JSON Schema: How to check that an array contains at least one object with a property with a given value?

Question

How can I check in the following json that at least one element in the array names has a property nickName with the value Ginny?

{
  "names": [
    {
      "firstName": "Hermione",
      "lastName": "Granger"
    }, {
      "firstName": "Harry",
      "lastName": "Potter"
    }, {
      "firstName": "Ron",
      "lastName": "Weasley"
    }, {
      "firstName": "Ginevra",
      "lastName": "Weasley",
      "nickName": "Ginny"
    }
  ]
}

Currently I'm using the draft-06 version (FAQ here).

This is my NOT WORKING schema:

{
  "$schema": "http://json-schema.org/draft-06/schema#",
  "title": "Complex Array",
  "description": "Schema to validate the presence and value of an object within an array.",

  "type": "object",
  "properties": {
    "names": {
      "type": "array",
      "minItems": 1,
      "items": {
        "type": "object",
        "properties": {
          "firstName": {
            "type": "string"
          },
          "lastName": {
            "type": "string"
          },
          "nickName": {
            "type": "string"
          }
        },
        "anyOf": [
          {"required": ["nickName"]}
        ]
      }
    }
  }
}

Answer 1

I managed to figure it out using draft-06. On this version a new keyword contains was added. According to this draft specification:

contains

The value of this keyword MUST be a valid JSON Schema. An array instance is valid against "contains" if at least one of its elements is valid against the given schema.

Working schema:

{
  "$schema": "http://json-schema.org/draft-06/schema#",
  "title": "Complex Array",

  "type": "object",
  "properties": {
    "names": {
      "type": "array",
      "minItems": 1,
      "contains": {
        "type": "object",
        "properties": {
          "firstName": {
            "type": "string"
          },
          "lastName": {
            "type": "string"
          },
          "nickName": {
            "type": "string",
            "pattern": "^Ginny$"
          }
        },
        "required": ["nickName"]
      },
      "items": {
        "type": "object",
        "properties": {
          "firstName": {
            "type": "string"
          },
          "lastName": {
            "type": "string"
          },
          "nickName": {
            "type": "string"
          }
        }
      }
    }
  }
}