| keyword | signature | summary | kind | instance | specification | metaschema | index | introduced_in | related | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
$defs |
Object<String, Schema> |
This keyword is used in meta-schemas to identify the required and optional vocabularies available for use in schemas described by that meta-schema. |
|
|
-9 |
2019-09 |
|
The $defs keyword provides a standardized way to define reusable subschemas within a single schema document, promoting modularity, reducing code duplication, and improving schema organization. Each subschema within $defs has a unique name, acting as a location for referencing, without directly affecting validation; its value must be a valid JSON Schema.
{{<schema Schema that describes the age of a person>}}
{
"$schema": "https://json-schema.org/draft/2020-12/schema",
"type": "object",
"properties": {
"age": {
"$ref": "#/$defs/positiveInteger"
}
},
"$defs": {
"positiveInteger": {
"type": "integer",
"minimum": 0
}
}
}
{{}}
{{<instance-pass The instance has a valid "age" property that meets the requirement specified in the "/$defs/positiveInteger" subschema>}}
{ "age": 25 }
{{}}
{{<instance-fail A string is not an integer>}}
{ "age": "some_string" }
{{}}
{{<schema Schema for product data>}}
{
"type": "array",
"minItems": 1,
"items": { "$ref": "#/$defs/product" },
"$defs": {
"product": {
"type": "object",
"properties": {
"name": { "type": "string" },
"price": { "type": "number", "minimum": 0 }
}
}
}
}
{{}}
{{<instance-pass The instance has a valid array of objects with product data as described in the "/$defs/product" subschema>}}
[
{ "name": "T-shirt", "price": 19.99 },
{ "name": "Mug", "price": 8.50 }
]
{{}}
{{<instance-fail The array is empty, violating the "minItems" constraint requiring at least one product>}}
[]
{{}}
{{<schema Schema for book details>}}
{
"$schema": "https://json-schema.org/draft/2020-12/schema",
"$id": "https://example.com/books",
"type": "object",
"properties": {
"title": { "type": "string" },
"author": { "$ref": "#author" }
},
"required": [ "title", "author" ],
"$defs": {
"author": {
"$anchor": "author",
"type": "object",
"properties": {
"name": { "type": "string" },
"age": { "type": "integer" }
}
}
}
}
{{}}
{{<instance-pass Instance with the required properties is valid>}}
{
"title": "Fundamental Physics",
"author": {
"name": "John Doe",
"age": 55
}
}
{{}}
{{<instance-fail 'author' proeprty is required>}}
{
"title": "Fundamental Chemistry"
}
{{}}
- Note: JSON Pointer isn't the only way of accessing a subschema. You can also use the
$anchorkeyword to reference a subschema within$defs.