schema, regardless of its index, and regardless of the value of
"additionalItems".

Answer 2

Yes, but you will have to write an if/then block for each type you want to support.
The Understanding JSON Schema has a section on if/then/else: http://json-schema.org/understanding-json-schema/reference/conditionals.html
Here is an extract that explains how if/then/else works.
For example, let’s say you wanted to write a schema to handle
addresses in the United States and Canada. These countries have
different postal code formats, and we want to select which format to
validate against based on the country. If the address is in the United
States, the postal_code field is a “zipcode”: five numeric digits
followed by an optional four digit suffix. If the address is in
Canada, the postal_code field is a six digit alphanumeric string where
letters and numbers alternate.
{
"type": "object",
"properties": {
"street_address": {
"type": "string"
},
"country": {
"enum": ["United States of America", "Canada"]
}
},
"if": {
"properties": { "country": { "const": "United States of America" } }
},
"then": {
"properties": { "postal_code": { "pattern": "[0-9]{5}(-[0-9]{4})?" } }
},
"else": {
"properties": { "postal_code": { "pattern": "[A-Z][0-9][A-Z] [0-9][A-Z][0-9]" } }
}
}
For each type you want to support, you would need to write if/then object, and wrap all of them in an allOf.