Validate property against another with JSON Schema - json

Question

In the model below, "category_id" property should be required only if "detail" array is empty.
If "detail" array is not empty, "category_id" property is not required.
How can I do this with JSON Schema?
{
"description": "Expense model validation.",
"type": "object",
"properties": {
"description": {
"type": "string"
},
"category_id": {
"type": "string"
},
"detail": {
"type": "array",
"items": {
"description": "Expense detail",
"type": "object",
"properties": {
"description": {
"type": "string"
}
},
"required": [ "description" ]
}
}
},
"required": [ "description", "category_id" ]
}

Answer 1

You can use anyOf to check that either category_id is present, or detail is present and has at least one item.
{
"description": "Expense model validation.",
"type": "object",
"properties": {
"description": { "type": "string" },
"category_id": { "type": "string" },
"detail": {
"type": "array",
"items": {
"description": "Expense detail",
"type": "object",
"properties": {
"description": { "type": "string" }
},
"required": ["description"]
}
}
},
"required": ["description"],
"anyOf": [
{ "required": ["category_id"] },
{
"properties": {
"detail": { "minItems": 1 }
},
"required": ["detail"]
}
]
}